Contents

List of Figures . . .

. . .7

List of Tables . . .

. . .11

Preface

.13

Acknowledgments . . .

. .15

Abbreviations and Acronyms

. . .17

Definitions

.19

Standards and Organizations

. . .23

Executive Summary . . .

.27

Chapter 1—Housing History and Purpose

Introduction . . .

.1-1

Preurban Housing . . .

. . .1-1

Ephemeral Dwellings . . .

. . .1-1

Episodic Dwellings

.1-1

Periodic Dwellings . . .

. .1-1

Seasonal Dwellings

.1-2

Semipermanent Dwellings . . .

. .1-2

Permanent Dwellings . . .

. . .1-2

Urbanization . . .

.1-2

Trends in Housing . . .

. . .1-3

References . . .

. . .1-7

Additional Sources of Information . . .

. . .1-7

Chapter 2—Basic Principles of Healthy Housing

Introduction . . .

.2-1

Fundamental Physiologic Needs . . .

. .2-1

Fundamental Psychologic Needs

.2-3

Protection Against Disease . . .

. . .2-3

Protection Against Injury . . .

.2-5

Protection Against Fire

. .2-6

Fire Extinguishers

. .2-9

Protection Against Toxic Gases . . .

. . .2-9

References . . .

. . .2-9

Additional Sources of Information . . .

. . .2-11

Chapter 3—Housing Regulations

Introduction . . .

.3-1

History . . .

. .3-1

Zoning, Housing Codes, and Building Codes . . .

.3-2

Zoning and Zoning Ordinances . . .

.3-3

Exceptions to the Zoning Code

.3-5

Housing Codes . . .

.3-6

Building Codes . . .

.3-12

References . . .

. . .3-12

Additional Sources of Information . . .

. . .3-13

Healthy Housing Reference Manual

Chapter 4—Disease Vectors and Pests

Introduction . . .

.4-1

Disease Vectors and Pests . . .

.4-1

Rodents

. . .4-1

Cockroaches

. . .4-4

Fleas . . .

. . .4-6

Flies

. . .4-7

Termites

. . .4-8

Fire Ants . . .

. . .4-13

Mosquitoes . . .

.4-15

References . . .

. . .4-17

Chapter 5—Indoor Air Pollutants and Toxic Materials

Introduction . . .

.5-1

Indoor Air Pollution

.5-1

Biologic Pollutants . . .

. .5-1

Chemical Pollutants

. . .5-6

Toxic Materials

. .5-13

Asbestos

. . .5-13

Lead . . .

. . .5-15

Arsenic

.5-19

References . . .

. . .5-20

Chapter 6—Housing Structure

Introduction . . .

.6-1

New Housing Terminology

.6-1

Old Housing Terminology . . .

. .6-6

Foundation . . .

. .6-8

Vapor Barriers . . .

. . .6-10

Crawl Space Barriers

. . .6-10

Vapor Barriers for Concrete Slab Homes

. . .6-10

Wall and Ceiling Vapors

. . .6-10

House Framing . . .

. .6-10

Foundation Sills

. . .6-10

Flooring Systems . . .

. . .6-10

Studs

. .6-11

Interior Walls

. .6-11

Stairways . . .

. . .6-12

Windows

. .6-12

Doors . . .

. .6-13

Roof Framing . . .

. . .6-15

Rafters

.6-15

Collar Beam

. . .6-15

Purlin . . .

. .6-15

Ridge Board

. . .6-15

Hip

. . .6-15

Roof Sheathing . . .

.6-15

Dormer

. . .6-15

Contents

Roofs

. . .6-15

Asphalt Shingle . . .

.6-15

EPDM . . .

.6-15

Asphalt Built-up Roofs

.6-16

Coal Tar Pitch Built-up Roofs

. .6-16

Slate Roofs

.6-16

Tile Roofs . . .

. .6-16

Copper Roofs . . .

. .6-16

Galvanized Iron Roofs . . .

. .6-16

Wood Shingle Roofs

. . .6-16

Roof Flashing

. .6-16

Gutters and Leaders . . .

.6-16

Exterior Walls and Trim . . .

. .6-16

Putting It All Together . . .

. . .6-17

References . . .

. . .6-21

Additional Sources of Information . . .

. . .6-22

Chapter 7—Environmental Barriers

Introduction . . .

.7-1

Roof

. . .7-2

Insulation . . .

. . .7-3

Siding . . .

. . .7-3

Fiber Cement . . .

. .7-4

Brick

. .7-4

Stucco

.7-4

Vinyl

. .7-5

Asbestos

. . .7-5

Metal . . .

. .7-5

References

. .7-6

Chapter 8—Rural Water Supplies and Water-quality Issues

Introduction . . .

.8-1

Water Sources . . .

. . .8-1

Source Location

.8-2

Well Construction . . .

. . .8-3

Sanitary Design and Construction

. .8-4

Pump Selection . . .

.8-4

Dug and Drilled Wells . . .

. . .8-4

Springs

.8-6

Cisterns

. . .8-6

Disinfection of Water Supplies . . .

. . .8-7

Chlorine Carrier Solutions . . .

. .8-9

Routine Water Chlorination (Simple) . . .

. . .8-9

Well Water Shock Chlorination . . .

.8-9

Backflow, Back-siphonage, and Other Water Quality Problems

. . .8-9

Backflow . . .

. . .8-9

Back-siphonage . . .

.8-10

Other Water Quality Problems . . .

. .8-10

Healthy Housing Reference Manual

Protecting the Groundwater Supply . . .

. .8-10

References . . .

. . .8-11

Additional Sources of Information . . .

. . .8-12

Chapter 9—Plumbing

Introduction . . .

.9-1

Elements of a Plumbing System . . .

. .9-1

Water Service

. .9-1

Hot and Cold Water Main Lines . . .

. . .9-3

Water Heaters . . .

. .9-7

Drainage System . . .

. . .9-8

Corrosion Control . . .

. . .9-13

Water Conservation . . .

. .9-13

Putting It All Together . . .

. . .9-14

References . . .

. . .9-15

Additional Sources of Information . . .

. . .9-16

Chapter 10—On-site Wastewater Treatment

Introduction

. . .10-1

Treatment of Human Waste . . .

.10-1

On-site Wastewater Treatment Systems . . .

. .10-3

Septic Tank Systems

. .10-3

Alternative Septic Tank Systems . . .

. . .10-6

Maintaining the On-site Wastewater Treatment Systems

.10-8

Symptoms of Septic System Problems . . .

. .10-9

Septic Tank Inspection . . .

.10-9

References . . .

. .10-11

Additional Sources of Information

. .10-12

Chapter 11—Electricity

Introduction

. . .11-1

Flow of Electric Current

. . .11-2

Electric Service Entrance

. . .11-3

Service Drop . . .

. .11-3

Underground Service . . .

. .11-4

Electric Meter

.11-4

Grounding

.11-4

Two- or Three-wire Electric Services . . .

.11-6

Residential Wiring Adequacy . . .

. . .11-6

Wire Sizes and Types . . .

. . .11-7

Reducing Risk . . .

.11-7

Wire Sizes . . .

.11-7

Wire Types

. . .11-8

Types of Cable

.11-8

Flexible Cords . . .

. .11-9

The Problem . . .

. .11-9

The Standards . . .

.11-9

Contents

Safety Suggestions

.11-9

Wiring

.11-10

Open Wiring

.11-10

Concealed Knob and Tube Wiring . . .

.11-10

Electric Service Panel . . .

. . .11-10

Over-Current Devices

. .11-10

Circuit Breakers (Fuseless Service Panels)

. .11-11

Ground Fault Circuit Interrupters

.11-11

Arc-fault Circuit Interrupters . . .

. .11-12

Fused Ampere Service Panel (Fuse Box)

. . .11-12

Electric Circuits . . .

.11-13

Outlet Switches and Junction Boxes . . .

. . .11-13

Grounding Outlets

. . .11-13

Polarized Plugs and Connectors

. . .11-14

Common Electrical Violations . . .

. .11-14

Excessive or Faulty Fusing

.11-15

Cords Run Through Walls or Doorways and Hanging Cords or Wires . . .

. .11-15

Temporary Wiring . . .

.11-16

Excessively Long Extension Cords

.11-16

Dead or Dummy Outlets . . .

. .11-16

Aluminum Wiring Inside the Home . . .

. . .11-16

Inspection Steps

. . .11-16

References . . .

. .11-17

Additional Sources of Information

. .11-17

Chapter 12—Heating, Air Conditioning, and Ventilating

Introduction

. . .12-1

Heating . . .

.12-4

Standard Fuels . . .

.12-4

Central Heating Units . . .

.12-7

Space Heaters

.12-12

Hydronic Systems . . .

.12-14

Direct Vent Wall Furnaces . . .

.12-15

Cooling

. . .12-15

Air Conditioning . . .

. .12-15

Circulation Fans

. .12-16

Evaporation Coolers

. .12-16

Safety

. .12-17

Chimneys . . .

.12-17

Fireplaces

.12-18

References . . .

. .12-19

Additional Sources of Information

. .12-19

Chapter 13—Energy Efficiency

Introduction

. . .13-1

Energy Systems . . .

.13-1

R-values

. . .13-1

Healthy Housing Reference Manual

Roofs

. .13-2

Ridge Vents . . .

. .13-3

Fan-powered Attic Ventilation

. .13-3

White Roof Surface . . .

. .13-3

Insulation

. .13-3

Wall Insulation

. .13-4

Floor Insulation . . .

. .13-4

Doors . . .

. .13-5

Hot Water Systems

. .13-7

Windows

. .13-7

Caulking and Weather-stripping . . .

. .13-7

Replacing Window Frames . . .

. .13-7

Tinted Windows . . .

. .13-8

Reducing Heat Loss and Condensation

. .13-8

Glazing . . .

. .13-8

Layering

. .13-8

Other Options

. .13-9

Solar Energy

. .13-9

Active Solar Systems

. .13-9

Passive Solar Systems . . .

. .13-10

Conducting an Energy Audit . . .

. .13-10

References . . .

. .13-11

Additional Sources of Information

. .13-11

Chapter 14—Residential Swimming Pools and Spas

Introduction

. .14-1

Child-proofing

. .14-1

Hazards

. .14-2

Public Health Issues . . .

. .14-2

Diseases

. .14-3

Injuries

. .14-3

Water Testing Equipment

. .14-3

Disinfection

. .14-4

Content Turnover Rate

. .14-4

Filters

. .14-5

High-rate Sand Filters

. .14-5

Cartridge Filters

. .14-5

Diatomaceous Earth

. .14-5

Filter Loading Rates . . .

. .14-5

Disinfectants . . .

. .14-5

Effect of pH

. .14-6

Chlorine Disinfectants . . .

. .14-6

Pool Water Hardness and Alkalinity . . .

. .14-8

Liquid Chemical Feeders . . .

. .14-9

Positive Displacement Pump

. .14-9

Erosion and Flow-through Disinfectant Feeders

. . .14-10

Spas and Hot Tubs

.14-10

References . . .

. .14-11

Additional Sources of Information

. .14-11

Contents

List of Figures

Chapter 1—Housing History and Purpose

Figure 1.1.

Conditions in the Tenements

.1-3

Figure 1.2.

Levittown, New York

.1-6

Chapter 2—Basic Principles of Healthy Housing

Figure 2.1.

Circa 1890 Icebox

. . .2-5

Figure 2.2.

Smoke Alarm Testing

.2-8

Chapter 3—Housing Regulations

Figure 3.1.

Example of a Floor Area

. .3-5

Figure 3.2.

Example of an Angle of Light Obstruction . . .

.3-5

Chapter 4—Disease Vectors and Pests

Figure 4.1.

Field Identification of Domestic Rodents . . .

. .4-2

Figure 4.2.

Norway Rat . . .

. .4-2

Figure 4.3.

Roof Rat

.4-2

Figure 4.4.

Signs of Rodent Infestation . . .

. . .4-3

Figure 4.5.

Rodent Prevention

. . .4-4

Figure 4.6.

Live Trap for Rats . . .

.4-4

Figure 4.7.

Kill Traps . . .

.4-4

Figure 4.8.

American, Oriental, German, and Brown-banded Cockroaches . . .

.4-5

Figure 4.9.

American Cockroaches, Various Stages and Ages

. .4-5

Figure 4.10.

Oriental Cockroaches, Various Stages and Ages

. . .4-5

Figure 4.11.

German Cockroaches, Various Stages and Ages

. . .4-5

Figure 4.12.

Brown-banded Cockroaches, Various Stages and Ages

.4-5

Figure 4.13.

Wood Cockroach, Adult Male . . .

.4-5

Figure 4.14.

Reported Human Plague Cases (1970-1997) . . .

. .4-6

Figure 4.15.

Flea Life Cycle

. . .4-6

Figure 4.16.

Housefly (Musca domestica) . . .

. . .4-7

Figure 4.17.

Life Cycle of the Fly

. .4-8

Figure 4.18.

Termite Tube Extending From Ground to Wall

. . .4-9

Figure 4.19.

Termite Mud Shelter Tube Constructed Over A Brick Foundation

.4-9

Figure 4.20.

Differences Between Ants and Termites

. . .4-9

Figure 4.21.

Life Cycle of the Subterranean Termite

. . .4-10

Figure 4.22.

Subterranean Termite Risk in the United States

. . .4-11

Figure 4.23.

Typical Points of Attack by Termites in the Home

.4-12

Figure 4.24.

Construction Techniques That Discourage Termite Attacks . . .

.4-14

Figure 4.25.

Fire Ants

.4-14

Figure 4.26.

Range Expansion of Red Imported Fire Ants (RIFA) in the United States, 1918-1998

.4-15

Figure 4.27.

Fire Ant Mound . . .

. .4-15

Chapter 5—Indoor Air Pollutants and Toxic Materials

Figure 5.1.

Mold Growth in the Home . . .

. . .5-7

Figure 5.2.

Home Carbon Monoxide Monitor

. . .5-7

Figure 5.3.

Environmental Tobacco Smoke and Children’s Exposure . . .

. . .5-8

Figure 5.4.

Wood Products Label . . .

.5-10

Figure 5.5.

EPA Map of Radon Zones

. . .5-10

Figure 5.6.

Radon Entry

.5-11

Figure 5.7.

Home Radon Detectors

. .5-12

Healthy Housing Reference Manual

Figure 5.9.

Radon-resistant Construction . . .

.5-12

Figure 5.10. Arsenic Label. . .

.5-19

Chapter 6—Housing Structure

Figure 6.1.

Housing Structure Terminology, Typical House Built Today

. .6-1

Figure 6.2.

Housing Structure Terminology, Typical House Built Between 1950 and 1980 . . .

.6-6

Figure 6.3.

Foundation. . .

.6-9

Figure 6.4.

Foundation Cracks

. .6-9

Figure 6.5.

Interior Stairway

.6-12

Figure 6.6.

Classifications of Windows

. .6-12

Figure 6.7.

Three-dimensional View of a Window . . .

. . .6-13

Figure 6.8.

Window Details

.6-13

Figure 6.9.

Wall Framing. . .

.6-17

Chapter 7—Environmental Barriers

Figure 7.1.

Sources of Moisture and Air Pollutants . . .

. . .7-1

Figure 7.2.

Blown Attic Insulation . . .

. . .7-3

Figure 7.3.

Depth of Attic Insulation . . .

.7-3

Figure 7.4.

Attic Insulation . . .

. .7-3

Figure 7.5.

Brick Structural Defect

. .7-4

Figure 7.6.

Corrosion in Piping Resulting From Galvanic Response

. .7-5

Chapter 8—Rural Water Supplies

Figure 8.1.

U.S. Water Supply by Source . . .

.8-1

Figure 8.2.

Cross Section of a Driven Well . . .

. . .8-3

Figure 8.3.

Well Seal . . .

. .8-4

Figure 8.4.

Converted Dug Well . . .

.8-4

Figure 8.5.

Recapped and Sealed Dug Well

. .8-5

Figure 8.6.

Drilled Well. . .

.8-5

Figure 8.7.

Typical Dug Well

. . .8-5

Figure 8.8.

Sewage in Drainage Ditch . . .

. . .8-6

Figure 8.9.

Drilled Well. . .

.8-6

Figure 8.10. Spring Box. . .

. .8-6

Chapter 9—Plumbing

Figure 9.1.

Typical Home Water System

.9-1

Figure 9.2.

House Service Installation

. . .9-2

Figure 9.3.

Gas Water Heater

. . .9-7

Figure 9.4.

Temperature-pressure Valve

. .9-8

Figure 9.5.

Branch Connections

.9-10

Figure 9.6.

P-trap. . .

. . .9-10

Figure 9.7.

Types of S-traps . . .

. .9-10

Figure 9.8.

Trap Seal: (a) Seal Intact; (b) Fixture Draining; (c) Loss of Gas Seal . . .

. . .9-10

Figure 9.9.

Loss of Trap Seal in Lavatory Sink

. . .9-11

Figure 9.10. Back-to-back Venting (Toilet). . .

.9-11

Figure 9.11. Back-to-back Venting (Sink). . .

. .9-11

Figure 9.12. Wall-hung Fixtures

. .9-12

Figure 9.13. Unit Vent Used in Bathtub Installation

. .9-12

Figure 9.14. Toilet Venting. . .

. . .9-12

Figure 9.15. Janitor’s Sink. . .

.9-13

Figure 9.16. Common Y-trap. . .

. .9-13

Figure 9.17. Hose Bib With Vacuum Breaker

.9-13

List of Figures

Chapter 10—On-site Wastewater Treatment

Figure 10.1. Conventional On-site Septic System . . .

.10-1

Figure 10.2. Straight Pipe Discharge. . .

. .10-2

Figure 10.3. Clear Creek Water Contaminated With Sewage. . .

. .10-2

Figure 10.4. Septic Tank System

.10-3

Figure 10.5. Septic Tank. . .

. .10-4

Figure 10.6. On-site Sewage Disposal System Site Evaluation Form

. .10-5

Figure 10.7. Cross-section of an Absorption Field

. . .10-5

Figure 10.8. Mound System Cutaway

. . .10-7

Figure 10.9. Low Pressure On-site System . . .

. . .10-7

Figure 10.10. Plant-rock Filter System . . .

.10-8

Figure 10.11. Sludge and Scum in Multicompartment Septic Tank . . .

.10-10

Chapter 11—Electricity

Figure 11.1. Utility Overview

. . .11-3

Figure 11.2. Entrance Head. . .

. .11-3

Figure 11.3. Armored Cable Service Entrance

. . .11-4

Figure 11.4. Breakers. . .

.11-4

Figure 11.5. Thin-wall Conduit

.11-4

Figure 11.6. Electric Meter. . .

. . .11-5

Figure 11.7. Typical Service Entrance

. . .11-5

Figure 11.8. Grounding Scheme . . .

.11-6

Figure 11.9. Grounding. . .

.11-6

Figure 11.10. Three-wire Service . . .

. .11-7

Figure 11.11. Two-wire Service . . .

. . .11-7

Figure 11.12. Wire Markings. . .

. .11-8

Figure 11.13. Armored Cable.

. . .11-9

Figure 11.14.

200-Amp Service Box. . .

. . .11-11

Figure 11.15. External Power Shutoff and Meter

. .11-11

Figure 11.16. Ground Fault Circuit Interruptor . . .

. . .11-12

Figure 11.17. Arc Interrupter

.11-12

Figure 11.18. Types of Fuses. .

. . .11-13

Figure 11.19. Appliance Ground and Grounded Plug

.11-14

Chapter 12—Heating, Air Conditioning, and Ventilating

Figure 12.1. Heat Pump in Cooling Mode . . .

. . .12-5

Figure 12.2. Piping Hookup for Inside Tank Installation

.12-6

Figure 12.3. Piping Hookup for Buried Outside Tank

. . .12-6

Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm Air Furnace

. . .12-7

Figure 12.5.

Minimum Clearance for Steam or Hot Water Boiler and Mechanical Warm-air Furnace .12-7

Figure 12.6. Heating Ducts Covered With Asbestos Insulation . . .

. . .12-7

Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers . . .

. .12-8

Figure 12.8. Cutaway View of Typical High-pressure Gun Burner . . .

.12-9

Figure 12.9. Gas-fired Boiler . . .

.12-9

Figure 12.10. Typical Gravity One-pipe Heating System

. .12-10

Figure 12.11. One-pipe Gravity Water Heating System

. . .12-11

Figure 12.12. Two-pipe Gravity Water Heating System

. . .12-11

Figure 12.13. Warm-air Convection Furnace . . .

. .12-11

Figure 12.14. Cross-sectional View of Building Showing Forced-warm-air Heating System

.12-12

Figure 12.15. Perforated-sleeve Burner . . .

.12-13

Figure 12.16. Condition of Burner Flame With Different Rates of Fuel Flow

. .12-13

Figure 12.17. Wall and Ceiling Clearance Reduction . . .

. .12-14

Healthy Housing Reference Manual

List of Tables

Chapter 8—Rural Water Supplies and Water-quality Issues

Table 8.1.

Recommended Minimum Distance Between Well and Pollution Sources . . .

. .8-2

Table 8.2.

Types of Wells for Accessing Groundwater, Well Depths, and Diameters

. .8-3

Table 8.3.

Disinfection Methods

. . .8-7

Table 8.4.

Chlorination Guide for Specific Water Conditions

. . .8-8

Table 8.5.

Preparing a 200-ppm Chlorine Solution . . .

. .8-9

Table 8.6.

Analyzing and Correcting Water Quality Problems . . .

. . .8-11

Chapter 9—Plumbing

Table 9.1.

Fixture Unit Values

. .9-9

Table 9.2.

Sanitary House Drain Sizes

. .9-9

Table 9.3.

Minimum Fixture Service Pipe Diameters

. . .9-12

Chapter 10—On-site Wastewater Treatment

Table 10.1.

Mound System Advantages and Disadvantages

. .10-6

Table 10.2.

Low-pressure Pipe Systems Advantages and Disadvantages . . .

. . .10-7

Table 10.3.

Plant Rock Filter System Advantages and Disadvantages

.10-8

Table 10.4.

Septic Tank System Troubleshooting . . .

.10-10

Chapter 13—Energy Efficiency

Table 13.1.

Cost-effective Insulation R-values for Existing Homes . . .

. . .13-2

Table 13.2.

R-values of Roof Components . . .

. .13-3

Table 13.3.

Floor Insulation . . .

.13-5

Chapter 14—Residential Swimming Pools and Spas

Table 14.1.

Pool Water Quality Problem Solving

. . .14-7

Table 14.2.

pH Effect on Chlorine Disinfection . . .

.14-8

Table 14.3.

Chlorine Use in Swimming Pools . . .

. . .14-8

Table 14.4.

Swimming Pool Operating Parameters

. .14-9

Table 14.5.

Spa and Hot Tub Operating Parameters

.14-11

Healthy Housing Reference Manual

Preface

ousing quality is key to the public’s health. Translating that simple axiom into action is the topic of this book.

In the 30 years since the first edition was published, the nation’s understanding of how specific housing con-

ditions are related to disease and injury has matured and deepened. This new edition will enable public health

and housing professionals to grasp our shared responsibility to ensure that our housing stock is safe, decent, afford-

able, and healthy for our citizens, especially those who are particularly vulnerable and who spend more time in the

home, such as children and the elderly.

The Centers for Disease Control and Prevention and the U.S. Department of Housing and Urban Development

(HUD) have worked together with many others to discover the ways to eliminate substandard housing conditions that

harm health. For example, the advances in combating water borne diseases was possible, in part, through standardiza-

tion of indoor plumbing and sewage, and the institution of federal, state and local regulations and codes. Childhood

lead poisoning has been dramatically reduced, in part, through the elimination of residential lead-based paint hazards.

Other advances have been made to protect people from carbon monoxide poisoning, falls, safety hazards, electrocu-

tion, and many other risks.

However, more must be done to control existing conditions and to understand emerging threats that remain poorly

understood. For example, nearly 18 million Americans live with the health threat of contaminated drinking water

supplies, especially in rural areas where on-site wastewater systems are prevalent. Despite progress, thousands of chil-

dren still face the threat of lead poisoning from residential lead paint hazards. The increase in asthma in recent

decades and its relationship to housing conditions such as excess moisture, mold, settled dust allergens and ventilation

remains the subject of intense research. The impact of energy conservation measures on the home environment is still

unfolding. Simple affordable construction techniques and materials that minimize moisture problems and indoor air

pollution, improve ventilation, and promote durability and efficiency continue to be uncovered.

A properly constructed and maintained home is nearly timeless in its usefulness. A home is often the biggest single

investment people make. This manual will help to ensure that the investment is a sound one that promotes healthy

and safe living.

Home rehabilitation has increased significantly in the last few years and HUD has prepared a nine-part series, The

Rehab Guide, that can assist both residents and contractors in the rehabilitation process. For additional information,

go to http://www.huduser.org/publications/destech/rehabgui.html.

Healthy Housing Reference Manual

Acknowledgments

e acknowledge the suggestions, assistance, and review of numerous individuals and organizations that went

into the original and current versions of this manual. The revisions to this manual were made by a team of

environmental health, housing, and public health professionals led by Professor Joe Beck, Dr. Darryl

Barnett, Dr. Gary Brown, Dr. Carolyn Harvey, Professor Worley Johnson, Dr. Steve Konkel, and Professor Charles

Treser.

Individuals from the following organizations were involved in the various drafts of this manual:

• Department of Housing and Urban Development (HUD), Office of Healthy Homes and Lead Hazard

Control;

• U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC),

National Center for Environmental Health (NCEH);

• National Healthy Homes Training Center and Network;

• National Association of Housing and Redevelopment Officials;

• Department of Building, Housing and Zoning (Allentown, Pennsylvania);

• Code Enforcement Associates (East Orange, New Jersey);

• Eastern Kentucky University (Richmond, Kentucky);

• University of Washington; Seattle (Washington); and

• Battelle Memorial Institute (Columbus, Ohio).

Specifically, our gratitude goes to the following reviewers:

• Dr. David Jacobs, Martin Nee, and Dr. Peter Ashley, HUD;

• Pat Bohan, East Central University;

• James Larue, The House Mender Inc.;

• Ellen Tohn, ERT Associates;

• Dr. Stephen Margolis, Emory University; and

• Joseph Ponessa and Rebecca Morley, Healthy Homes Training Center.

A special thank-you for assistance from Carolyn Case-Compton, Habitat for Humanity, 123 East Main Street,

Morehead, Kentucky. Pictures of a home under construction are courtesy of Habitat for Humanity and John King,

home builder and instructor, Rowan County Technical College, Morehead, Kentucky; and Don W. Johnson, building

photographer of Habitat for Humanity.

In addition, a special thank you to CAPT Craig Shepherd and CAPT Michael Herring, Commissioned Corps, U.S.

Public Health Service, CDC/NCEH/Environmental Health Services Branch for their research and review during the

editing of this manual. Special thanks to Pamela S. Wigington and Joey L. Johnson for their hard work preparing this

manual for publication and to Teresa M. Sims for Web publication.

Healthy Housing Reference Manual

Abbreviations and Acronyms

ABS

acrylonitrile-butadiene-styrene

ADA

Americans with Disabilities Act

AGA

American Gas Association

ALA

American Lung Association

ANSI

American National Standards Institute

APHA

American Public Health Association

ASME

American Society of Mechanical Engineers

ASSE

American Society of Structural Engineers

ASTM

American Society for Testing Materials

ATSDR

Agency for Toxic Substances and Disease Registry

AWG

American Wire Gauge

AWWA

American Waters Works Association

BTU

British thermal unit

CDC

Centers for Disease Control and Prevention

CFR

Code of Federal Regulations

CGA

Canadian Gas Association

carbon monoxide

CPR

cardiopulmonary resuscitation

CPSC

Consumer Product Safety Commission

CSIA

Chimney Safety Institute of America

DDT

dichlorodiphenyltrichlorethane

diatomaceous earth

DPD

N,N-diethyl-p-phenylene diamine

DWV

drain, waste, and vent

EIFS

exterior insulation and finish system

EPA

U.S. Environmental Protection Agency

EPDM

ethylene propylene dieneterpolymer

ETS

environmental tobacco smoke

FHA

Federal Housing Administration

Factory Mutual

GFCI

ground fault circuit interrupter

HEPA

high-efficiency particulate air

HHS

Health and Human Services, U.S. Department of

HSC

Home Safety Council

HUD

Housing and Urban Development, U.S. Department of

HVAC

heating, ventilating and air conditioning

IAPMO

International Association of Plumbing and Mechanical Officials

ICC

International Code Council

IPM

integrated pest management

ISO

International Standard Organization

kilogram

LPP

low-pressure pipe

MPMH

Military Pest Management Handbook

MSS

Mechanical Standardization Society of the Valve and Fitting Industry

NCEH

National Center for Environmental Health

NCI

National Cancer Institute

NIA

National Institute on Aging

NSF

National Science Foundation

NTU

nephelometric turbidity unit

Healthy Housing Reference Manual

Definitions

Accessory building or structure: a detached building or structure in a secondary or subordinate capacity from the

main or principal building or structure on the same premises.

Appropriate authority/Authority having jurisdiction (AHJ): a person within the governmental structure of the

corporate unit who is charged with the administration of the appropriate code.

Ashes: the residue from burning combustible materials.

Attic: any story or floor of a building situated wholly or partly within the roof, and so designed, arranged, or built to

be used for business, storage, or habitation.

Basement: the lowest story of a building, below the main floor and wholly or partially lower than the surface of the ground.

Building: a fixed construction with walls, foundation, and roof, such as a house, factory, or garage.

Bulk container: any metal garbage, rubbish, or refuse container having a capacity of 2 cubic yards or greater and which is

equipped with fittings for hydraulic or mechanical emptying, unloading, or removal.

Central heating system: a single system supplying heat to one or more dwelling unit(s) or more than one rooming unit.

Chimney: a vertical masonry shaft of reinforced concrete, or other approved noncombustible, heat-resisting material

enclosing one or more flues, for the purpose of removing products of combustion from solid, liquid, or gaseous fuel.

Dilapidated: in a state of disrepair or ruin and no longer adequate for the purpose or use for which it was originally intended.

Dormitory: a building or a group of rooms in a building used for institutional living and sleeping purposes by four or

more persons.

Dwelling: any enclosed space wholly or partly used or intended to be used for living, sleeping, cooking, and eating.

(Temporary housing, as hereinafter defined, shall not be classified as a dwelling.) Industrialized housing and modular

construction that conform to nationally accepted industry standards and are used or intended for use for living,

sleeping, cooking, and eating purposes shall be classified as dwellings.

Dwelling unit: a room or group of rooms located within a dwelling forming a single habitable unit with facilities used

or intended to be used by a single family for living, sleeping, cooking, and eating.

Egress: arrangements and openings to assure a safe means of exit from buildings.

Extermination: the control and elimination of insects, rodents, or other pests by eliminating their harborage places;

by removing or making inaccessible materials that may serve as their food; by poisoning, spraying, fumigating,

trapping, or any other recognized and legal pest elimination methods approved by the local or state authority having

such administrative authority. Extermination is one of the components of integrated pest management.

Fair market value: a price at which both buyers and sellers will do business.

Family: one or more individuals living together and sharing common living, sleeping, cooking, and eating facilities

(See also Household).

Healthy Housing Reference Manual

Flush toilet: a toilet bowl that can be flushed with water supplied under pressure and that is equipped with a water-

sealed trap above the floor level.

Garbage: animal and vegetable waste resulting from handling, preparation, cooking, serving, and nonconsumption of food.

Grade: the finished ground level adjacent to a required window.

Guest: an individual who shares a dwelling unit in a nonpermanent status for not more than 30 days.

Habitable room: a room or enclosed floor space used or intended to be used for living, sleeping, cooking or eating

purposes, excluding bathrooms, laundries, furnace rooms, pantries, kitchenettes and utility rooms of less than

50 square feet of floor space, foyers, or communicating corridors, stairways, closets, storage spaces, workshops, and hobby

and recreation areas.

Health officer: the legally designated health authority of the jurisdiction or that person’s authorized representative.

Heated water: water heated to a temperature of not less than 120°F-130°F (49°C-54°C) at the outlet.

Heating device: all furnaces, unit heaters, domestic incinerators, cooking and heating stoves and ranges, and other similar devices.

Household: one or more individuals living together in a single dwelling unit and sharing common living, sleeping,

cooking, and eating facilities (see also Family).

Infestation: the presence within or around a dwelling of any insects, rodents, or other pests.

Integrated pest management: a coordinated approach to managing roaches, rodents, mosquitoes, and other pests that

combines inspection, monitoring, treatment, and evaluation, with special emphasis on the decreased use of toxic agents.

Kitchen: any room used for the storage and preparation of foods and containing the following equipment: sink or

other device for dishwashing, stove or other device for cooking, refrigerator or other device for cold storage of food,

cabinets or shelves for storage of equipment and utensils, and counter or table for food preparation.

Kitchenette: a small kitchen or an alcove containing cooking facilities.

Lead-based paint: any paint or coating with lead content equal to or greater than 1 milligram per square centimeter,

or 0.5% by weight.

Multiple dwelling: any dwelling containing more than two dwelling units.

Occupant: any individual, over 1 year of age, living, sleeping, cooking, or eating in or having possession of a dwelling

unit or a rooming unit; except that in dwelling units a guest shall not be considered an occupant.

Operator: any person who has charge, care, control or management of a building, or part thereof, in which dwelling

units or rooming units are let.

Ordinary summer conditions: a temperature 10°F (-12°C) below the highest recorded temperature in the locality for

the prior 10-year period.

Ordinary winter conditions: mean a temperature 15°F (-9.4°C) above the lowest recorded temperature in the locality

for the prior 10-year period.

Definitions

Owner: any person who alone, jointly, or severally with others (a) shall have legal title to any premises, dwelling, or

dwelling unit, with or without accompanying actual possession thereof, or (b) shall have charge, care or control of any

premises, dwelling, or dwelling unit, as owner or agent of the owner, or as executor, administrator, trustee, or guardian

of the estate of the owner.

Permissible occupancy: the maximum number of individuals permitted to reside in a dwelling unit, rooming unit, or dormitory.

Person: any individual, firm, corporation, association, partnership, cooperative, or government agency.

Plumbing: all of the following supplied facilities and equipment: gas pipes, gas burning equipment, water pipes,

garbage disposal units, waste pipes, toilets, sinks, installed dishwashers, bathtubs, shower baths, installed clothes

washing machines, catch basins, drains, vents, and similarly supplied fixtures, and the installation thereof, together with all

connections to water, sewer, or gas lines.

Privacy: the existence of conditions which will permit an individual or individuals to carry out an activity commenced

without interruption or interference, either by sight or sound by unwanted individuals.

Rat harborage: any conditions or place where rats can live, nest or seek shelter.

Ratproofing: a form of construction that will prevent the entry or exit of rats to or from a given space or building, or

from gaining access to food, water, or harborage. It consists of the closing and keeping closed of every opening in

foundations, basements, cellars, exterior and interior walls, ground or first floors, roofs, sidewalk gratings, sidewalk

openings, and other places that may be reached and entered by rats by climbing, burrowing, or other methods, by the

use of materials impervious to rat gnawing and other methods approved by the appropriate authority.

Refuse: leftover and discarded organic and nonorganic solids (except body wastes), including garbage, rubbish, ashes, and dead animals.

Refuse container: a watertight container that is constructed of metal, or other durable material impervious to rodents,

that is capable of being serviced without creating unsanitary conditions, or such other containers as have been

approved by the appropriate authority (see also Appropriate Authority). Openings into the container, such as covers and

doors, shall be tight fitting.

Rooming house: any dwelling other than a hotel or motel or that part of any dwelling containing one or more

rooming units, or one or more dormitory rooms, and in which persons either individually or as families are housed with or

without meals being provided.

Rooming unit: any room or group of rooms forming a single habitable unit used or intended to be used for living

and sleeping, but not for cooking purposes.

Rubbish: nonputrescible solid wastes (excluding ashes) consisting of either: (a) combustible wastes such as paper,

cardboard, plastic containers, yard clippings and wood; or (b) noncombustible wastes such as cans, glass, and crockery.

Safety: the condition of being reasonably free from danger and hazards that may cause accidents or disease.

Space heater: a self-contained heating appliance of either the convection type or the radiant type and intended

primarily to heat only a limited space or area such as one room or two adjoining rooms.

Supplied: paid for, furnished by, provided by, or under the control of the owner, operator or agent.

System: the dynamic interrelationship of components designed to enact a vision.

Healthy Housing Reference Manual

Standards and Organizations

In addition to the standards and organizations listed in this section, the U.S. Justice Department enforces the

requirements of the Americans with Disabilities Act (ADA) (http://www.ada.gov) and assures that products fully

comply with the provisions of the act to ensure equal access for physically challenged users.

ABPA

The American Backflow Prevention Association, http://abpa.org

Develops cross-connections; ABPA is an organization whose members have a common interest in

protecting drinking water from contamination.

ACI

American Concrete Institute, http://www.concrete.org/general/home.asp

Has produced more than 400 technical documents, reports, guides, specifications, and codes for the best use of

concrete. ACI conducts more than 125 educational seminars each year and has 13 certification programs

for concrete practitioners, as well as a scholarship program to promote careers in the industry.

AGA

American Gas Association, http://www.aga.org

Develops standards, tests, and qualifies products used in gas lines and gas appliance installations.

AGC

Associated General Contractors of America, http://www.agc.org

Is dedicated to improving the construction industry by educating the industry to employ the finest skills,

promoting use of the latest technology and advocating building the best quality projects for owners—

public and private.

AMSA

Association of Metropolitan Sewerage Agencies, http://www.amsa-cleanwater.org

Represents the interests of the country’s wastewater treatment agencies.

ANSI

American National Standards Institute, http://www.ansi.org

Coordinates work among U.S. standards writing groups. Works in conjunction with other groups such as

ISO, ASME, and ASTM.

ARI

Air-Conditioning and Refrigeration Institute, http://www.ari.org

Provides information about the 21st Century Research (21-CR) initiative, a private-public sector research

collaboration of the heating, ventilation, air-conditioning, and refrigeration industry, with a focus on

energy conservation, indoor environmental quality, and environmental protection.

ASCE

American Society of Civil Engineers, http://www.asce.org

Provides essential value to its members, careers, partners, and the public by developing leadership,

advancing technology, advocating lifelong learning, and promoting the profession.

ASHI

The American Society of Home Inspectors, http://www.ashi.org

Is a source of information about the home inspection profession.

ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers, http://www.ashrae.org

Writes standards and guidelines that include uniform methods of testing for rating purposes, describe

recommended practices in designing and installing equipment and provide other information to guide the

industry. ASHRAE has more than 80 active standards and guideline project committees, addressing such

broad areas as indoor air quality, thermal comfort, energy conservation in buildings, reducing refrigerant

emissions, and the designation and safety classification of refrigerants.

Healthy Housing Reference Manual

ASME

The American Society of Mechanical Engineers, http://www.asme.org

Develops standards for materials and testing as well as finished products.

ASSE

American Society of Sanitary Engineering, http://www.asse.org

Develops standards and qualifies products for plumbing and sanitary installations.

ASTM

American Society for Testing and Materials, http://www.astm.org

Is one of the largest voluntary standards development organizations in the world-a trusted source for

technical standards for materials, products, systems, and services.

AWWA

American Water Works Association, http://www.awwa.org

Promotes public health through improvement of the quality of water and develops standards for valves, fittings, and other

equipment.

CGA

Canadian Gas Association, http://www.cga.ca

Develops standards, tests, and qualifies products used in gas lines and gas appliance installations.

CPSC

U.S Consumer Product Safety Commission, http://www.cpsc.gov

Protects the public from unreasonable risks for serious injury or death from more than 15,000 types of

consumer products. CPSC is committed to protecting consumers and families from products that pose a

fire, electrical, chemical, or mechanical hazard or can injure children.

CRBT

Center for Resourceful Building Technology, http://www.crbt.org

Contains the online Guide to Resource-Efficient Building Elements, which provides information about

environmentally efficient construction materials, including foundations, wall systems, panels, insulation,

siding, roofing, doors, windows, interior finishing, and floor coverings.

EPA

U.S. Environmental Protection Agency, http://www.epa.gov

Protects human health and the environment.

Factory Mutual, http://fmglobal.com

Develops standards and qualifies products for use by the general public and develops standards for materials,

products, systems, and services.

HFHI

Habitat for Humanity International, http://www.habitat.org

Is a nonprofit, ecumenical Christian housing ministry. HFHI seeks to eliminate poverty housing and

homelessness from the world, and to make decent shelter a matter of conscience and action.

HUD

U.S. Department of Housing and Urban Development, http://www.hud.gov

As part of the HUD efforts toward eliminating childhood lead poisoning, the Office of Healthy Homes

and Lead Hazard Control is sharing local lead ordinances and regulations that have proven effective in

helping communities deal with lead-based paint hazards. Also, the design and construction of

manufactured housing are regulated by the federal government and must comply with HUD’s

Manufactured Home Construction and Safety Standards. Modular and panelized construction must

comply with model or local building codes.

IAPMO

International Association of Plumbing and Mechanical Officials, http://www.iapmo.org

Developed and maintains the Uniform Plumbing Code and the Uniform Mechanical Code.

Standards and Organizations

ICBO

The Uniform Building Code (UBC)/International Conference of Building Officials,

http://www.iccsafe.org

Is the most widely adopted model building code in the world and is a proven document meeting the

needs of government units charged with enforcement of building regulation. Published triennially, the

UBC provides complete regulations covering all major aspects of building design and construction relating

to fire and life safety and structural safety. The requirements reflect the latest technologic advances available

in the building and fire- and life-safety industry.

ICC

International Code Council, http://www.iccsafe.org

Produces the most widely adopted and enforced building safety codes in the United States (I-Codes).

International Residential Code (IRC) 2003 has been adopted by many states, jurisdictions, and localities.

IRC also references several industry standards such as ACI 318, ASCE 7, ASTM, and ANSI standards that

cover specific load, load combinations, design methods, and material specifications.

ISO

International Standard Organization, http://www.iso.org

Provides internationally recognized certification for manufacturers that comply with high standards of

quality control, developed standards ISO-9000 through ISO-9004, and qualifies and lists products suitable for

use in plumbing installations.

MSS

Manufacturers Standardization Society of the Valve and Fittings Industry, Inc., http://www.mss-hq.com

Develops technical codes and standards for the valve and fitting industry.

NACHI

The National Association of Certified Home Inspectors, http://www.nachi.org/index.htm

Is the world’s largest, most elite nonprofit inspection association.

NAHB

National Association of Home Builders, http://www.nahb.org

Is a trade association representing more than 220,000 residential home building and remodeling industry

members. NAHB is affiliated with more than 800 state and local home builders associations around the

country. NAHB urges codes and standards development and application that protects public health and

safety without cost impacts that decrease affordability and consequently prevent people from moving into

new, healthier, safer homes.

NEC

National Electrical Code, http://www.nfpa.org

Protects public safety by establishing requirements for electrical wiring and equipment in virtually all

buildings.

NESC

National Environmental Services Center, http://www.nesc.wvu.edu/nesc/nesc_about.htm

Is a repository for water, wastewater, solid waste, and environmental training research.

NFPA

National Fire Protection Association, http://www.nfpa.org/index.asp

Develops, publishes, and disseminates more than 300 consensus codes and standards intended to

minimize the possibility and effects of fire and other risks.

NOWRA

National Onsite Wastewater Recycling Association, http://www.nowra.org

Provides leadership and promotes the onsite wastewater treatment and recycling industry through

education, training, communication, and quality tools to support excellence in performance.

NSF

National Sanitation Foundation, http://www.nsf.org

Develops standards for equipment, products and services; a nonprofit organization now known as NSF

International.

Healthy Housing Reference Manual

Executive Summary

he original Basic Housing Inspection manual was published in 1976 by the Center for Disease Control (now

known as the Centers for Disease Control and Prevention). Its Foreword stated:

“The growing numbers of new families and the increasing population in the United States have

created a pressing demand for additional housing that is conducive to healthful living. These

demands are increased by the continuing loss of existing housing through deterioration resulting

from age and poor maintenance. Large numbers of communities in the past few years have adopted

housing codes and initiated code enforcement programs to prevent further deterioration of existing

housing units. This growth in housing activities has caused a serious problem for communities in

obtaining qualified personnel to provide the array of housing service needed, such as information,

counseling, technical advice, inspections, and enforcement. As a result many agencies throughout the

country are conducting comprehensive housing inspection training courses. This publication has

been designed to be an integral part of these training sessions.”

The original Basic Housing Inspection manual has been successfully used for several decades by public health and

housing personnel across the United States. Although much has changed in the field of housing construction and

maintenance, and health and safety issues have expanded, the manual continues to have value, especially as it relates to

older housing.

Many housing deficiencies impact on health and safety. For example, lead-based paint and dust may contribute to

lead poisoning in children; water leakage and mold may contribute to asthma episodes; improper use and storage of

pesticides may result in unintentional poisoning; and lack of working smoke, ionization, and carbon monoxide alarms may

cause serious injury and death.

Government agencies have been very responsive to “healthy homes” issues. The U.S. Department of Housing and

Urban Development (HUD) created an office with an exclusive focus on healthy homes. In 2003, CDC joined HUD

in the effort to improve housing conditions through the training of environmental health practitioners, public health

nurses, housing specialists, and others who have interest and responsibility for creating healthy homes.

The revised Basic Housing Inspection manual, renamed the Healthy Housing Reference Manual, responds to the

enormous changes that have occurred in housing construction methods and materials and to new knowledge related

to the impact of housing on health and safety. New chapters have been added, making the manual more

comprehensive. For example, an entire chapter is devoted to rural water supplies and on-site wastewater treatment. A

new chapter was added that discusses issues related to residential swimming pools and spas. At over 230 pages, the

comprehensive revised manual is designed primarily as a reference document for public health and housing

professionals who work in government and industry.

The Healthy Housing Reference Manual contains 14 chapters, each with a specific focus. All chapters contain annotated

references and a listing of sources for additional topic information. A summary of the content of each chapter follows:

Chapter One, Housing History and Purpose, describes the history of dwellings and urbanization and housing

trends during the last century.

Chapter Two, Basic Principles of Healthy Housing, describes the basic principles of healthy housing and

safety—physiologic needs, psychologic needs, protection against injury and disease—and lays the groundwork

for following chapters.

Healthy Housing Reference Manual

Chapter Three, Housing Regulations, reviews the history of housing regulations, followed by a discussion of

zoning, housing, and building codes.

Chapter Four, Disease Vectors and Pests, provides a detailed analysis of disease vectors that have an impact on

residences. It includes information on the management of mice, rats, cockroaches, fleas, flies, termites, and fire ants.

Chapter Five, Indoor Air Pollution and Toxic Materials, provides information on indoor air pollution, both

biologic and chemical, and to toxic materials in the home, including methods for controlling these hazards. The

impact of cockroaches, dust mites, pets, and mold are discussed. Also included is information about the impact

of carbon monoxide, ozone, tobacco smoke, volatile organic compounds, radon, and pesticides.

Chapter Six, Housing Structure, contains information about “older” housing construction and new construction

materials and methods. The chapter also introduces new terminologies and includes information about

foundations, vapor barriers, house framing, roof framing, exterior walls, and roofs.

Chapter Seven, Environmental Barriers, provides information on roofing, insulation, and siding materials.

Chapter Eight, Rural Water Supplies and Water-quality Issues, covers issues related to the drilling and proper

maintenance of wells. Research information is provided that indicates that many wells are not properly sealed,

allowing for the leakage of contaminated water into wells during hurricanes and periods of significant flooding.

Chapter Nine, Plumbing, provides information on plumbing standards and how they can be accessed, followed

by a review of the elements of a residential water delivery system, the types of available hot-water heaters,

drainage systems, and methods for water conservation. It also includes a visual synthesis of water system

components during new residential construction.

Chapter Ten, On-site Wastewater Treatment, complements chapter seven by providing information on proper

on-site methods for the treatment of human waste.

Chapter Eleven, Electricity, expands on information contained in the original manual covering such topics as

breaker systems and polarized plugs and connectors. It also provides a format for the inspection of residential

electrical systems.

Chapter Twelve, Heating, Air Conditioning, and Ventilation, provides information about types of residential

fuels and heating systems, including solar heating and minor sources of heating (e.g., coal-fired, oil-fired, gas-

fired, and electrical space heaters). Chimney and fireplace safety and the variety of cooling systems are also

discussed.

Chapter Thirteen, Energy Efficiency, discusses energy efficiency, including R-values and their interpretation, roof

ventilation, wall and floor insulation, and door and window energy efficiency systems. It also discusses active and

passive solar systems and provides a methodology for conducting a residential energy audit.

Chapter Fourteen, Residential Swimming Pools and Spas, provides information about child safety, pool and spa

hazards, and diseases. It also provides information on methods for testing and ensuring a safe water system and

on methods for spa and pool disinfection. Further, it covers concerns related to unregulated individual

residential pools and spas.

Executive Summary

The quality of housing plays a decisive role in the health status of its occupants. Substandard housing conditions have

been linked to adverse health effects such as childhood lead poisoning, asthma and other respiratory conditions, and

unintentional injuries. This new and revised Healthy Housing Reference Manual is an important reference for anyone

with responsibility and interest in creating and maintaining healthy housing.

The housing design and construction industry has made great progress in recent years through the development of

new innovative techniques, materials technologies, and products. The HUD Rehab Guide series was developed to

inform the design and construction industry about state-of-the-art materials and innovative practices in housing

rehabilitation. The series focuses on building technologies, materials, components, and techniques rather than on

projects such as adding a new room. The nine volumes each cover a distinct element of housing rehabilitation and

feature breakthrough materials, labor-saving tools, and cost-cutting practices. The nine volumes address foundations;

exterior walls; roofs; windows and doors; partitions, ceilings, floors, and stairs; kitchen and baths; electrical/

electronics; heating, air conditioning, and ventilation; plumbing; and site work.

Additional information about the series can be found at http://www.huduser.org/publications/destech/rehabgui.html

and http://www.pathnet.org/sp.asp?id=997. This series is an excellent adjunct to the Healthy Housing Reference Manual.

Healthy Housing Reference Manual

Chapter 1: Housing History and Purpose

“Safe, affordable housing is a basic necessity for every family.

code inspectors, housing inspectors, environmental health

Without a decent place to live, people cannot be productive

officers, injury control specialists, and epidemiologists all

members of society, children cannot learn and families

are indispensable to achieving the goal of the best

cannot thrive.”

housing in the world for U.S. citizens. This goal is the

basis for the collaboration of the U.S. Department of

Tracy Kaufman, Research Associate

Housing and Urban Development (HUD) and the

National Low Income Housing Coalition/

Centers for Disease and Control and Prevention (CDC).

Low Income Housing Information Service

http://www.habitat.org/how/poverty.html; 2003

Preurban Housing

Early dwelling designs were probably the result of cultural,

Introduction

socioeconomic, and physical forces intrinsic to the

The term “shelter,” which is often used to define housing,

environment of their inhabitants. The housing similarities

has a strong connection to the ultimate purpose of

among civilizations separated by vast distances may have

housing throughout the world. The mental image of a

been a result of a shared heritage, common influences,

shelter is of a safe, secure place that provides both privacy

or chance.

and protection from the elements and the temperature

extremes of the outside world.

Caves were accepted as dwellings, perhaps because they

were ready made and required little or no construction.

This vision of shelter, however, is complex. The

However, in areas with no caves, simple shelters were

earthquake in Bam, Iran, before dawn on December 26,

constructed and adapted to the availability of resources

2003, killed in excess of 30,000 people, most of whom

and the needs of the population. Classification systems

were sleeping in their homes. Although the homes were

have been developed to demonstrate how dwelling types

made of the most simple construction materials, many

evolved in preurban indigenous settings [1].

were well over a thousand years old. Living in a home

where generation after generation had been raised should

Ephemeral Dwellings

provide an enormous sense of security. Nevertheless, the

Ephemeral dwellings, also known as transient dwellings,

world press has repeatedly implied that the construction

were typical of nomadic peoples. The African bushmen

of these homes destined this disaster. The homes in Iran

and Australia’s aborigines are examples of societies whose

were constructed of sun-dried mud-brick and mud.

existence depends on an economy of hunting and food

gathering in its simple form. Habitation of an ephemeral

We should think of our homes as a legacy to future

dwelling is generally a matter of days.

generations and consider the negative environmental

effects of building them to serve only one or two

Episodic Dwellings

generations before razing or reconstructing them. Homes

Episodic housing is exemplified by the Inuit igloo, the

should be built for sustainability and for ease in future

tents of the Tungus of eastern Siberia, and the very

modification. We need to learn the lessons of the

similar tents of the Lapps of northern Europe. These

earthquake in Iran, as well as the 2003 heat wave in

groups are more sophisticated than those living in

France that killed in excess of 15,000 people because of

ephemeral dwellings, tend to be more skilled in hunting

the lack of climate control systems in their homes. We

or fishing, inhabit a dwelling for a period of weeks, and

must use our experience, history, and knowledge of both

have a greater effect on the environment. These groups

engineering and human health needs to construct

also construct communal housing and often practice

housing that meets the need for privacy, comfort,

slash-and-burn cultivation, which is the least productive

recreation, and health maintenance.

use of cropland and has a greater environmental impact

than the hunting and gathering of ephemeral dwellers.

Health, home construction, and home maintenance are

inseparable because of their overlapping goals. Many

Periodic Dwellings

highly trained individuals must work together to achieve

Periodic dwellings are also defined as regular temporary

quality, safe, and healthy housing. Contractors, builders,

dwellings used by nomadic tribal societies living in a

Healthy Housing Reference Manual

1-1

pastoral economy. This type of housing is reflected in the

Urbanization

yurt used by the Mongolian and Kirgizian groups and the

Permanent dwellings went beyond simply providing

Bedouins of North Africa and western Asia. These groups’

shelter and protection and moved to the consideration of

dwellings essentially demonstrate the next step in the

comfort. These structures began to find their way into what is

evolution of housing, which is linked to societal

now known as the urban setting. The earliest available

development. Pastoral nomads are distinguished from

evidence suggests that towns came into existence around

people living in episodic dwellings by their homogenous

4000 BC. Thus began the social and public health problems

cultures and the beginnings of political organization.

that would increase as the population of cities increased

Their environmental impact increases with their increased

in number and in sophistication. In preurban housing,

dependence on agriculture rather than livestock.

the sparse concentration of people allowed for movement

away from human pollution or allowed the dilution of

Seasonal Dwellings

pollution at its location. The movement of populations

Schoenauer [1] describes seasonal dwellings as reflective of

into urban settings placed individuals in close proximity,

societies that are tribal in nature, seminomadic, and based

without the benefit of previous linkages and without the

on agricultural pursuits that are both pastoral and

ability to relocate away from pollution or other people.

marginal. Housing used by seminomads for several

months or for a season can be considered semisedentary

Urbanization was relatively slow to begin, but once

and reflective of the advancement of the concept of

started, it accelerated rapidly. In the 1800s, only about

property, which is lacking in the preceding societies. This

3% of the population of the world could be found in

concept of property is primarily of communal property, as

urban settings in excess of 5,000 people. This was soon to

opposed to individual or personal property. This type of

change. The year 1900 saw the percentage increase to

housing is found in diverse environmental conditions and is

13.6% and subsequently to 29.8% in 1950. The world’s

demonstrated in North America by the hogans and armadas

urban population has grown since that time. By 1975,

of the Navajo Indians. Similar housing can be found in

more than one in three of the world’s population lived in

Tanzania (Barabaig) and in Kenya and Tanzania (Masai).

an urban setting, with almost one out of every two living

in urban areas by 1997. Industrialized countries currently

Semipermanent Dwellings

find approximately 75% of their population in an urban

According to Schoenauer [1], sedentary folk societies or

setting. The United Nations projects that in 2015 the

hoe peasants practicing subsistence agriculture by

world’s urban population will rise to approximately 55%

cultivating staple crops use semipermanent dwellings.

and that in industrialized nations it will rise to just over 80%.

These groups tend to live in their dwellings various amounts

of time, usually years, as defined by their crop yields. When

In the Western world, one of the primary forces driving

land needs to lie fallow, they move to more fertile areas.

urbanization was the Industrial Revolution. The basic

Groups in the Americas that used semipermanent

source of energy in the earliest phase of the Industrial

dwellings included the Mayans with their oval houses and

Revolution was water provided by flowing rivers. Therefore,

the Hopi, Zuni, and Acoma Indians in the southwestern

towns and cities grew next to the great waterways. Factory

United States with their pueblos.

buildings were of wood and stone and matched the houses

in which the workers lived, both in construction and in

Permanent Dwellings

location. Workers’ homes were little different in the urban

The homes of sedentary agricultural societies, whose

setting than the agricultural homes from whence they

political and social organizations are defined as nations

came. However, living close to the workplace was a

and who possess surplus agricultural products, exemplify

definite advantage for the worker of the time. When the

this type of dwelling. Surplus agricultural products

power source for factories changed from water to coal,

allowed the division of labor and the introduction of

steam became the driver and the construction materials

other pursuits aside from food production; however,

became brick and cast iron, which later evolved into

agriculture is still the primary occupation for a significant

steel. Increasing populations in cities and towns increased

portion of the population. Although they occurred at

social problems in overcrowded slums. The lack of

different points in time, examples of early sedentary

inexpensive, rapid public transportation forced many

agricultural housing can be found in English cottages,

workers to live close to their work. These factory areas

such as the Suffolk, Cornwall, and Kent cottages [1].

were not the pastoral areas with which many were

familiar, but were bleak with smoke and other pollutants.

The inhabitants of rural areas migrated to ever-expanding

1-2

Housing History and Purpose

cities looking for work. Between 1861 and 1911 the

population of England grew by 80%. The cities and

towns of England were woefully unprepared to cope with

the resulting environmental problems, such as the lack of

potable water and insufficient sewerage.

In this atmosphere, cholera was rampant; and death rates

resembled those of Third World countries today. Children

had a one in six chance of dying before the age of 1 year.

Because of urban housing problems, social reformers such

as Edwin Chadwick began to appear. Chadwick’s Report

on an Enquiry into the Sanitary Condition of the Labouring

Population of Great Britain and on the Means of its

Improvement [2] sought many reforms, some of which

concerned building ventilation and open spaces around

the buildings. However, Chadwick’s primary contention

was that the health of the working classes could be improved

by proper street cleaning, drainage, sewage, ventilation,

and water supplies. In the United States, Shattuck et al.

[3] wrote the Report of the Sanitary Commission of

Massachusetts, which was printed in 1850. In the report,

50 recommendations were made. Among those related to

housing and building issues were recommendations for

protecting school children by ventilation and sanitation of

school buildings, emphasizing town planning and controlling

Figure 1.1. Conditions in the Tenements

overcrowded tenements and cellar dwellings. Figure 1.1

demonstrates the conditions common in the tenements.

1830s as a housing unit of two to five stories, with each

story containing apartments of two to four rooms. It was

In 1845, Dr. John H. Griscom, the City Inspector of

originally built for the upper group of the working class.

New York, published The Sanitary Condition of the

The tenement house emerged in the 1830s when

Laboring Population of New York [4]. His document

landlords converted warehouses into inexpensive housing

expressed once again the argument for housing reform

designed to accommodate Irish and black workers.

and sanitation. Griscom is credited with being the first to

Additionally, existing large homes were subdivided and

use the phrase “how the other half lives.” During this

new structures were added, creating rear houses and, in

time, the poor were not only subjected to the physical

the process, eliminating the traditional gardens and yards

problems of poor housing, but also were victimized by

behind them. These rear houses, although new, were

corrupt landlords and builders.

no healthier than the front house, often housing up to

10 families. When this strategy became inadequate to

Trends in Housing

satisfy demand, the epoch period of the tenements began.

The term “tenement house” was first used in America and

dates from the mid-nineteenth century. It was often

Although unpopular, the tenement house grew in

intertwined with the term “slum.” Wright [5] notes that

numbers, and, by 1850 in New York and Boston, each

in English, tenement meant “an abode for a person or for

tenement housed an average of 65 people. During the

the soul, when someone else owned the property.” Slum,

1850s, the railroad house or railroad tenement was

on the other hand, initially was used at the beginning of

introduced. This structure was a solid, rectangular block

the 19th century as a slang term for a room. By the

with a narrow alley in the back. The structure was

middle of the century, slum had evolved into a term for a

typically 90 feet long and had 12 to 16 rooms, each about

back dwelling occupied by the lowest members of society.

6 feet by 6 feet and holding around four people. The

Von Hoffman [6] states that this term had, by the end of

facility allowed no direct light or air into rooms except

the century, begun to be used interchangeably with

those facing the street or alley. Further complicating this

tenement. The author noted that in the larger cities of

structure was the lack of privacy for the tenants. A lack of

the United States, the apartment house emerged in the

hallways eliminated any semblance of privacy. Open sewers,

a single privy in the back of the building, and uncollected

Healthy Housing Reference Manual

1-3

garbage resulted in an objectionable and unhygienic place to

bungalow was introduced into the United States in 1880

live. Additionally, the wood construction common at the

with the construction of a home in Cape Cod. The bungalow,

time, coupled with coal and wood heating, made fire an

derived for use in tropical climates, was especially popular

ever-present danger. As a result of a series of tenement

in California.

fires in 1860 in New York, such terms as death-trap and

fire-trap were coined to describe the poorly constructed

Company towns were another trend in housing in the

living facilities [6].

19th century. George Pullman, who built railway cars in the

1880s, and John H. Patterson, of the National Cash

The two last decades of the 19th century saw the

introduction and development of dumbbell tenements, a

Wright [5] notes that in 1917 the U.S. Bureau of Labor

front and rear tenement connected by a long hall. These

Standards estimated that at least 1,000 industrial firms were

tenements were typically five stories, with a basement and

providing housing for their employees. The provision of

no elevator (elevators were not required for any building

housing was not necessarily altruistic. The motivation

of less than six stories). Dumbbell tenements, like other

for providing housing varied from company to company.

tenements, resulted in unaesthetic and unhealthy places to

Such motivations included the use of housing as a

live. Garbage was often thrown down the airshafts, natural

recruitment incentive for skilled workers, a method of

light was confined to the first floor hallway, and the public

linking the individual to the company, and a belief that a

hallways only contained one or two toilets and a sink.

better home life would make the employees happier and

This apparent lack of sanitary facilities was compounded

more productive in their jobs. Some companies, such as

by the fact that many families took in boarders to help with

Firestone and Goodyear, went beyond the company town

expenses. In fact, 44,000 families rented space to boarders

and allowed their employees to obtain loans for homes

in New York in 1890, with this increasing to 164,000

from company-established banks. A prime motivator of

families in 1910. In the early 1890s, New York had a

company town planning was sanitation, because

population of more than 1 million, of which 70% were

maintaining the worker’s health could potentially lead to

residents of multifamily dwellings. Of this group, 80%

fewer workdays lost due to illness. Thus, in the

lived in tenements consisting mostly of dumbbell tenements.

development of the town, significant consideration was

given to sanitary issues such as window screens, sewage

The passage of the New York Tenement House Act of

treatment, drainage, and water supplies.

1901 spelled the end of the dumbbells and acceptance of

a new tenement type developed in the 1890s—the park

Before World War I there was a shortage of adequate

or central court tenement, which was distinguished by a

dwellings. Even after World War I, insufficient funding, a

park or open space in the middle of a group of buildings.

shortage of skilled labor, and a dearth of building materials

This design was implemented to reduce the activity on

compounded the problem. However, the design of homes

the front street and to enhance the opportunity for fresh

after the war was driven in part by health considerations,

air and recreation in the courtyard. The design often

such as providing good ventilation, sun orientation and

included roof playgrounds, kindergartens, communal

exposure, potable pressurized water, and at least one

laundries, and stairways on the courtyard side.

private toilet. Schoenauer [1] notes that, during the

postwar years, the improved mobility of the public led to

Although the tenements did not go away, reform groups

an increase in the growth of suburban areas, exemplified

supported ideas such as suburban cottages to be

by the detached and sumptuous communities outside

developed for the working class. These cottages were two-

New York, such as Oyster Bay. In the meantime, the

story brick and timber, with a porch and a gabled roof.

conditions of working populations consisting of many

According to Wright [5], a Brooklyn project called

immigrants began to improve with the improving

Homewood consisted of 53 acres of homes in a planned

economy of the 1920s. The garden apartment became

neighborhood from which multifamily dwellings, saloons,

popular. These units were well lighted and ventilated and

and factories were banned.

had a courtyard, which was open to all and well maintained.

Although there were many large homes for the well-to-do,

Immediately after World War I and during the 1920s, city

single homes for the not-so-wealthy were not abundant.

population growth was outpaced by population growth in

The first small house designed for the individual of

the suburbs by a factor of two. The focus at the time was

modest means was the bungalow. According to

on the single-family suburban dwelling. The 1920s were a

Schoenauer [1], bungalows originated in India. The

time of growth, but the decade following the Great

1-4

Housing History and Purpose

History of the Department of Housing and Urban Development

1934

Housing Act establishes Federal Housing Administration to insure mortgages and make loans to

low-income families; Fannie Mae created.

1937

Housing Act establishes public housing.

1944

Serviceman’s Readjustment Act creates Veteran Administration mortgages; trend toward

suburbia begins.

Late 1950s

Urban renewal begins; slum clearance developed to promote construction of affordable housing.

1965

Department of Housing and Urban Development created.

1968

Model Cities program launched; fair housing launched through the Civil Rights Act.

1971

Lead-Based Paint Poisoning Prevention Act passed.

1974

Section 8 rental subsidy program begins; Community Development Block Grant program begins.

1977

Urban Development Action Grants begin.

1986

Low-income housing tax credit created.

1987

McKinney Homeless Assistance Act passed; creation of low-income housing tax credit.

1991-1994

Public housing inspection for lead paint.

1992

Residential Lead Hazard Reduction Act passed (Title X of the 1992 Housing and Community

Development Act).

1993

Hope VI program begins to redevelop old public housing.

1996

Lead-based paint disclosure becomes law.

1999

HUD and CDC launch the Healthy Homes Initiative.

2000

HUD publishes new lead paint regulations for federally funded assisted housing; President’s Task

Force releases federal interagency plan to eliminate childhood lead paint poisoning by 2010.

2001

EPA publishes final standards for lead in paint, dust, and soil in housing.

Depression, beginning in 1929, was one of deflation,

and loan associations, and others to make loans for

cessation of building, loss of mortgage financing, and the

building homes, small business establishments, and farm

plunge into unemployment of large numbers of building

buildings. If the Federal Housing Administration

trade workers. Additionally, 1.5 million home loans were

approved the plans, it would insure the loan. In 1937,

foreclosed during this period. In 1936, the housing market

Congress passed another National Housing Act that

began to make a comeback; however, the 1930s would

enabled the Federal Housing Administration to take

come to be known as the beginning of public housing,

control of slum clearance. It made 60-year loans at low

with increased public involvement in housing

interest to local governments to help them build

construction, as demonstrated by the many laws passed

apartment blocks. Rents in these homes were fixed and

during the era [5]. The National Housing Act was

were only available to low-income families. By 1941, the

passed by Congress in 1934 and set up the Federal Housing

agency had assisted in the construction of more than

Administration. This agency encouraged banks, building

120,000 family units.

Healthy Housing Reference Manual

1-5

During World War II, the focus of home building was on

Builders also began promoting one-floor minihomes and

housing for workers who were involved in the war effort.

no-frills homes of approximately 900 to 1,200 square feet.

Homes were being built through federal agencies such as

Manufactured housing began to increase in popularity,

the newly formed Federal Housing Administration, formed

with mobile home manufacturers becoming some of the

in 1934 and transferred to HUD in 1965. According to

most profitable corporations in the United States in the

the U.S. Census Bureau (USCB) [7], in the years since

early 1970s. In the 1940 census, manufactured housing

World War II, the types of homes Americans live in have

were lumped into the “other” category with boats and tourist

changed dramatically. In 1940, most homes were considered

cabins: by the 1990 census, manufactured housing made up

attached houses (row houses, townhouses, and duplexes).

7% of the total housing inventory. Many communities

Small apartment houses with two to four apartments had

ban manufactured housing from residential

their zenith in the 1950s. In the 1960 census, two-thirds

neighborhoods.

of the housing inventory was made up of one-family detached

houses, which declined to less than 60% in the 1990 census.

According to Hart et al. [9], nearly 30% of all home sales

nationwide are of manufactured housing, and more than

The postwar years saw the expansion of suburban housing

90% of those homes are never moved once they are

led by William J. Levitt’s Levittown, on Long Island,

anchored. According to a 2001 industry report, the

which had a strong influence on postwar building and

demand for prefabricated housing is expected to increase

initiated the subdivisions and tract houses of the

in excess of 3% annually to $20 billion in 2005, with

following decades (Figure 1.2). The 1950s and 1960s saw

most units being manufactured homes. The largest

continued suburban development, with the growing ease of

market is expected to continue in the southern part of the

transportation marked by the expansion of the interstate

United States, with the most rapid growth occurring in

highway system. As the cost of housing began to increase

the western part of the country. As of 2000, five

as a result of increased demand, a grassroots movement to

manufactured-home producers, representing 35% of the

provide adequate housing for the poor began to emerge.

market, dominated the industry. This industry, over the

According to Wright [5], in the 1970s only about 25% of the

past 20 to 25 years, has been affected by two pieces of

population could afford a $35,000 home. According to

federal legislation. The first, the Mobile Home

Gaillard [8], Koinonia Partners, a religious organization

Construction and Safety Standards Act, adopted by HUD

founded in 1942 by Clarence Jordan near Albany,

in 1974, was passed to aid consumers through regulation

Georgia, was the seed for Habitat for Humanity. Habitat

and enforcement of HUD design and construction

for Humanity, founded in 1976 by Millard Fuller, is

standards for manufactured homes. The second, the 1980

known for its international efforts and has constructed

Housing Act, required the federal government to change

more than 150,000 houses in 80 countries; 50,000 of these

the term “mobile home” to “manufactured housing” in all

houses are in the United States. The homes are energy-

federal laws and literature. One of the prime reasons for

efficient and environmentally friendly to conserve resources

this change was that these homes were in reality no longer

and reduce long-term costs to the homeowners.

mobile in the true sense.

The energy crisis in the United States between 1973 and

1974 had a major effect on the way Americans lived,

drove, and built their homes. The high cost of both

heating and cooling homes required action, and some of

the action taken was ill advised or failed to consider

healthy housin concerns. Sealing homes and using untried

insulation materials and other energy conservation actions

often resulted in major and sometimes dangerous

buildups of indoor air pollutants. These buildups of

toxins occurred both in homes and offices. Sealing

buildings for energy efficiency and using off-gassing

building materials containing urea-formaldehyde, vinyl,

and other new plastic surfaces, new glues, and even

wallpapers created toxic environments. These newly sealed

environments were not refreshed with makeup air and

Figure 1.2. Levittown, New York

resulted in the accumulation of both chemical and

1-6

Housing History and Purpose

biologic pollutants and moisture leading to mold growth,

Hale EE. Workingmen’s homes, essays and stories, on the

representing new threats to both short-term and long-

homes of men who work in large towns. Boston: James

term health. The results of these actions are still being

R. Osgood and Company; 1874.

dealt with today.

History of plumbing in America. Plumbing and

References

Mechanical Magazine. 1987 Jul. Available from URL:

Schoenauer N. 6,000 years of housing. New York/

http://www.plumbingsupply.com/pmamerica.html.

London: W.W. Norton & Company, Inc.; 2000.

Housing Act of 1949, The US Committee on

Chadwick E. Report on an enquiry into the

Agriculture Glossary.

sanitary condition of the labouring population of

Great Britain and on the means of its

Lang RE, Sohmer RR. Editors’ introduction, legacy of

improvements. London: Clowes and Sons; 1842.

the Housing Act of 1949: the past, present, and future of

federal housing and urban policy. Housing Policy Debate

Shattuck L, Banks N Jr, Abbot J. Report of the

2000; 11(2) 291-8. Available from URL:

Sanitary Commission of Massachusetts, 1850.

http://www.fanniemaefoundation.org/ programs/hpd/v11i2-

Boston: Dutton and Wentworth; 1850. Available

edintro.shtml.

from URL: http://www.deltaomega.org/shattuck.pdf.

Mason JB. History of housing in the US. 1930-1980.

Griscom JH. The sanitary condition of the

Houston, TX: Gulf Publishing Company; 1982.

labouring population of New York. New York:

Harper; 1845.

Passic F. Urban renewal. Morning Star [Albion,

Michigan]. 1997 Feb 13; 6. Available from URL:

Wright G. Building the dream—a social history

http://www.albionmich.com/ history/

of housing in America. Cambridge, MA/London:

histor_notebook/940213.shtml.

The MIT Press; 1998.

Red-lining [definition of], 535A.1 Definitions, Iowa

Von Hoffman A. The origins of American

Code 2001: Section 535A.1. Des Moines, IA: The Iowa

housing reform. Cambridge, MA: Joint Center

Legislature. Available from URL:

for Housing Studies—Harvard University; August

http://www.legis.state.ia.us/IACODE/

1998. p. W98-2.

2001/535A/1.html.

US Census Bureau. Historical census of housing

Rental Housing On Line. Federal housing acts. Port

tables—units in structure; 2002. Washington, DC:

Huron, MI: Rental Housing On Line; no date. Available

US Census Bureau; 2002. Available from URL:

from URL: http://www.rhol.org/rental/fedact.htm.

http://www.census.gov/hhes/www/housing/census/

historic/units.html.

Rental Housing On Line. Government’s role in low

income housing. Port Huron, MI: Rental Housing

Gaillard F. If I were a carpenter, twenty years of

On Line; no date. Available from URL:

Habitat for Humanity. Winston-Salem, NC:

http://www.rhol.org/rental/housing.htm.

John E. Blair; 1996.

Texas Low Income Housing Information Service. The

Hart JF, Rhodes MJ, Morgan JT, Lindberg MB.

past: special interests, race, and local control; Housing

The unknown world of the mobile home.

Act of 1949: bipartisan support for public housing.

Baltimore, MD: Johns Hopkins University

Austin, TX: Texas Low Income Housing Information

Press; 2002.

Service; no date. Available from URL:

http://www.texashousing.org/txlihis/ phdebate/past12.html.

Additional Sources of Information

Dolkart A. The 1901 Tenement House Act: chapter 6,

US Department of Housing and Urban Development.

cleaning up the toilets. New York: Lower East Side

Fair housing laws and presidential Executive Orders.

Tenement Museum; no date. Available from URL:

Washington, DC: US Department of Housing and

http://www.tenement.org/ features_dolkart7.html.

Healthy Housing Reference Manual

1-7

Chapter 2: Basic Principles of Healthy Housing

“The connection between health and dwelling is one of the

6. direct sunlight,

most important that exists.”

7. adequate artificial illumination and avoidance of glare,

Florence Nightingale

8. protection from excessive noise, and

Introduction

It seems obvious that health is related to where people

9. adequate space for exercise and for children to play.

live. People spend 50% or more of every day inside their

homes. Consequently, it makes sense that the housing

The first three physiologic needs reflect the requirement

environment constitutes one of the major influences on

for adequate protection from the elements. The lack of

health and well-being. Many of the basic principles of the

adequate heating and cooling systems in homes can

link between housing and health were elucidated more

contribute to respiratory illnesses or even lead to death

than 60 years ago by the American Public Health

from extreme temperatures. According to the National

Association (APHA) Committee on the Hygiene of

Weather Service, 98 people died from extreme

Housing. After World War II, political scientists,

temperatures in 1996; 62 of these were due to extreme

sociologists, and others became interested in the relation

cold. Hypothermia occurs when the body temperature

between housing and health, mostly as an outgrowth of a

drops below 96°F (46°C). It can occur in any person

concern over poor housing conditions resulting from the

exposed to severe cold without enough protection. Older

massive influx into American cities of veterans looking

people are particularly susceptible because they may not

for jobs. Now, at the beginning of the 21st century, there is

notice the cold as easily and can develop hypothermia

a growing awareness that health is linked not only to the

even after exposure to mild cold. Susceptibility to the

physical structure of a housing unit, but also to the

cold can be exacerbated by certain medications, medical

neighborhood and community in which the house is located.

conditions, or the consumption of alcohol. Hyperthermia is

the name given to a variety of heat-related illnesses. The two

According to Ehlers and Steel [1], in 1938, a Committee

most common forms of hyperthermia are heat

on the Hygiene of Housing, appointed by APHA,

exhaustion and heat stroke. Of the two, heat stroke is

created the Basic Principles of Healthful Housing, which

especially dangerous and requires immediate medical attention.

provided guidance regarding the fundamental needs of

humans as they relate to housing. These fundamental

According to the National Institute on Aging (NIA) [2],

needs include physiologic and psychologic needs,

lifestyle factors can increase the risk for hyperthermia:

protection against disease, protection against injury,

protection against fire and electrical shock, and

Unbearably hot living quarters. This would include

protection against toxic and explosive gases.

people who live in homes without fans or air

conditioners. To help avert the problem, residents should

Fundamental Physiologic Needs

open windows at night; create cross-ventilation by opening

Housing should provide for the following physiologic needs:

windows on two sides of the building; cover windows

when they are exposed to direct sunlight and keep curtains,

1. protection from the elements,

shades, or blinds drawn during the hottest part of the day.

2. a thermal environment that will avoid undue heat loss,

Lack of transportation. People without fans or air conditioners

often are unable to go to shopping malls, movie theaters, and

3. a thermal environment that will permit adequate

libraries to cool off because of illness or the lack of

heat loss from the body,

transportation.

4. an atmosphere of reasonable chemical purity,

Inadequate or inoperable windows. Society has become

so reliant on climate control systems that when they fail,

5. adequate daylight illumination and avoidance

windows cannot be opened. As was the case in the 2003

of undue daylight glare,

heat wave in France, many homes worldwide do not even

have fans for cooling.

Healthy Housing Reference Manual

2-1

Overdressing. Older people, because they may not feel

formed a Noise Abatement Commission that was charged

the heat, may not dress appropriately in hot weather.

with evaluating noise issues and suggesting solutions. At

that time, it was concluded that loud noise affected health

Visiting overcrowded places. Trips should be scheduled

and productivity. In 1930, this same commission

during nonrush-hour times and participation in special events

determined that constant exposure to loud noises could

should be carefully planned to avoid disease transmission.

affect worker efficiency and long-term hearing levels. In

1974, the U.S. Environmental Protection Agency (EPA)

Not checking weather conditions. Older people,

produced a document titled Information on Levels of

particularly those at special risk, should stay indoors on

Environmental Noise Requisite to Protect Public Health and

especially hot and humid days, particularly when an air

Welfare With an Adequate Margin of Safety [5]. This

pollution alert is in effect.

document identified maximum levels of 55 decibels outdoors

and 45 decibels indoors to prevent interference with

USCB [3] reported that about 75% of homes in the

activities and 70 decibels for all areas to prevent hearing

United States used either utility gas or electricity for

loss. In 1990, the United Kingdom implemented The

heating purposes, with utility gas accounting for about

Household Appliances (Noise Emission) Regulations [6]

50%. This, of course, varies with the region of the

to help control indoor noise from modern appliances.

country, depending on the availability of hydroelectric

Noise has physiologic impacts aside from the potential to

power. This compares with the 1940 census, which found

reduce hearing ability. According to the American Speech-

that three-quarters of all households heated with coal or

Language-Hearing Association [7], these effects include

wood. Electric heat was so rare that it was not even an

elevated blood pressure; negative cardiovascular effects;

option on the census form of 1940. Today, coal has

increased breathing rates, digestion, and stomach

virtually disappeared as a household fuel. Wood all but

disturbances; ulcers; negative effects on developing

disappeared as a heating fuel in 1970, but made a modest

fetuses; difficulty sleeping after the noise stops; plus the

comeback at 4% nationally by 1990. This move over time

intensification of the effects of drugs, alcohol, aging, and

to more flexible fuels allows a majority of today’s homes

carbon monoxide. In addition, noise can reduce attention

to maintain healthy temperatures, although many houses

to tasks and impede speech communication. Finally, noise

still lack adequate insulation.

can hamper performance of daily tasks, increase fatigue,

and cause irritability.

The fifth through the seventh physiologic concerns

address adequate illumination, both natural and artificial.

Household noise can be controlled in various ways.

Research has revealed a strong relationship between light

Approaching the problem during initial construction is

and human physiology. The effects of light on both the

the simplest, but has not become popular. For example, in

human eye and human skin are notable. According to

early 2003, only about 30% of homebuilders offered

Zilber [4], one of the physiologic responses of the skin to

sound-attenuating blankets for interior walls. A sound-

sunlight is the production of vitamin D. Light allows us

attenuating blanket is a lining of noise abatement

to see. It also affects body rhythms and psychologic

products (the thickness depends on the material being used).

health. Average individuals are affected daily by both

Spray-in-place soft foam insulation can also be used as a

natural and artificial lighting levels in their homes.

sound dampener, as can special walking mats for floors.

Adequate lighting is important in allowing people to see

Actions that can help reduce household noise include

unsanitary conditions and to prevent injury, thus

installing new, quieter appliances and isolating washing

contributing to a healthier and safer environment.

machines to reduce noise and water passing through pipes.

Improper indoor lighting can also contribute to eyestrain

from inadequate illumination, glare, and flicker.

The ninth and final physiologic need is for adequate

space for exercise and play. Before industrialization in the

Avoiding excessive noise (eighth physiologic concern) is

United States and England, a preponderance of the

important in the 21st century. However, the concept of

population lived and worked in more rural areas with

noise pollution is not new. Two thousand years ago, Julius

very adequate areas for exercise and play. As

Caesar banned chariots from traveling the streets of Rome

industrialization impacted demographics, more people

late at night. In the 19th century, numerous towns and

were in cities without ample space for play and exercise.

cities prohibited ringing church bells. In the early 20th

In the 19th century, society responded with the

century, London prohibited church bells from ringing

development of playgrounds and public parks. Healthful

between 9:00 PM and 9:00 AM. In 1929, New York City

housing should include the provision of safe play and

2-2

Basic Principles of Healthy Housing

exercise areas. Many American neighborhoods are severely

Protection Against Disease

deficient, with no area for children to safely play. New

Eight ways to protect against contaminants include the

residential areas often do not have sidewalks or street

following:

lighting, nor are essential services available by foot

because of highway and road configurations.

1. provide a safe and sanitary water supply;

Fundamental Psychologic Needs

2. protect the water supply system against pollution;

Seven fundamental psychologic needs for healthy housing

include the following:

3. provide toilet facilities that minimize the danger

of transmitting disease;

1. adequate privacy for the individual,

4. protect against sewage contamination of the interior

2. opportunities for normal family life,

surfaces of the dwelling;

3. opportunities for normal community life,

5. avoid unsanitary conditions near the dwelling;

4. facilities that make possible the performance of

6. exclude vermin from the dwelling, which may

household tasks without undue physical and

play a part in transmitting disease;

mental fatigue,

7. provide facilities for keeping milk and food

5. facilities for maintenance of cleanliness of the

fresh; and

dwelling and of the person,

8. allow sufficient space in sleeping rooms to

6. possibilities for aesthetic satisfaction in the home

minimize the danger of contact infection.

and its surroundings, and

According to the U.S. EPA [8], there are approximately

7. concordance with prevailing social standards of

160,000 public or community drinking water systems in the

the local community.

United States. The current estimate is that 42 million

Americans (mostly in rural America) get their water from

Privacy is a necessity to most people, to some degree and

private wells or other small, unregulated water systems.

during some periods. The increase in house size and the

The presence of adequate water, sewer, and plumbing

diminishing family size have, in many instances, increased

facilities is central to the prevention, reduction, and possible

the availability of privacy. Ideally, everyone would have

elimination of water-related diseases. According to the

their own rooms, or, if that were not possible, would

Population Information Program [9], water-related diseases

share a bedroom with only one person of the same sex,

can be organized into four categories:

excepting married couples and small children. Psychiatrists

consider it important for children older than 2 years to

• waterborne diseases, including those caused by

have bedrooms separate from their parents. In addition,

both fecal-oral organisms and those caused by toxic

bedrooms and bathrooms should be accessible directly

substances;

from halls or living rooms and not through other bedrooms.

In addition to the psychologic value of privacy, repeated

• water-based diseases;

studies have shown that lack of space and quiet due to

crowding can lead to poor school performance in children.

• water-related vector diseases; and

Coupled with a natural desire for privacy is the social

• water-scarce diseases.

desire for normal family and community life. A wholesome

atmosphere requires adequate living room space and

Numerous studies link improvements in sanitation and the

adequate space for withdrawal elsewhere during periods of

provision of potable water with significant reductions in

entertainment. This accessibility expands beyond the walls

morbidity and mortality from water-related diseases.

of the home and includes easy communication with centers

Clean water and sanitation facilities have proven to

of culture and business, such as schools, churches,

reduce infant and child mortality by as much as 55%

entertainment, shopping, libraries, and medical services.

in Third World countries according to studies from the

Healthy Housing Reference Manual

2-3

1980s. Waterborne diseases are often referred to as “dirty-

Of the 13 million housing units at the time without flush

water” diseases and are the result of contamination from

toilets, 11.8 million (90.7%) had an outside toilet or

chemical, human, and animal wastes. Specific diseases

privy, another 1 million (7.6%) had no toilet or privy,

in this group include cholera, typhoid, shigella, polio,

and the remainder had a nonflush toilet in the structure.

meningitis, and hepatitis A and E. Water-based diseases

are caused by aquatic organisms that spend part of their

In contrast to these figures, the 2000 census data demonstrate

life cycle in the water and another part as parasites of

the great progress that has been made in providing sanitary

animals. Although rare in the United States, these

sewer facilities. Nationally, 74.8% of homes are served by

diseases include dracunculiasis, paragonimiasis,

a public sewer, with 24.1% served by a septic tank or cesspool,

clonorchiasis, and schistosomiasis. The reduction in these

and the remaining 1.1% using other means.

diseases in many countries has not only led to decreased rates

of illness and death, but has also increased productivity

Vermin, such as rodents, have long been linked to

through a reduction in days lost from work.

property destruction and disease. Integrated pest

management, along with proper housing construction, has

Water-related diseases are linked to vectors that breed and

played a significant role in reducing vermin around the

live in or near polluted and unpolluted water. These vectors are

modern home. Proper food storage, rat-proofing

primarily mosquitoes that infect people with the disease

construction, and ensuring good sanitation outside the

agents for malaria, yellow fever, dengue fever, and

home have served to eliminate or reduce rodent problems

filariasis. While the control of vectorborne diseases is a

in the 21st century home.

complex matter, in the United States, most of the control

focus has been on controlling habitat and breeding areas

Facilities to properly store milk and food have not only been

for the vectors and reducing and controlling human cases

instrumental in reducing the incidence of some foodborne

of the disease that can serve as hosts for the vector.

diseases, but have also significantly changed the diet in

Vectorborne diseases have recently become a more of a

developed countries. Refrigeration can be traced to the

concern to the United States with the importation of the

ancient Chinese, Hebrews, Greeks, and Romans. In the

West Nile virus. The transmission of West Nile virus

last 150 years, great strides have been made in using

occurs when a mosquito vector takes a blood meal from a bird

refrigeration to preserve and cool food. Vapor compression

or incidental hosts, such as a dog, cat, horse, or other

using air and, subsequently, ammonia as a coolant was

vertebrate. The human cases of West Nile virus in

first developed in the 1850s. In the early 1800s, natural

2003 numbered 9,862, with 264 deaths. Finally,

ice was extracted for use as a coolant and preserver of

water-scarce diseases are diseases that flourish where

food. By the late 1870s, there were 35 commercial ice

sanitation is poor due to a scarcity of fresh water. Diseases

plants in the United States and, by 1909, there were 2,000.

included in this category are diphtheria, leprosy, whooping

However, as early as the 1890s, sources of natural ice

cough, tetanus, tuberculosis, and trachoma. These

began to be a problem as a result of pollution and sewage

diseases are often transmitted when the supply of fresh

dumped into bodies of water. Thus, the use of natural ice as

water is inadequate for hand washing and basic hygiene.

a refrigerant began to present a health problem. Mechanical

These conditions are still rampant in much of the world,

manufacture of ice provided a temporary solution, which

but are essentially absent from the United States due to

eventually resulted in providing mechanical refrigeration.

the extensive availability of potable drinking water.

Refrigeration was first used by the brewing and meat-packing

In 2000, USCB [10] reported that 1.4% of U.S. homes

industries; but most households had iceboxes (Figure 2.1),

lacked plumbing facilities. This differs greatly from the

which made the ice wagon a popular icon of the late

1940 census, when nearly one-half of U.S. homes lacked

1800s and early 1900s. In 1915, the first refrigerator, the

complete plumbing. The proportion has continually

Guardian, was introduced. This unit was the predecessor of

dropped, falling to about one-third in 1950 and then to

the Frigidaire. The refrigerator became as necessary to the

one-sixth in 1960. Complete plumbing facilities are

household as a stove or sewing machine. By 1937, nearly

defined as hot and cold piped water, a bathtub or shower,

6 million refrigerators were manufactured in the United

and a flush toilet. The containment of household sewage

States. By 1950, in excess of 80% of American farms and

is instrumental in protecting the public from waterborne

more than 90% of urban homes had a refrigerator.

and vectorborne diseases. The 1940 census revealed that

more than a third of U.S. homes had no flush toilet, with

Adequate living and sleeping space are also important in

70% of the homes in some states without a flush toilet.

protecting against contagion. It is an issue not only of

2-4

Basic Principles of Healthy Housing

to the International Code Council one- and two-family

dwelling code, the purpose of building codes is to provide

minimum standards for the protection of life, limb,

property, environment, and for the safety and welfare of

the consumer, general public, and the owners and

occupants of residential buildings regulated by this

code [12].

However, as with all types of codes, the development of

innovative processes and products must be allowed to take

a place in improving construction technology. Thus,

according to the International Code Council one- and

two-family dwelling code, building codes are not

intended to limit the appropriate use of materials,

appliances, equipment, or methods by design or

construction that are not specifically prescribed by the

code if the building official determines that the proposed

alternate materials, appliances, equipment or methods of

design or construction are at least equivalent of that

prescribed in this code. While the details of what a code

should include are beyond the scope of this section,

additional information can be found at

Figure 2.1. Circa 1890 Icebox

Source: Robert R. McCormick Museum, Wheaton, Illinois

http://www.iccsafe.org/, the Web site of the International

Code Council (ICC). ICC is an organization formed by

privacy but of adequate room to reduce the potential for the

the consolidation of the Building Officials and Code

transmission of contagion. Much improvement has been

Administrators International, Southern Building Code

made in the adequacy of living space for the U.S. family

Congress International, Inc., and the International

over the last 30 years. According to USCB [11], the

Conference of Building Officials [12].

average size of new single homes has increased from a

1970 average of 1,500 square feet to a 2000 average of

According to the Home Safety Council (HSC) [13], the

2,266 square feet. USCB [11] says that slightly less than

leading causes of home injury deaths in 1998 were falls

5% of U.S. homes were considered crowded in 1990; that

and poisonings, which accounted for 6,756 and

is, they had more than one person per room. However,

5,758 deaths, respectively. As expected, the rates and

this is an increase since the 1980 census, when the figure

national estimates of the number of fall deaths were

was 4.5%. This is the only time there has been an

highest among those older than 64 years, and stairs or steps

increase since the first housing census was initiated in

were associated with 17% of fall deaths. Overall, falls were

1940, when one in five homes was crowded. During the

the leading cause of nonfatal, unintentional injuries

1940 census, most crowded homes were found in

occurring at home and accounted for 5.6 million injuries.

southern states, primarily in the rural south. Crowding

Similar to the mortality statistics, consumer products most

has become common in a few large urban areas, with

often associated with emergency department visits included

more than one-fourth of all crowded units located in four

stairs and steps, accounting for 854,631 visits, and floors,

metropolitan areas: Houston, Los Angeles, Miami, and

accounting for 556,800 visits. A national survey by HSC

New York. The rate for California has not changed

found that one-third of all households with stairs did not

significantly between 1940 (13%) and 1990 (12%).

have banisters or handrails on at least one set of stairs.

Excessive crowding in homes has the potential to increase

Related to this, homes with older persons were more

not only communicable disease transmission, but also the

likely to have banisters or handrails than were those where

stress level of occupants because modern urban

young children live or visit. The survey also revealed that

individuals spend considerably more time indoors than

48% of households have windows on the second floor or

did their 1940s counterparts.

above, but only 25% have window locks or bars to

prevent children from falling out. Bathtub mats or

Protection Against Injury

nonskid strips to reduce bathtub falls were used in 63%

A major provision for safe housing construction is

of American households. However, in senior households

developing and implementing building codes. According

Healthy Housing Reference Manual

2-5

(age 70 years and older), 79% used mats or nonskid strips.

•

using a metal mesh screen with fireplaces and

Nineteen percent of the total number of homes surveyed

leaving glass doors open while burning a fire;

had grab bars to supplement the mats and strips. Significantly,

only 39% of the group most susceptible to falls (people aged

•

installing stovepipe thermometers to monitor flue

70 years and older) used both nonskid surfaces and grab bars.

temperatures;

Protection Against Fire

•

leaving air inlets on wood stoves open and never

An important component of safe housing is to control

restricting air supply to the fireplaces, thus

conditions that promote the initiation and spread of fire.

helping to reduce creosote buildup;

Between 1992 and 2001, an average of 4,266 Americans

died annually in fires and nearly 25,000 were injured.

•

using fire-resistant materials on walls around

This fact and the following information from the United

wood stoves;

States Fire Administration (USFA) [14] demonstrate the

impact that fire safety and the lack of it have in the United

•

never using flammable liquids to start a fire;

States. The United States has one of the highest fire death

rates in the industrialized world, with 13.4 deaths per

•

using only seasoned hardwood rather than soft,

million people. At least 80% of all fire deaths occur in

moist wood, which accelerates creosote buildup;

residences. Residential fires account for 23% of all fires

and 76% of structure fires. In one- and two-family

•

building small fires that burn completely and

dwellings, fires start in the kitchen 25.5% of the time and

produce less smoke;

originate in the bedroom 13.7% of the time. Apartment

fires most often start in the kitchen, but at almost twice

•

never burning trash, debris, or pasteboard in a

the rate (48.5%), with bedrooms again being the second

fireplace;

most common place at 13.4%.

•

placing logs in the rear of the fireplace on an adequate

These USFA statistics also disclose that cooking is the

supporting grate;

leading cause of home fires, usually a result of unattended

cooking and human error rather than mechanical failure

•

never leaving a fire in the fireplace unattended;

of the cooking units. The leading cause of fire deaths in

homes is careless smoking, which can be significantly

•

keeping the roof clear of leaves, pine needles,

deterred by smoke alarms and smolder-resistant bedding

and other debris;

and upholstered furniture. Heating system fires tend to be

a larger problem in single-family homes than in

•

covering the chimney with a mesh screen spark

apartments because the heating systems in family homes

arrester;and

frequently are not professionally maintained.

•

removing branches hanging above the chimney,

A number of conditions in the household can contribute

flues, or vents.

to the creation or spread of fire. The USFA data indicate

that more than one-third of rural Americans use fireplaces,

USFA [14] also notes that manufactured homes can be

wood stoves, and other fuel-fired appliances as primary sources

susceptible to fires. More than one-fifth of residential fires

of heat. These same systems account for 36% of rural

in these facilities are related to the use of supplemental

residential fires. Many of these fires are the result of

room heaters, such as wood- and coal-burning stoves,

creosote buildup in chimneys and stovepipes. These fires

kerosene heaters, gas space-heaters, and electrical heaters.

could be avoided by

Most fires related to supplemental heating equipment result

from improper installation, maintenance, or use of the

• inspecting and cleaning by a certified chimney

appliance. USFA recommendations to reduce the chance

specialist;

of fire with these types of appliances include the following:

• clearing the area around the hearth of debris,

• placing wood stoves on noncombustible surfaces

decorations, and flammable materials;

or a code-specified or listed floor surface;

2-6

Basic Principles of Healthy Housing

• placing noncombustible materials around the

alarm is then triggered by the drop in current between the

opening and hearth of fireplaces;

plates [16].

• placing space heaters on firm, out-of-the-way

Photoelectric devices function in one of two ways. First, smoke

surfaces to reduce tipping over and subsequent

blocks a light beam, reducing the light reaching the photocell,

spillage of fuel and providing at least 3 feet of air

which sets off the alarm. In the second and more

space between the heating device and walls, chairs,

common type of photoelectric unit, smoke particles

firewood, and curtains;

scatter the light onto a photocell, initiating an alarm. Both

detector types are effective smoke sensors and both must

• placing vents and chimneys to allow 18 inches of air

pass the same test to be certified as Underwriters Laboratories

space between single-wall connector pipes and

(UL) smoke detectors. Ionization detectors respond more

combustibles and 2 inches between insulated

quickly to flaming fires with smaller combustion particles,

chimneys and combustibles; and

while photoelectric detectors respond more quickly to

smoldering fires. Detectors can be damaged by steam or high

• using only the fuel designated by the

temperatures. Photoelectric detectors are more expensive

manufacturer for the appliance.

than ionization detectors and are more sensitive to minute

smoke particles. However, ionization detectors have a

The ability to escape from a building when fire has been

degree of built-in security not inherent to photoelectric

discovered or detected is of extreme importance. In the

detectors. When the battery starts to fail in an ionization

modern home, three key elements can contribute to a safe

detector, the ion current falls and the alarm sounds,

exit from a home during the threat of fire. The first of

warning that it is time to change the battery before the

these is a working smoke alarm system. The average

detector becomes ineffective. Backup batteries may be used

homeowner in the 1960s had never heard of a smoke

for photoelectric detectors that are operated using the

alarm, but by the mid-1980s, laws in 38 states and in

home’s electrical system.

thousands of municipalities required smoke alarms in all

new and existing residences. By 1995, 93% of all single-

According to USFA [14], a properly functioning smoke

family and multifamily homes, apartments, nursing

alarm diminishes the risk for dying in a fire by

homes, and dormitories were equipped with alarms. The

approximately 50% and is considered the single most

cost decreased from $1,000 for a professionally installed unit

important means of preventing house and apartment fire

for a three-bedroom home in the 1970s to an owner-

fatalities. Proper installation and maintenance, however,

installed $10 unit. According to the EPA [15],

are key to their usefulness. Figure 2.2 shows a typical smoke

ionization chamber and photoelectric are the two most

alarm being tested.

common smoke detectors available commercially.

Helmenstein [16] states that a smoke alarm uses one or

Following are key issues regarding installation and

both methods, and occasionally uses a heat detector, to

maintenance of smoke alarms. (Smoke alarms should be

warn of a fire. These units can be powered by a 9-volt battery,

installed on every level of the home including the

a lithium battery, or 120-volt house wiring. Ionization

basement, both inside and outside the sleeping area.)

detectors function using an ionization chamber and a minute

source of ionizing radiation. The radiation source is

• Smoke alarms should be installed on the ceiling or

americium-241 (perhaps 1/5,000th of a gram), while the

6-8 inches below the ceiling on side walls.

ionization chamber consists of two plates separated by about a

centimeter. The power source (battery or house current)

• Battery replacement is imperative to ensuring proper

applies voltage to the plates, resulting in one plate being

operation. Typically, batteries should be replaced at

charged positively while the other plate is charged negatively.

least once a year, although some units are

The americium constantly releases alpha particles that knock

manufactured with a 10-year battery. A “chirping”

electrons off the atoms in the air, ionizing the oxygen and

noise from the unit indicates the need for battery

nitrogen atoms in the chamber. The negative plate attracts

replacement. A battery-operated smoke alarm has a

the positively charged oxygen and nitrogen atoms, while the

life expectancy of 8 to 10 years.

electrons are attracted to the positive plate, generating a

small, continuous electric current. If smoke enters the

• Battery replacement is not necessary in units that

ionization chamber, the smoke particles attach to the ions

are connected to the household electrical system.

and neutralize them, so they do not reach the plate. The

Healthy Housing Reference Manual

2-7

the National Fire Protection Association (NFPA) [17],

electrical distribution equipment was the third-leading

cause of home fires and the second-leading cause of fire

deaths in the United States between 1994 and 1998.

Specifically, NFPA reported that 38,300 home electrical

fires occurred in 1998, which resulted in 284 deaths,

1,184 injuries, and approximately $670 million in direct

property damage. The same report indicated that the

leading cause of electrical distribution fires was ground

fault or short-circuit problems. A third of the home

electrical distribution fires were a result of problems with

fixed wiring, while cords and plugs were responsible for

17% of these fires and 28% of the deaths.

Additional investigation of these statistics reveals that

electrical fires are one of the leading types of home fires in

Figure 2.2. Smoke Alarm Testing

Source: Federal Emergency Management Agency

manufactured homes. USFA [14] data demonstrate that

many electrical fires in homes are associated with

• Regardless of the type, it is crucial to test every smoke

improper installation of electrical devices by do-it-

alarm monthly. Data from HSC [13] revealed that

yourselfers. Errors attributed to this amateur electrical

only 83% of individuals with fire alarms test them

work include use of improperly rated devices such as

at least once a year; while only 19% of households

switches or receptacles and loose connections leading to

with at least one smoke alarm test them quarterly.

overheating and arcing, resulting in fires. Recommendations

to reduce the risk of electrical fires and electrocution

A second element impacting escape from a building is a

include the following:

properly installed fire-suppression system. According to USFA

[14], sprinkler systems began to be used over 100 years ago in

Use only the correct fuse size and do not use

New England textile mills. Currently, few homes are protected

pennies behind a fuse.

by residential sprinkler systems. However, UL-listed home

systems are available and are designed to protect homes much

Install ground fault circuit interrupters (GFCI) on

faster than standard commercial or industrial sprinklers. Based

all outlets in kitchens, bathrooms, and anywhere

on approximately 1% of the total building price in new

else near water. This can also be accomplished by

construction, sprinkler systems can be installed for a

installing a GFCI in the breaker box, thus

reasonable price. These systems can be retrofitted to

protecting an entire circuit.

existing construction and are smaller than commercial

systems. In addition, homeowner insurance discounts for

Never place combustible materials near light

such systems range between 5% and 15% and are

fixtures, especially halogen bulbs that get very hot.

increasing in availability.

Use only the correct bulb size in a light fixture.

The final element in escaping from a residential fire is having a

fire plan. A 1999 survey conducted by USFA [14] found

Use only properly rated extension cords for the

that 60% of Americans have an escape plan, with 42% of

job needed.

these individuals having practiced the plan. Surprisingly,

26% of Americans stated they had never thought about

Never use extension cords as a long-term solution

practicing an escape plan, and 3% believed escape

to the need for an additional outlet. Size the

planning to be unnecessary. In addition, of the people

extension cord to the wattage to be used.

who had a smoke alarm sound an alert over the past year

before the study, only 8% believed it to be a fire and

Never run extension cords inside walls or under

thought they should evacuate the building.

rugs because they generate heat that must be able

to dissipate.

Protection from electrical shocks and burns is also a vital

element in the overall safety of the home. According to

2-8

Basic Principles of Healthy Housing

Fire Extinguishers

an electrical cord and outlet with a slash through it (do not

A fire extinguisher should be listed and labeled by an

use it on an electrical fire).

independent testing laboratory such as FM (Factory

Mutual) or UL. Fire extinguishers are labeled according to

Fire extinguishers also have a number rating. For Type A

the type of fire on which they may be used. Fires involving

fires, 1 means 1¼ gallons of water; 2 means 2½ gallons of

wood or cloth, flammable liquids, electrical, or metal sources

water, 3 means 3¾ gallons of water, etc. For Type B and

react differently to extinguishers. Using the wrong type of

Type C fires, the number represents square feet. For example,

extinguisher on a fire could be dangerous and could worsen

2 equals 2 square feet, 5 equals 5 square feet, etc.

the fire. Traditionally, the labels A, B, C, and D have been

used to indicate the type of fire on which an extinguisher

Fire extinguishers can also be made to extinguish more

is to be used.

than one type of fire. For example, you might have an

extinguisher with a label that reads 2A5B. This would

Type A—Used for ordinary combustibles such as cloth,

mean this extinguisher is good for Type A fires with a

wood, rubber, and many plastics. These types of fire

2½-gallon equivalence and it is also good for Type B fires

usually leave ashes after they burn: Type A extinguishers

with a 5-square-foot equivalency. A good extinguisher to

for ashes. The Type A label is in a triangle on the

have in each residential kitchen is a 2A10BC fire extinguisher.

extinguisher.

You might also get a Type A for the living room and

bedrooms and an ABC for the basement and garage.

Type B—Used for flammable liquid fires such as oil,

gasoline, paints, lacquers, grease, and solvents. These

PASS is a simple acronym to remind you how to operate most

substances often come in barrels: Type B extinguishers for

fire extinguishers—pull, aim, squeeze, and sweep. Pull the

barrels. The Type B label is in a square on the

pin at the top of the cylinder. Some units require the

extinguisher.

releasing of a lock latch or pressing a puncture lever. Aim

the nozzle at the base of the fire. Squeeze or press the

Type C—Used for electrical fires such as in wiring, fuse boxes,

handle. Sweep the contents from side to side at the base

energized electrical equipment, and other electrical sources.

of the fire until it goes out. Shut off the extinguisher and

Electricity travels in currents; Type C extinguishers for

then watch carefully for any rekindling of the fire.

currents. The Type C label is in a circle on the

extinguisher.

Protection Against Toxic Gases

Protection against gas poisoning has been a problem since

Type D—Used for metal fires such as magnesium,

the use of fossil fuels was combined with relatively tight

titanium, and sodium. These types of fires are very dangerous

housing construction. NFPA [17] notes that National

and seldom handled by the general public; Type D means

Safety Council statistics reflect unintentional poisonings

don’t get involved. The Type D label is in a star on the

by gas or vapors, chiefly carbon monoxide (CO),

extinguisher.

numbering about 600 in 1998. One-fourth of these

involved heating or cooking equipment in the home. The

The higher the rating number on an A or B fire extinguisher,

U.S. Consumer Product Safety Commission [18] states

the more fire it can put out, but high-rated units are often

that in 2001 an estimated 130 deaths occurred as a result

the heavier models. Extinguishers need care and must be

of CO poisoning from residential sources; this decrease in

recharged after every use—a partially used unit might as

deaths is related to the increased use of CO detectors. In

well be empty. An extinguisher should be placed in the

addition, approximately 10,000 cases of CO-related injuries

kitchen and in the garage or workshop. Each extinguisher

occur each year. NFPA [17] also notes that, similar to fire

should be installed in plain view near an escape route and

deaths, unintentional CO deaths are highest for ages 4 years

away from potential fire hazards such as heating appliances.

and under and ages 75 years and older. Additional information

about home CO monitoring can be found in Chapter 5.

Recently, pictograms have come into use on fire extinguishers.

These picture the type of fire on which an extinguisher is

References

to be used. For instance, a Type A extinguisher has a

1. Ehlers VE, Steel EW. Municipal and rural

pictogram showing burning wood. A Type C extinguisher has

sanitation. Sixth edition. New York: McGraw-Hill

a pictogram showing an electrical cord and outlet. These

Book Company; 1965. p. 462-4.

pictograms are also used to show what not to use. For

example, a Type A extinguisher also show a pictogram of

Healthy Housing Reference Manual

2-9

National Institute on Aging. Hyperthermia—too

11. US Census Bureau. Historical census of housing

hot for your health, fact sheet health information.

tables—crowded and severely crowded housing

Bethesda, MD: US Department of Health and

units, 2002. Washington, DC: US Census

Human Services; no date. Available from URL:

Bureau; 2003. Available from URL:

http://www.niapublications.org/engagepages/

http://www.census.gov/hhes/ www/housing/

hyperther.asp.

census/historic/crowding.html.

US Census Bureau. Historical census of housing

12. International Code Council. Fact sheet. Falls

tables—house heating fuel. Washington, DC: US

Church, VA: International Code Council; no date.

Census Bureau; 2002. Available from URL:

Available from URL: http://www.iccsafe.org/news/pdf/

http://www.census.gov/hhes/www/housing/

factssheet.pdf.

census/historic/fuels.html.

13. Home Safety Council. The state of home safety in

Zilber SA. Review of health effects of indoor

America—executive summary. Washington, DC:

lighting. Architronic 1993;2(3). Available from URL:

The Home Safety Council; 2002.

http://architronic.saed.kent.edu/v2n3/v2n3.06.html.

14. US Fire Administration. Welcome to the U.S. Fire

US Environmental Protection Agency.

Administration (USFA) Web site. Washington,

Information on levels of environmental noise

DC: Federal Emergency Management Agency,

requisite to protect public health and welfare with

Department of Homeland Security; 2003.

an adequate margin of safety. Washington, DC: US

Available from URL: http://www.usfa.fema.gov/.

Environmental Protection Agency; 1974.

15. US Environmental Protection Agency. Smoke

Public Health, England and Wales. The Household

detectors and radiation. Washington, DC: US

Appliances (Noise Emission) Regulations 1990.

Environmental Protection Agency; 2003. Available

London: Her Majesty’s Stationery Office; 1990.

from URL: http://www.epa.gov/

radiation/sources/smoke_alarm.htm.

American Speech-Language-Hearing-Association.

Noise: noise is difficult to define. Rockville, MD:

16. Helmenstein AM. How do smoke detectors work?

American Speech-Language-Hearing-Association;

Photoelectric & ionization smoke detectors, what

2003. Available from URL: http://www.asha.org/

you need to know about chemistry. New York:

public/hearing/disorders/noise.htm.

About, Inc.; 2003. Available from URL:

http://chemistry.about.com/library/weekly/

US Environmental Protection Agency. Factoids:

aa071401a.htm.

drinking water and ground water statistics for

2002. Washington, DC: US Environmental

17. National Fire Protection Association. NFPA fact

Protection Agency, Office of Ground Water and

sheets—electrical safety. Quincy, MA: National

Drinking Water; January 2003. Available from URL:

Fire Protection Association; 2003. Available from

http://www.epa.gov/safewater.

URL: http://www.nfpa.org/Research/

NFPAFactSheets/Electrical/electrical.asp.

Hinrichsen D, Robey B, Upadhyay UD. The health

dimension. In: Solutions for a water-short world.

18. US Consumer Product Safety Commission.

Population Report, Series M, No. 14. Baltimore, MD:

Nonfire carbon monoxide deaths: 2001 annual

Johns Hopkins School of Public Health, Population

estimate. Washington, DC: US Consumer

Information Program; 1998. Available from URL:

Product Safety Commission; 2004. Available from

http://www.infoforhealth.org/pr/m14/m14chap5.shtml

URL: http://www.cpsc.gov/LIBRARY/co04.pdf.

10. US Census Bureau. Historical census of housing

tables—plumbing facilities, 2002. Washington,

DC: US Census Bureau; 2003. Available from URL:

http://www.census.gov/hhes/www/housing/census/

historic/plumbing.html.

2-10

Basic Principles of Healthy Housing

Additional Sources of Information

Barbalace RC. Environmental justice and the NIMBY

principle. Environmental Chemistry.com: Environmental,

Chemistry, and Hazardous Materials Information and

Resources. Portland, ME; no date. Available from URL:

http://environmentalchemistry.com/yogi/hazmat/articles/

nimby.html.

Bryant B. The role of SNRE in the environmental justice

movement. Ann Arbor, MI: University of Michigan; 1997.

Available from URL: http://www.umich.edu/~snre492/

history.html.

Bullard RD. Waste and racism: a stacked deck? Forum

Appl Res Public Pol spring 1993.

National Institute on Aging. Hypothermia: a cold weather

hazard, fact sheet health information. Bethesda, MD: US

Department of Health and Human Services; 2001.

Available from URL: http://www.niapublications.org/

engagepages/ hypother.asp.

National Weather Service. Natural hazard statistics; no

date. Silver Spring, MD: National Weather Service.

Available from URL: http://www.nws.noaa.gov/

om/hazstats.shtml.

US Census Bureau. New residential construction

(building permits, housing starts, and housing

completions). Washington, DC: US Census Bureau; no

date. Available from URL:

http://www.census.gov/newresconst.

Healthy Housing Reference Manual

2-11

Chapter 3: Housing Regulations

“The poorest man may in his cottage bid defiance to all the

the first tenements were built. In 1867, a report by the

force of the Crown. It may be frail—its roof may shake—the

New York Metropolitan Board of Health on living

wind may blow through it—the storm may enter, the rain

conditions in tenements convinced the New York State

may enter—but the King of England cannot enter—all his

legislature to pass the Tenement Housing Act of 1867 [2].

force dares not cross the threshold of the ruined tenement!”

The principal requirements of the act included the

following:

William Pitt, March 1763

•

Every room occupied for sleeping, if it does not

Introduction

communicate directly with the external air, must

William Pitt, arguing before the British Parliament against

have a ventilating or transom window of at least

excise officers entering private homes to levy the Cyder

3 square feet to the neighboring room or hall.

Tax, eloquently articulated this long-held and cherished

notion of the sanctity of private property. However, a

•

A proper fire escape is necessary on every tenement

person’s right to privacy is not absolute. There has always

or lodging house.

been a tension between the rights of property owners to do

whatever they desire with their property and the ability of

•

The roof is to be kept in repair and the stairs are to

the government to regulate uses to protect the safety,

have banisters.

health, and welfare of the community. Few, however,

would argue with the right and duty of a city government

•

At least one toilet is required for every

to prohibit the operation of a munitions factory or a

20 occupants for all such houses, and those toilets

chemical plant in the middle of a crowded residential

must be connected to approved disposal systems.

neighborhood.

•

Cleansing of every lodging house is to be to the

History

satisfaction of the Board of Health, which is to have

The first known housing laws are in the Code of Laws of

access at any time.

Hammurabi [1], who was the King of Babylonia, circa

1792-1750 BC. These laws addressed the responsibility of the

•

All cases of infectious disease are to be reported to

home builder to construct a quality home and outlined the

the Board by the owner or his agent; buildings are

implications to the builder if injury or harm came to the

to be inspected and, if necessary, disinfected or

owner as a result of the failure to do so. During the Puritan

vacated if found to be out of repair.

period (about 1620-1690), housing laws essentially

governed the behavior of the members of the society. For

There were also regulations governing distances between

example, no one was allowed to live alone, so bachelors,

buildings, heights of rooms, and dimensions of windows.

widows, and widowers were placed with other families as

Although this act had some beneficial influences on

servants or boarders. In 1652, Boston prohibited building

overcrowding, sewage disposal, lighting, and ventilation,

privies within 12 feet of the street. Around the turn of the

perhaps its greatest contribution was in laying a foundation

18th century, some New England communities

for more stringent future legislation.

implemented local ordinances that specified the size of

houses. During the 17th century, additional public policies

Jacob A. Riis, a Danish immigrant and a police reporter on

on housing were established. Because the English tradition

New York’s Lower East Side, published a book titled How

of using wooden chimneys and thatched roofs led to fires

the Other Half Lives—Studies Among the Tenements of New

in many dwellings, several colonies passed regulations

York [3], which swayed public opinion in the direction of

prohibiting them.

housing reform and resulted in the Tenement House Act of

1901. The basic principles established in the Tenement

After the early 17th century came an era of very rapid

House Act of 1901 still underlie much of the housing

metropolitan growth along the East Coast. This growth

efforts in New York City today [4]. Since 1909, with the

was due largely to immigration from Europe and was

establishment of the Philadelphia Housing Association, that city

spurred by the Industrial Revolution. The most serious

has had almost continual inspection and improvement.

housing problems began in New York about 1840 when

Chicago enacted housing legislation as early as 1889 and

Healthy Housing Reference Manual

3-1

health legislation as early as 1881. Regulations on

The Housing Act of 1949 allowed “primarily residential”

ventilation, light, drainage, and plumbing were put into

and “blighted” urban areas to be condemned, cleared of

effect in 1896.

buildings, and sold for private development. In addition

to assisting in slum clearance, this act also provided for

Before 1892, all government involvement in housing was

additional public housing and authorized the USDA to

at a local level. In 1892, however, the federal government

provide farmers with loans to construct, improve, repair

passed a resolution authorizing investigation of slum

or replace dwellings to provide decent, safe, and sanitary

conditions in cities with 200,000 or more inhabitants.

living conditions for themselves, their tenants, lessees,

Congress appropriated only $20,000 (roughly equal to

sharecroppers, and laborers.

$390,000 in 2003) to cover the expenses of this project,

which limited the number of investigations.

Because the many housing responsibilities administered

by various agencies within the federal government proved

No significant housing legislation was passed in the

unwieldy, the Housing and Urban Development Act was

20th century until 1929 [5], when the New York State

passed in 1965. The U.S. Department of Housing and

legislature passed its Multiple Dwelling Law. Other cities

Urban Development (HUD) was created to centralize the

and states followed New York’s example and permitted

responsibilities of the Housing and Home Finance Agency

less strict requirements in their codes. This decreased

and incorporated the FHA, the Federal National

what little emphasis there was on enforcement.

Mortgage Association, the Public Housing Administration,

Conditions declined until, by the 1930s, President

Urban Development Administration, and the Community

Franklin D. Roosevelt’s shocking report to the people was

Facilities Administration.

“that one-third of the nation is ill-fed, ill-housed, and ill-

clothed.” In response to the overwhelming loss of homes

Zoning, Housing Codes, and Building Codes

during the Great Depression, Congress passed the United

Housing is inextricably linked to the land on which it is

States Housing Act of 1937, which created the United

located. Changes in the patterns of land use in the United

States Housing Authority (USHA). This act subsidized

States, shifting demographics, an awareness of the need

construction of new public housing units and required

for environmental stewardship, and competing uses for

the elimination of at least an equivalent number of units

increasingly scarce (desirable) land have all placed added

from the local housing supply that were determined to be

stress on the traditional relationship between the property

inferior. In 1942, the USHA was renamed the Federal

owner and the community. This is certainly not a new

Public Housing Administration and, in 1947, was

development.

renamed the Public Housing Administration.

In the early settlement of this country, following the precedent

The federal government not only encouraged the

set by their forefathers from Great Britain, gunpowder

construction of public housing, but took on the role of

mills and storehouses were prohibited from the heavily

financing private housing. In 1938, the Federal National

populated portions of towns, owing to the frequent fires and

Mortgage Association was created. (Fannie Mae became a

explosions. Later, zoning took the form of fire districts

private organization in 1968 [6].) Its purpose was to

and, under implied legislative powers, wooden buildings

provide a secondary market for the FHA, created in 1934,

were prohibited from certain sections of a municipality.

and Veterans Administration (VA) mortgage loans. The

Massachusetts passed one of the first zoning laws in 1692.

Servicemen’s Readjustment Act of 1944, also known as

This law authorized Boston, Salem, Charlestown, and

the GI Bill of Rights, created a VA loan program

certain other market towns in the province to restrict the

guaranteeing home mortgage loans for veterans. This

establishment of slaughterhouses and stillhouses for

legislation, in conjunction with the FHA loan program,

currying leather to certain locations in each town.

was the impetus for initiating the huge program of home

construction and subsequent suburban growth following

Few people objected to such restrictions. Still, the tension

World War II. In 1946, the Farmers Home Administration,

remained between the right to use one’s land and the

housed in the United States Department of Agriculture

community’s right to protect its citizens. In 1926, the

(USDA), was created to make loans and grants for

United States Supreme Court took up the issue in Village

constructing and repairing farm homes and assisting rural

of Euclid, Ohio, v. Ambler Realty [7]. In this decision,

self-help housing groups.

the Court noted,

3-2

Housing Regulations

“Until recent years, urban life was comparatively

many cases, the housing inspector may be able to

simple; but with great increase and concentration of

eliminate violations or properties in violation of housing

population, problems have developed which require

codes through enforcement of the zoning ordinance.

additional restrictions in respect of the use and

occupation of private lands in urban communities.”

Zoning Objectives

As stated earlier, the purpose of a zoning ordinance is to

In explaining its reasoning, the Court said,

ensure that the land uses within a community are

regulated not only for the health, safety, and welfare of the

“the law of nuisances may be consulted not for the

community, but also are in keeping with the

purpose of controlling, but for the helpful aid of its

comprehensive plan for community development. The

analogies in the process of ascertaining the scope of the

provisions in a zoning ordinance that help to achieve

police power. Thus the question of whether the

development that provides for health, safety, and welfare

power exists to forbid the erection of a building of a

are designed to do the following:

particular kind or a particular use is to be

determined, not by an abstract consideration of the

•

Regulate height, bulk, and area of structure. To

building or other thing considered apart, but by

provide established standards for healthful housing

considering it in connection with the circumstances

within the community, regulations dealing with

and the locality… A nuisance may be merely the

building heights, lot coverage, and floor areas must

right thing in the wrong place—like a pig in the

be established. These regulations then ensure that

parlor instead of the barnyard.”

adequate natural lighting, ventilation, privacy, and

recreational areas for children will be realized.

Zoning, housing, and building codes were adopted to improve

These are all fundamental physiologic needs

the health and safety of people living in communities.

necessary for a healthful environment. Safety from

And, to some extent, they have performed this function.

fires is enhanced by separating buildings to meet

Certainly, housing and building codes, when enforced,

yard and open-space requirements. Through

have resulted in better constructed and maintained

requiring a minimum lot area per dwelling unit,

buildings. Zoning codes have been effective in

population density controls are established.

segregating noxious and dangerous enterprises from

residential areas. However, as the U.S. population has

•

Avoid undue levels of noise, vibration, glare, air

grown and changed from a rural to an urban then to a

pollution, and odor. By providing land-use

suburban society, land use and building regulations

category districts, these environmental stresses upon

developed for the 19th and early 20th centuries are

the individual can be reduced.

creating new health and safety problems not envisioned in

earlier times.

•

Lessen street congestion by requiring off-street

parking and off-street loading.

Zoning and Zoning Ordinances

Zoning is essentially a means of ensuring that a community’s

•

Facilitate adequate provision of water, sewerage,

land uses are compatible with the health, safety, and

schools, parks, and playgrounds.

general welfare of the community. Experience has shown

that some types of controls are needed to provide orderly

•

Provide safety from flooding.

growth in relation to the community plan for development.

Just as a capital improvement program governs public

•

Conserve property values. Through careful

improvements such as streets, parks and other recreational

enforcement of the zoning ordinance provisions,

facilities, schools, and public buildings, so zoning governs

property values can be stabilized and conserved.

the planning program with respect to the use of public

and private property.

To understand more fully the difference between zoning

and subdivision regulations, building codes, and housing

It is very important that housing inspectors know the general

ordinances, the housing inspector must know what cannot

nature of zoning regulations because properties in

be accomplished by a zoning ordinance. Items that

violation of both the housing code and the zoning ordinance

cannot be accomplished by a zoning ordinance include

must be brought into full compliance with the zoning

the following:

ordinance before the housing code can be enforced. In

Healthy Housing Reference Manual

3-3

• Overcrowding or substandard housing. Zoning

These initiatives are often called smart growth programs.

is not retroactive and cannot correct existing

It is imperative, if this approach is taken, that both

conditions. These are corrected through

governmental officials and citizens be involved in the

enforcement of a minimum standards housing code.

planning stage. Without this involvement, the community

may end up with major problems, such as overloaded

• Materials and methods of construction. Materials

infrastructure, structures of inappropriate construction

and methods of construction are enforced through

crowded together, and fire and security issues for

building codes rather than through zoning.

residents. Increased density could strain the existing water,

sewer and waste collection systems, as well as fire and

• Cost of construction. Quality of construction,

police services, unless proper planning is implemented.

and hence construction costs, are often regulated

through deed restrictions or covenants. Zoning

In recent years, some ordinances have been partially based

does, however, stabilize property values in an area

on performance standards rather than solely on land-use

by prohibiting incompatible development, such as

intensity. For example, some types of industrial developments

heavy industry in the midst of a well-established

may be permitted in a less intense use district provided

subdivision.

that the proposed land use creates no noise, glare, smoke,

dust, vibration, or other environmental stress exceeding

• Subdivision design and layout. Design and layout

acceptable standards and provided further that adequate

of subdivisions, as well as provisions for parks and

off-street parking, screening, landscaping, and similar

streets, are controlled through subdivision

measures are taken.

regulations.

Bulk and Height Requirements. Most early zoning

Content of the Zoning Ordinance

ordinances stated that, within a particular district, the

Zoning ordinances establish districts of whatever size,

height and bulk of any structure could not exceed certain

shape, and number the municipality deems best for

dimensions and specified dimensions for front, side, and

carrying out the purposes of the zoning ordinance. Most

rear yards. Another approach was to use floor-area ratios

cities use three major districts: residential (R), commercial

for regulation. A floor-area ratio is the relation between

(C), and industrial (I). These three may then be

the floor space of the structure and the size of the lot on

subdivided into many subdistricts, depending on local

which it is located. For example, a floor-area ratio of

conditions; e.g., R-1 (single-unit dwellings), R-2

1 would permit either a two-story building covering 50%

(duplexes), R-3 (low-rise apartment buildings), and so on.

of the lot, or a one-story building covering 100% of the lot, as

These districts specify the principal and accessory uses,

demonstrated in Figure 3.1. Other zoning ordinances

exceptions, and prohibitions [8].

specify the maximum amount of the lot that can be

covered or merely require that a certain amount of open

In general, permitted land uses are based on the intensity

space must be provided for each structure, and leave the

of land use—a less intense land use being permitted in a

builder the flexibility to determine the location of the

more intense district, but not vice versa. For example, a

structure. Still other ordinances, rather than specify a

single-unit residence is a less intense land use than a multiunit

particular height for the structure, specify the angle of

dwelling (defined by HUD as more than four living

light obstruction that will assure adequate air and light to

units) and hence would be permitted in a residential

the surrounding structures, as demonstrated in Figure 3.2.

district zoned for more intense land use (e.g., R-3). A

multiunit dwelling would not, however, be permitted in

Yard Requirements. Zoning ordinances also contain

an R-1 district. While intended to promote the health,

minimum requirements for front, rear, and side yards. These

safety, and general welfare of the community, housing

requirements, in addition to stating the lot dimensions,

trends in the last half of the 20th century have led a

usually designate the amount of setback required. Most

number of public health and planning officials to

ordinances permit the erection of auxiliary buildings in

question the blind enforcement of zoning districts. These

rear yards provided that they are located at stated

individuals, citing such problems as urban sprawl, have

distances from all lot lines and provided sufficient open

stated that municipalities need to adopt a more flexible

space is maintained. If the property is a corner lot,

approach to land use regulation—one that encourages

additional requirements are established to allow visibility

creating mixed-use spaces, increasing population densities,

for motorists.

and reducing reliance on the automobile.

3-4

Housing Regulations

Figure 3.1. Example of a Floor Area

Off-street Parking. Space for off-street parking and off-

another nonconforming use. Some zoning ordinances

street loading, especially for commercial buildings, is also

further provide a period of amortization during which

contained in zoning ordinances. These requirements are

nonconforming land use must be phased out.

based on the relationship of floor space or seating capacity

to land use. For example, a furniture store would require

Variances

fewer off-street parking spaces in relation to the floor area

Zoning ordinances contain provisions for permitting

than would a movie theater.

variances and providing a method for granting these

variances, subject to certain specified provisions. A

Exceptions to the Zoning Code

variance may be granted when, owing to the specific conditions

Nonconforming Uses

or use of a particular lot, an undue hardship would be

Because zoning is not retroactive, all zoning ordinances

imposed on the owner if the exact content of the

contain a provision for nonconforming uses. If a use has

ordinance is enforced. A variance may be granted due to

already been established within a particular district before the

the shape, topography, or other characteristic of the lot.

adoption of the ordinance, it must be permitted to

For example, suppose an irregularly shaped lot is located

continue, unless it can be shown to be a public nuisance.

in a district having a side yard requirement of 20 feet on a

side and a total lot size requirement of 10,000 square feet.

Provisions are, however, put into the ordinance to aid in

Further suppose that this lot contains 10,200 square feet

eliminating nonconforming uses over time. These

(and thus meets the total size requirement); however, due

provisions generally prohibit a) an enlargement or

to the irregular shape of the lot, there would be sufficient

expansion of the nonconforming use, b) reconstruction of

space for only a 15-foot side yard. Because a hardship

the nonconforming use if more than a certain portion of

would be imposed on the owner if the exact letter of the

the building should be destroyed, c) resumption of the

law is applied, the owner of the property could apply to

use after it has been abandoned for a period of specified

the zoning adjustment board for a variance. Because the

time, and d) changing the use to a higher classification or to

total area of the lot is sufficient and a lessening of the

Figure 3.2. Example of an Angle of Light Obstruction

Healthy Housing Reference Manual

3-5

ordinance requirements would not be detrimental to the

It is critical for the housing or building inspector and the

surrounding property, nor would it interfere with neighboring

zoning inspector to work closely in municipalities where

properties, a variance would probably be granted. Note

these positions and responsibilities are separate. Experience

that a variance is granted to the owner under specific

has shown that illegally converted properties are often

conditions. Should use of the property change, the

among the most substandard encountered in the municipality

variance would be voided.

and often contain especially dangerous housing code violations.

Exceptions

In communities where the zoning code is enforced effectively,

An exception is often confused with a variance. In every

the resulting zoning compliance helps to advance, as well

city there are some necessary uses that do not correspond

as sustain, many of the minimum standards of the

to the permitted land uses within the district. The zoning

housing code such as occupancy, ventilation, light, and

code recognizes, however, that if proper safeguards are

unimpeded egress. By the same token, building or

provided, these uses would not have a detrimental effect

housing inspectors can often aid the zoning inspector by

on the district. An example would be a fire station that

helping eliminate some nonconforming uses through code

could be permitted in a residential area, provided the

enforcement.

station house is designed and the property is properly

landscaped to resemble or fit in with the characteristics of the

Housing Codes

neighborhood in which it is located.

A housing code, regardless of who promulgates it, is basically

an environmental health protection code. Housing codes

Administration

are distinguished from building codes in that they cover

Zoning inspectors are essential to the zoning process

houses, not buildings in general. For example, the housing

because they have firsthand knowledge of a case. Often,

code requires that walls support the weight of the roof,

the zoning inspector may also be the building inspector or

any floors above, and the furnishings, occupants, etc.,

housing inspector. Because the building inspector or

within a building.

housing inspector is already in the field making

inspections, it is relatively easy for that individual to

Early housing codes primarily protected only physical health;

check compliance with the zoning ordinances. Compliance

hence, they were enforced only in slum areas. In the

is determined by comparing the actual land use with that

1970s, it was realized that, if urban blight and its associated

allowed for the area and shown on the zoning map.

human suffering were to be controlled, housing codes

must consider both physical and mental health and must

Each zoning ordinance has a map detailing the permitted

be administered uniformly throughout the community.

usage for each block. Using a copy of this map, the

inspector can make a preliminary check of the land use in

In preparing or revising housing codes, local officials must

the field. If the use does not conform, the inspector must

maintain a level of standards that will not merely be

then contact the Zoning Board to see whether the property in

minimal. Standards should maintain a living environment

question was a nonconforming use at the time of the

that contributes positively to healthful individual and

passage of the ordinance and whether an exception or variance

family living. The fact that a small portion of housing

has been granted. In cities where up-to-date records are

fails to meet a desirable standard is not a legitimate reason

maintained, the inspector can check the use in the field.

for retrogressive modification or abolition of a standard.

The adoption of a housing ordinance that establishes low

When a violation is observed, and the property owners

standards for existing housing serves only to legalize and

are duly notified of the violation, they have the right to

perpetuate an unhealthy living environment. Wherever

request a hearing before the Zoning Board of Adjustment

local conditions are such that immediate enforcement of

(also called the Zoning Board of Appeals in some cities).

some standards within the code would cause undue

The board may uphold the zoning enforcement officer or

hardship for some individuals, it is better to allow some

may rule in favor of the property owner. If the action of

time for compliance than to eliminate an otherwise

the zoning officer is upheld, the property owner may, if

satisfactory standard. When immediate health or safety

desired, seek relief by appealing the decision to the courts;

hazards are not involved, it is often wise to attempt to

otherwise, the violation must be corrected to conform to

create a reasonable timetable for accomplishing necessary

the zoning code.

code modifications.

3-6

Housing Regulations

History

dwellings were needed. Commonly called housing codes,

To assist municipalities with developing legislation necessary

these ordinances establish minimum standards to make

to regulate the quality of housing, the American Public

dwellings safe, sanitary, and fit for human habitation by

Health Association (APHA) Committee on the Hygiene

governing their condition and maintenance, their

of Housing prepared and published in 1952 a proposed

supplied utilities and facilities, and their occupancy. The

housing ordinance. This provided a prototype on which

2003 International Code Council (ICC) [13,14]

such legislation might be based and has served as the

International Residential Code-One- and Two-Family

basis for countless housing codes enacted in the United

Dwellings (R101.3) states

States since that time. Some municipalities enacted it without

change. Others made revisions by omitting some portions,

“the purpose of this code is to provide minimum

modifying others, and sometimes adding new provisions [9].

requirements to safeguard the public safety, health

and general welfare, through affordability, structural

The APHA ordinance was revised in 1969 and 1971. In 1975,

strength, means of egress, facilities, stability, sanitation,

APHA and the CDC jointly undertook the job of

light and ventilation, energy conservation, safety to

rewriting and updating this model ordinance. The new

fire and property from fire and other hazards

ordinance was entitled the APHA-CDC Recommended

attributed to the built environment.”

Housing Maintenance and Occupancy Ordinance [10]. The

most recent model ordinance was published by APHA in

Critical Requirements of an Effective Housing Program

1986 as Housing and Health: APHA-CDC Recommended

A housing code is limited in its effectiveness by several

Minimum Housing Standards [11]. This new ordinance is

factors. First, if the housing code does not contain standards

one of several model ordinances available to communities

that adequately protect the health and well-being of the

when they are interested in adopting a housing code.

individuals, it cannot be effective. The best-trained

housing inspector, if not armed with an adequate housing

A community should read and consider each element

code, can accomplish little good in the battle against

within the model code to determine its applicability to

urban blight.

their community. A housing code is merely a means to an

end. The end is the eventual elimination of all substandard

A second issue in establishing an effective housing code is

conditions within the home and the neighborhood. This end

the need to establish a baseline of current housing conditions.

cannot be achieved if the community adopts an

A systems approach requires that you establish where you

inadequate housing code.

are, where you are going, and how you plan to achieve your

goals. In using a systems approach, it is essential to know

Objectives

where the program started so that the success or failure of

The Housing Act of 1949 [12] gave new impetus to

various initiatives can be established. Without this

existing local, state, and federal housing programs

information, success cannot be replicated, because you

directed toward eliminating poor housing. In passing

cannot identify the obstacles navigated nor the elements

this legislation, Congress defined a new national

of success. Many initiatives fail because program

objective by declaring that “the general welfare and

administrators are without the necessary proof of success

security of the nation and the health and living

when facing funding shortfalls and budget cuts.

standards of its people...require a decent home and a

suitable living environment for every American family.”

A third factor affecting the quality of housing codes is

This mandate generated an awareness that the quality of

budget. Without adequate funds and personnel, the

housing and residential environment has an enormous

community can expect to lose the battle against urban

influence upon the physical and mental health and the

blight. It is only through a systematic enforcement effort

social well-being of each individual and, in turn, on the

by an adequately sized staff of properly trained inspectors

economic, political, and social conditions in every

that the battle can be won.

community. Consequently, public agencies, units of

government, professional organizations and others sought

A fourth factor is the attitude of the political bodies

ways to ensure that the quality of housing and the

within the area. A properly administered housing program

residential environment did not deteriorate.

will require upgrading substandard housing throughout the

community. Frequently, this results in political pressures

It soon became apparent that ordinances regulating the

being exerted to prevent the enforcement of the code in

supplied utilities and the maintenance and occupancy of

certain areas of the city. If the housing effort is backed

Healthy Housing Reference Manual

3-7

properly by all political elements, blight can be controlled

enabling legislation of the code needed to resolve the

and eventually eliminated within the community. If, however,

problem or there are gaps in jurisdiction.

the housing program is not permitted to choke out the

spreading influence of substandard conditions, urban

Content of a Housing Code

blight will spread like a cancer, engulfing greater and

Although all comprehensive housing codes or ordinances

greater portions of the city. Similarly, an effort directed at

contain a number of common elements, the provisions of

only the most seriously blighted blocks in the city will

communities will usually vary. These variations stem from

upgrade merely those blocks, while the blight spreads

differences in local policies, preferences, and, to a lesser

elsewhere. If urban blight is to be controlled, it must be

extent, needs. They are also influenced by the standards

cut out in its entirety.

set by the related provisions of the diverse building,

electrical, and plumbing codes in use in the municipality.

A fifth element that limits housing programs is whether

they are supported fully by the other departments within

Within any housing code there are generally five features:

the city. Regardless of which city agency administers the

housing program, other city agencies must support the

Definitions of terms used in the code.

activities of the housing program. In addition, great effort

should be expended to obtain the support and

Administrative provisions showing who is

cooperation of the community. This can be accomplished

authorized to administer the code and the basic

through public awareness and public information

methods and procedures that must be followed in

programs, which can result in considerable support or

implementing and enforcing the sections of the

considerable resistance to the efforts of the program.

code. Administrative provisions deal with items

such as reasonable hours of inspections, whether

A sixth limitation is an inadequately or improperly

serving violation notices is required, how to notify

trained inspection staff. Inspectors should be capable of

absentee owners or resident-owners or tenants, how to

evaluating whether a serious or a minor problem exists in

process and conduct hearings, what rules to follow

matters ranging from the structural stability of a building

in processing dwellings alleged to be unfit for

to the health and sanitary aspects of the structure. If they

human habitation, and how to occupy or use

do not have the authority or expertise, they should

dwellings finally declared fit.

develop that expertise or establish effective and efficient

agreements with overlapping agencies to ensure timely

Substantive provisions specifying the various types

and appropriate response.

of health, building, electrical, heating, plumbing,

maintenance, occupancy, and use conditions that

A seventh item that frequently restricts the effectiveness of

constitute violations of the housing code. These

a housing program is the fact that many housing groups

provisions can be and often are grouped into three

fail to do a complete job of evaluating housing

categories: minimum facilities and equipment for

problems. The deterioration of an area may be due to

dwelling units; adequate maintenance of dwellings

factors such as housing affordability, tax rates, or issues

and dwelling units, as well as their facilities and

related to investment cost and return. In many cases, the

equipment; and occupancy conditions of dwellings

inspection effort is restricted to merely evaluating the

and dwelling units.

conditions that exist, with little or no thought given to

why these conditions exist. If a housing effort is to be

Court and penalty sections outlining the basis for

successful, as part of a systems approach, the question of

court action and thepenalty or penalties to which

why the homes deteriorated must be considered. Was

the alleged violator will be subjected if proved

it because of environmental stresses within the

guilty of violating one or more provisions of the code.

neighborhood that need to be eliminated or was it

because of apathy on the part of the occupants? In either

Enabling, conflict, and unconstitutionality

case, if the causative agent is not removed, then the

clauses providing the date a new or amended code

inspector faces an annual problem of maintaining the

will take effect, prevalence of more stringent

quality of that residence. It is only by eliminating the

provision when there is a conflict of two codes,

causes of deterioration that the quality of the

severability of any part of the ordinance that

neighborhood can be maintained. Often the regulatory

might be found unconstitutional, and retention of

authority does not have adequate authority within the

all other parts in full course and effect. In any city

3-8

Housing Regulations

following the format of the APHA-CDC Recommended

deed registration there. If it does not, the advice of the

Housing Maintenance and Occupancy Ordinance

municipal law department should be sought about the next

[10] the housing officer or other supervisor in

steps to follow.

charge of housing inspections will also adopt

appropriate housing rules and regulations from

Due Process Requirements. Every notice, complaint,

time to time to clarify or further refine the

summons, or other type of legal paper concerning alleged

provisions of the ordinance. When rules and

housing code violations in a given dwelling or dwelling

regulations are used, care should be taken that the

unit must be legally served on the proper party to be valid

department is not overburdened with a number of

and to prevent harassment of innocent parties. This might

minor rules and regulations. Similarly, a housing

be the owner, agent, or tenant, as required by the code. It

ordinance that encompasses all rules and regulations

is customary to require that the notice to correct existing

might have difficulty because any amendments to

violations and any subsequent notices or letters be served by

it will require action by the political element of

certified or registered mail with return receipt requested. The

the community. Some housing groups, in

receipt serves as proof of service if the case has to be taken

attempting to obtain amendments to an

to court.

ordinance, have had the entire ordinance thrown

out by the political bodies.

Due process requirements also call for clarity and

specificity with respect to the alleged violations, both in

Administrative Provisions of a Housing Code

the violation notices and the court complaint-summons.

The administrative procedures and powers of the housing

For this reason, special care must be taken to be complete

inspection agency, its supervisors, and its staff are similar to

and accurate in listing the violations and charges. To

other provisions in that all are based on the police power of

illustrate, rather than direct the violator to repair all

the state to legislate for public health and safety. In

windows where needed, the violator should be told

addition, the administrative provisions, and to a lesser

exactly which windows and what repairs are involved.

extent, the court and penalty provisions, outline how the

police power is to be exercised in administering and

The chief limitation on the due process requirement, with

enforcing the code.

respect to service of notices, lies in cases involving

immediate threats to health and safety. In these instances,

Generally, the administrative elements deal with

the inspection agency or its representative may, without

procedures for ensuring that the constitutional doctrines of

notice or hearing, issue an order citing the existence of

reasonableness, equal protection under the law and due

the emergency and requiring that action deemed

process of law are observed. They also must guard against

necessary to meet the emergency be taken.

violation of prohibitions against unlawful search and seizure,

impairment of obligations of contract, and unlawful

In some areas housing courts on the municipal level have

delegation of authority. These factors encompass items of

advocates that assist both plaintiffs and defendants

great importance to housing inspection supervisors such

prepare for the court process or to resolve the issue to

as the inspector’s right of entry, reasonable hours of

avoid court.

inspection, proper service, and the validity of the provisions

of the housing codes they administer.

Hearings and Condemnation Power. The purpose of a

hearing is to give the alleged violator an opportunity to be

Owner of Record. It is essential to file legal actions

heard before further action is taken by the housing inspection

against the true owners of properties in violation of

agency. These hearings may be very informal, involving

housing codes. With the advent of the computer, this is

meetings between a representative of the agency and the

often much easier than in the past. Databases that provide

person ordered to take corrective action. They also may

this information are readily available from many offices of

be formal hearings at which the agency head presides and

local government such as the tax assessment office. The

at which the city and the defendant both are entitled to

method of obtaining the name and address of the legal

be represented by counsel and expert witnesses.

owner of a property in violation varies from place to

place. Ordinarily, a check of the city tax records will

Informal Hearings. A violator may have questions about a

suffice unless there is reason to believe these are not up to

violation notice or the notice may be served at a time

date. In this case, a further check of county or parish

when personal hardship or other factors prevent a violator

records will turn up the legal owner if state law requires

from meeting the terms of the notice. Therefore, many

Healthy Housing Reference Manual

3-9

housing codes provide the opportunity for a hearing at

If they fail to do so, some codes will hold the owner liable

which the violator may discuss questions or problems and

to the purchaser and the inspection agency for violations.

seek additional time or some modification of the order.

Administered in a firm but understanding manner, these

Tickets for Minor Offenses. Denver, Colorado, has used

hearings can serve as invaluable aids in relieving needless

minimal financial fines to prod minor violators and first

fears of those involved, in showing how the inspection

offenders into correcting violations without the city

program is designed to help them and in winning their

resorting to court action. There are mixed views about

voluntary compliance.

this technique because it is akin to formal police action.

Nevertheless, the action may stimulate compliance and

Formal Hearings. Formal hearings are often quasijudicial

reduce the amount of court action needed to achieve it.

hearings (even though the prevailing court rules of

evidence do not always apply) from which an appeal may

Forms and Form Letters. A fairly typical set of forms and

be taken to court. All witnesses must therefore be sworn

form letters are described below. It should be stressed that

in, and a record of the proceedings must be made. The

inspection forms to be used for legal notices must satisfy

formal hearing is used chiefly as the basis for determining

legal standards of the code, be meaningful to the owner

whether a dwelling is fit for human habitation,

and sufficiently explicit about the extent and location of

occupancy, or use. In the event it is proved unfit, the

particular defects, be adaptable to statistical compilation

building is condemned and the owner is given a

for the governing body reports, and be written in a manner

designated amount of time either to rehabilitate it

that will facilitate clerical and other administrative usage.

completely or to demolish it. Where local funds are

available, a municipality may demolish the building and

The Daily Report Form. This form gives the inspection

place a lien against the property to cover demolition costs

agency an accurate basis for reporting, evaluating, and, if

if the owner fails to obey the order within the time

necessary, improving the productivity and performance of

specified. This type of condemnation hearing is a very

its inspectors.

effective means of stimulating prompt and appropriate

corrective action when it is administered fairly and firmly.

Complaint Form. This form helps obtain full information

from the complainant and thus makes the relative

Procedures for Coping With Common Problems. Several

seriousness of the problem clear and reduces the number

states and local communities have developed innovative

of crank complaints.

ways to resolve code violation issues.

No-entry Notice. This notice advises occupants or owners

Limitation of Occupancy Notification. This technique

that an inspector was there and that they must return a

was pioneered in Wilmington, Delaware. It makes it

call to the inspector.

mandatory for property owners in the community to

obtain a legal notice from the housing inspection agency

Inspection Report Form. This is the most important form

specifying the maximum number of persons that may

in an agency. It comes in countless varieties, but if designed

occupy each of their properties. It also requires these owners

properly, it will ensure more productivity and more

to have a residence, place of business, or an agent for their

thoroughness by the inspectors, reduce the time spent in

properties within the community. The agent should be

writing reports, locate all violations correctly, and reduce

empowered to take remedial action on any of the

the time required for typing violation notices. Forms may

properties found in violation. In addition, if the property

vary widely in sophistication from a very simple form to

is sold, the new owner must obtain a new Limitation of

one whose components are identified by number for use

Occupancy Notification.

in processing the case by automation. Some forms are a

combined inspection report and notice form in triplicate so

Request for Inspections. Several states permit their

that the first page can be used as the notice of violation, the

municipalities to offer a request for inspection service. For

second as the office record, and the third as the guide for

a fee, the housing inspector will inspect a property for

reinspection. A covering form letter notifies the violator of

violations of the housing code before its sale so that the

the time allowed to correct the conditions listed in the

buyer can learn its condition in advance. Many states and

report form.

localities now require owners to notify prospective

purchasers of any outstanding notice of health risk or

Violation Notice. This is the legal notice that housing

violations they have against their property before the sale.

code violations exist and must be corrected within the

3-10

Housing Regulations

indicated amount of time. The notice may be in the form

Dwelling units should have provisions for preparing at least

of a letter that includes the alleged violations or has a

one regularly cooked meal per day. Minimum equipment

copy of these attached. It may be a standard notice form,

should include a kitchen sink in good working condition

or it may be a combined report-notice. Regardless of the

and properly connected to the water supply system

type of notice used, it should make the location and

approved by the appropriate authority. It should provide,

nature of all violations clear and specify the exact section

at all times, an adequate amount of heated and unheated

of the code that covers each one. The notice must advise

running water under pressure and should be connected to

violators of their right to a hearing. It should also indicate

a sewer system approved by the appropriate authority.

that the violator has a right to be represented by counsel

Cabinets or shelves, or both, for storing eating, drinking,

and that failure to obtain counsel will not be accepted as

and cooking utensils and food should be provided. These

grounds for postponing a hearing or court case.

surfaces should be of sound construction and made of

material that is easy to clean and that will not have a toxic

Hearing Forms. These should include a form letter

or deleterious effect on food.

notifying the violator of the date and time set for the hearing,

a standard summary sheet on which the supervisor can

In addition, a stove and refrigerator should be provided.

record the facts presented at an informal hearing, and a

Within every dwelling there should be a room that affords

hearing-decision letter for notifying all concerned of the

privacy and is equipped with a flush toilet in good working

hearing results. The latter should include the names of the

condition.

violator, inspector, law department, and any other city

official or agency that may be involved in the case.

Within the vicinity of the flush toilet, a sink should be

provided. In no case should a kitchen sink substitute as a

Reinspection Form Letters or Notices. These have the

lavatory sink. In addition, within each dwelling unit there

same characteristics as violation notices except that they

should be, within a room that affords privacy, either a bathtub

cover the follow-up orders given to the violator who has

or shower or both, in good working condition. Both the

failed to comply with the original notice within the time

lavatory sink and the bathtub or shower or both should be

specified. Some agencies may use two or three types of

equipped with an adequate amount of heated and

these form letters to accommodate different degrees of

unheated water under pressure. Each should be connected

response by the violator. Whether one or several are used,

to an approved sewer system.

standardization of these letters or notices will expedite the

processing of cases.

Within each dwelling unit two or more means of egress should

be provided to safe and open space at ground level. Provisions

Court Complaint and Summons Forms. These forms

should be incorporated within the housing code to meet the

advise alleged violators of the charges against them and

safety requirements of the state and community involved. The

summon them to appear in court at the specified time

housing code should spell out minimum standards for lighting

and place. It is essential that the housing inspection

and ventilation within each room in the structure. In addition,

agency work closely with the municipal law department

minimum thermal standards should be provided.

in preparing these forms so that each is done in exact

Although most codes merely provide the requirement of a

accord with the rules of court procedure in the relevant

given temperature at a given height above floor level, the

state and community.

community should give consideration to the use of

effective temperatures. The effective temperature is a means of

Court Action Record Form. This form provides an accurate

incorporating not only absolute temperature in degrees, but

running record of the inspection agency’s court actions and

also humidity and air movement, giving a better indication of

their results.

the comfort index of a room.

Substantive Provisions of a Housing Code

The code should provide that no person shall occupy or

A housing code is the primary tool of the housing

let for occupancy any dwelling or dwelling units that do

inspector. The code spells out what the inspector may or

not comply with stated requirements. Generally, these

may not do. An effort to improve housing conditions can be

requirements specify that the foundation, roof, exterior walls,

no better than the code allows. The substantive provisions of

doors, window space and windows of the structure be

the code specify the minimal housing conditions acceptable

sound and in good repair; that it be moisture-free,

to the community that developed them.

watertight and reasonably weather tight and that all

structural surfaces be sound and in good repair.

Healthy Housing Reference Manual

3-11

HUD defines a multifamily dwelling unit as one that contains

References

four or more dwelling units in a single structure. A

Hammurabi’s Code of Laws. Translated by L.W.

dwelling unit is further defined as a single unit of

King. Available from URL:

residence for a family of one or more persons in which

http://eawc.evansville.edu/anthology/hammurabi.htm.

sleeping accommodations are provided but toileting or

cooking facilities are shared by the occupants.

Claghorn KH. The foreign immigrant in New

York City. Reports of the Industrial Commission,

Building Codes

Volume XV. Washington, DC: US Government

Building codes define what materials and methods are

Printing Office; 1901.p. 465-92. Available from

tobe used in the construction of various buildings. Model

URL: http://tenant.net/Community/LES/clag2.html.

building codes have been published by various trade

organizations such as the Southern Building Code Congress

Riis J. How the other half lives—studies among

International (SBCCI), Building Officials and Code

the tenements of New York. New York: Charles

Administrators (BOCA), and the International Conference of

Scriber’s Sons; 1890. Available from URL:

Building Officials (ICBO). Each of these groups

http://www.bartleby.com/208/.

published a model building code that was widely used or

adapted regionally in the United States. BOCA national

New York City Department of City Planning. New

codes were used mostly in eastern and Great Lakes states,

York City zoning: zoning history. New York City:

ICBO uniform codes in western and Midwest states, and

New York City Department of City Planning; no

SBCCI standard codes in southern states. As a result, the

date. Available from URL:

construction industry often faced the challenge, and cost,

http://www.nyc.gov/html/dcp/html/

of building to different codes in different areas of the country.

zone/zonehis.html.

In 1994, BOCA, ICBO, and SBCCI created the

New York State Multiple Dwelling Law: chapter

International Code Council (ICC) to develop a single set of

713 of the Laws of 1929, as amended. Available

comprehensive, coordinated model construction codes that

from URL: http://tenant.net/Other_Laws/

could be used throughout the United States and around

MDL/mdltoc.html.

the world. The first I-Code published was the

International Plumbing Code in 1995. By 2000, a

Understanding Fannie Mae: our history.

complete family of I-Codes was available, including the

Washington, DC: Fannie Mae; 2005. Available

International Building Code. The ICC Performance Code for

from URL: http://www. fanniemae.com/aboutfm/

Buildings and Facilities joined the I-Code family in 2001.

understanding/history.jhtml?p=About+Fannie+

Mae&s=Understanding+Fannie+

On February 1, 2003, the three organizations (BOCA,

Mae&t=Our+History.

SBCCI, and ICBO) were consolidated into the ICC

[13,14]. According to ICC Board president, Paul E. Myers,

Paulson PB. Protecting zoning laws. Atlanta:

North Buckhead Civic Association; 2000 18 Mar.

“The ICC International Codes (I Codes) combine

Available from URL:

the strengths of the regional codes without regional

http://www.nbca.org/TAP_AJC_3-18.htm.

limitations. The ICC is a nonprofit organization

dedicated to developing a single set of comprehensive

Municipal Code Corporation. Municipal building

and coordinated national codes to make compliance

codes (online library). Tallahassee, FL: Municipal

easier and more cost-effective. I Codes respond to the

Code Corporation. Available from URL:

needs of the construction industry and public safety.

http://www.municode.com/resources/

A single set of codes has strong support from

online_codes.asp.

government, code enforcement officials, fire officials,

architects, engineers, builders, developers, and

American Public Health Association. Housing

building owners and managers.”

ordinance. Am J Public Health 1952

Jan;42(1):76-7.

10. US Public Health Service. APHA-CDC

recommended housing maintenance and occupancy

3-12

Housing Regulations

ordinance. Atlanta: US Department of Health and

US Department of Housing and Urban Development. Final

Human Services; 1975.

report of HUD review of model building codes.

Washington, DC: US Department of Housing and Urban

11. American Public Health Association. Housing

Development; no date. Available from URL:

and health: APHA-CDC recommended minimum

http://www.hud.gov/offices/fheo/disabilities/

housing standards. Washington, DC: American

modelcodes/chapter5.html.

Public Health Association; 1986.

12. Lang RE, Sohmer RR, editors. Legacy of the

Housing Act of 1949: The past, present, and

future of federal housing and urban policy.

Housing Policy Debate 2000;11(2): 291-7.

Available from URL:

http://www.fanniemaefoundation.org/programs/

hpd/pdf/ hpd_ 1102_edintro.pdf.

13. International Code Council. International

residential code 2003. Country Club Hills, IL:

ICC; 2003.

14. International Code Council. International

building code 2003. Country Club Hills, IL:

ICC; 2003.

Additional Sources of Information

American Planning Association. Available from URL:

http://www.planning.org/.

Arendt R. “Open Space” zoning: what it is and why it

works. Planners Commission Journal 1992. Available

from URL: http://www.plannersweb.com/articles/are015.html.

Bookmark, Inc. Available from URL: http://www.

bookmarki.com.

International Code Council. Available from URL:

http://www.iccsafe.org.

Rosenberg M. Zoning: residential, commercial, or

industrial? New York: About, Inc.; no date. Available

from URL: http://geography.about.com/library/weekly/

aa072801a.htm?iam=sherlock_abc/.

US Department of Energy, Land Use Planning. Smart

Communities Network. Washington, DC: US Department

of Energy; no date. Available from URL: http://www.

smartcommunities.ncat.org/landuse/luintro.shtml.

US Department of Housing and Urban Development.

Available from URL: http://www.hud.gov/.

Healthy Housing Reference Manual

3-13

Chapter 4: Disease Vectors and Pests

“Sometimes poor housing is a shorthand way of describing

This chapter deals with disease vectors and pests as

living conditions of poor people. The poor include the aged,

factors related to the health of households.

deprived, ethnic minority groups, the infirmed, and families

headed by unemployed women. In other words, the people

Disease Vectors and Pests

most at risk for illness often live in inferior housing.

Integrated pest management (IPM) techniques are

Therefore, it is a matter of conjecture whether many people

necessary to reduce the number of pests that threaten

live in poor housing because they are sick or are sick because

human health and property. This systems approach to

they live in poor housing.”

the problem relies on more than one technique to reduce

or eliminate pests. It can be visualized best as concentric

Carter L. Marshall, M.D.

rings of protection that reduce the need for the most

Dynamics of Health and Disease

risky and dangerous options of control and the potential

Appleton, Century Crofts 1972

for pests to evolve and develop. It typically involves using

some or all of the following steps:

Introduction

The most immediate and obvious link between housing and

• monitoring, identifying, and determining the

health involves exposure to biologic, chemical, and

level of threat from pests;

physical agents that can affect the health and safety of the

occupants of the home. Conditions such as childhood lead

• making the environment hostile to pests;

poisoning and respiratory illnesses caused by exposure to

radon, asbestos, tobacco smoke, and other pollutants are

• building the pests out by using pest-proof building

increasingly well understood and documented. However,

materials;

even 50 years ago, public health officials understood that

housing conditions were linked to a broader pattern of

• eliminating food sources, hiding areas, and

community health. For example, in 1949, the Surgeon

other pest attractants;

General released a report comparing several health status

indicators among six cities having slums. The publication

• using traps and other physical elimination devices; and

reported that:

• when necessary, selecting appropriate poisons

• the rate of deaths from communicable disease in

for identified pests.

these areas was the same as it was for the rest of

the country 50 years ago (i.e., around 1900);

The above actions are discussed in more detail in the

following section on the four basic strategies for

• most of the tuberculosis cases came from 25% of

controlling rodents.

the population of these cities; and

Most homeowners have encountered a problem with

• the infant mortality rate was five times higher

rodents, cockroaches, fleas, flies, termites, or fire ants.

than in the rest of the country, approximately

These pests destroy property or carry disease, or both,

equal to what it was 50 years ago.

and can be a problem for rich and poor alike.

Housing-related health concerns include asthma episodes

Rodents

triggered by exposure to dust mites, cockroaches, pets,

Rodents destroy property, spread disease, compete for human

and rodents. The existence of cockroaches, rats, and mice

food sources, and are aesthetically displeasing. Rodent-

mean that they can also be vectors for significant

associated diseases affecting humans include plague, murine

problems that affect health and well-being. They are

typhus, leptospirosis, rickettsialpox, and rat-bite fever. The

capable of transmitting diseases to humans. According to

three primary rodents of concern to the homeowner are the

a 1997 American Housing Survey, rats and mice infested

Norway rat (Rattus norvegicus), roof rat (Rattus rattus), and the

2.7 million of 97 million housing units. A CDC-sponsored

house mouse (Mus musculus). The term “commensal” is

survey of two major American cities documented that

applied to these rodents, meaning they live at people’s expense.

nearly 50% of the premises were infected with rats and mice.

The physical traits of each are demonstrated in Figure 4.1.

Healthy Housing Reference Manual

4-1

Figure 4.1. Field Identification of Domestic Rodents [2]

Barnett [1] notes that the house mouse is abundant

The roof rat (Figure 4.3) is a slender, graceful, and very

throughout the United States. The Norway rat

agile climber. The roof rat prefers to live aboveground:

(Figure 4.2) is found throughout the temperate regions

indoors in attics, between floors, in walls, or in enclosed

of the world, including the United States. The roof rat

spaces; and outdoors in trees and dense vine growth.

is found mainly in the South, across the entire nation to

Contrasted with the

the Pacific coast. As a group, rodents have certain

roof rat, the Norway rat

behavioral characteristics that are helpful in

is at home below the

understanding them. They are perceptive to touch,

ground, living in a

with sensitive whiskers and guard hairs on their bodies.

burrow. The house

Thus, they favor running along walls and between

mouse commonly is

objects that allow them

found living in human

constant contact with

quarters, as suggested by

vertical surfaces. They are

its name. Signs indicative

Figure 4.3. Roof Rat [4]

known to have poor

of the presence of

eyesight and are alleged to

rodents—aside from seeing live or dead rats and hearing

be colorblind.

rats—are rodent droppings, runways, and tracks

Contrastingly, they have an

(Figure 4.4). Other signs include nests, gnawings, food

extremely sharp sense of

scraps, rat hair, urine spots, and rat body odors. Note

smell and a keen sense of

that waste droppings from rodents are often confused

taste. The word rodent is

with cockroach egg packets, which are smooth,

derived from the Latin verb

segmented, and considerably smaller than a mouse dropping.

rodere, meaning “to gnaw.”

Figure 4.2. Norway Rat [3]

According to the Military Pest Management Handbook

The gnawing tendency leads to structural damage to

(MPMH) [2], rats and mice are very suspicious of any

buildings and initiates fires when insulation is chewed

new objects or food found in their surroundings. This

from electrical wires. Rodents will gnaw to gain entrance

characteristic is one reason rodents can survive in dangerous

and to obtain food.

environments. This avoidance reaction accounts for

prebaiting (baiting without poisoning) in control programs.

4-2

Disease Vectors and Pests

built or modified in a way that prevents easy access by

rodents. Tactics for rodent exclusion include building or

covering doors and windows with metal. Rats can gnaw

through wooden doors and windows in a very short time

to gain entrance. All holes in a building’s exterior should

be sealed. Rats are capable of enlarging openings in

masonry, especially if the mortar or brick is of poor

quality. All openings more than ¾-inch wide should be

closed, especially around pipes and conduits. Cracks

around doors, gratings, windows, and other such

openings should be covered if they are less than 4 feet

above the ground or accessible from ledges, pipes, or

wires (Figure 4.5).

Additional tactics include using proper materials for rat

proofing. For example, sheet metal of at least 26-gauge,

¼-inch or ½-inch hardware cloth, and cement are all

suitable rat-resistant materials. However, ½-inch

hardware cloth has little value against house mice. Tight

fittings and self-closing doors should be constructed.

Rodent runways can be behind double walls; therefore,

spaces between walls and floor-supporting beams should

be blocked with fire stops. A proper rodent-proofing

Figure 4.4. Signs of Rodent Infestation [2]

strategy must bear in mind that rats can routinely jump

2 feet vertically, dig 4 feet or more to get under a

Initially, rats or mice begin by taking only small amounts

foundation, climb rough walls or smooth pipes up to

of food. If the animal becomes ill from a sublethal dose of

3 inches in diameter, and routinely travel on electric

poison, its avoidance reaction is strengthened, and a

or telephone wires.

poisoning program becomes extremely difficult to

complete. If rodents are hungry or exposed to an environment

The first three strategies—good sanitation techniques,

where new objects and food are commonly found, such

habitat denial, and rat proofing—should be used initially

as a dump, their avoidance reaction may not be as strong;

in any rodent management program. Should they fail, the

in extreme cases of hunger, it may even be absent.

fourth strategy is a killing program, which can vary from

a family cat to the professional application of

The first of four basic strategies for controlling rodents is

rodenticides. Cats can be effective against mice, but

to eliminate food sources. To accomplish this, it is

typically are not useful against a rat infestation. Over-the-

imperative for the homeowner or occupant to do a good

counter rodenticides can be purchased and used by the

job of solid waste management. This requires proper

homeowner or occupant. These typically are in the red

storing, collecting, and disposing of refuse.

squill or warfarin groups.

The second strategy is to eliminate breeding and nesting

A more effective alternative is trapping. There are a

places. This is accomplished by removing rubbish from

variety of devices to choose from when trapping rats or

near the home, including excess lumber, firewood, and

mice. The two main groups of rat and mouse traps are

similar materials. These items should be stored above

live traps (Figure 4.6) and kill traps (Figure 4.7). Traps

ground with 18 inches of clearance below them. This

usually are placed along walls, near runways and burrows,

height does not provide a habitat for rats, which have a

and in other areas. Bait is often used to attract the

propensity for dark, moist places in which to burrow.

rodents to the trap. To be effective, traps must be

Wood should not be stored directly on the ground, and

monitored and emptied or removed quickly. If a rat

trash and similar rubbish should be eliminated.

caught in a trap is left there, other rats may avoid the traps.

A trapping strategy also may include using live traps to

The third strategy is to construct buildings and other

remove these vermin.

structures using rat-proofing methods. MPMH notes

that it is much easier to manage rodents if a structure is

Healthy Housing Reference Manual

4-3

Figure 4.7. Kill Traps for Rats [2]

Cockroaches

Cockroaches have become well adapted to living with and

near humans, and their hardiness is legendary. In light of

these facts, cockroach control may become a homeowner’s

most difficult task because of the time and special

knowledge it often involves. The cockroach is considered

an allergen source and an asthma trigger for residents.

Although little evidence exists to link the cockroach to

specific disease outbreaks, it has bee demonstrated to

carry Salmonella typhimurium, Entamoeba histolytica, and

the poliomyelitis virus. In addition, Kamble and Keith [6]

note that most cockroaches produce a repulsive odor that

can be detected in infested areas. The sight of cockroaches

can cause considerable psychologic or emotional distress

in some individuals. They do not bite, but they do have

heavy leg spines that may scratch.

According to MPMH [2], there are 55 species of

cockroaches in the United States. As a group, they tend to

prefer a moist, warm habitat because most are tropical in

Figure 4.5. Rodent Prevention [2]

origin. Although some tropical cockroaches feed only on

vegetation, cockroaches of public health interest tend to

live in structures and are customarily scavengers.

Cockroaches will eat a great variety of materials, including

cheese and bakery products, but they are especially fond

of starchy materials, sweet substances, and meat products.

Cockroaches are primarily nocturnal. Daytime sightings

may indicate potentially heavy infestations. They tend to

hide in cracks and crevices and can move freely from

room to room or adjoining housing units via wall spaces,

plumbing, and other utility installations. Entry into

homes is often accomplished through food and beverage

boxes, grocery sacks, animal food, and household goods

Figure 4.6. Live Traps for Rats [5]

carried into the home. The species of public health

4-4

Disease Vectors and Pests

interest that commonly inhabit human dwellings

(Figures 4.8-4.13) include the following: German

cockroach (Blattella germanica); American cockroach

(Periplaneta americana); Oriental cockroach (Blatta

orientalis); brown-banded cockroach (Supella longipalpa);

Australian cockroach (Periplaneta australasiae); smoky-

brown cockroach (Periplaneta fuliginosa); and brown

cockroach (Periplaneta brunnea).

Four management strategies exist for controlling

cockroaches. The first is prevention. This strategy

includes inspecting items being carried into the home

Figure 4.10. Oriental Cockroaches, Various Stages and Ages [7]

and sealing cracks and crevices in kitchens, bathrooms,

exterior doors, and windows. Structural modifications

would include weather stripping and pipe collars. The

second strategy is sanitation. This denies cockroaches food,

water, and shelter. These efforts include quickly cleaning

food particles from shelving and floors; timely washing of

dinnerware; and routine cleaning under refrigerators,

stoves, furniture, and similar areas. If pets are fed indoors,

pet food should be stored in tight containers and not left

in bowls overnight. Litter boxes should be cleaned

routinely. Access should be denied to water sources by

fixing leaking plumbing, drains, sink traps, and purging

clutter, such as papers and soiled clothing and rags. The

Figure 4.11. German Cockroaches, Various Stages and Ages [7]

third strategy is trapping. Commercially available cockroach

Figure 4.8. American, Oriental, German, and Brown- banded

Figure 4.12. Brown-banded Cockroaches, Various Stages and

Cockroaches [7]

Ages [7]

Figure 4.13. Wood Cockroach, Adult Male [7]

Figure 4.9. American Cockroaches, Various Stages and Ages [7]

Healthy Housing Reference Manual

4-5

traps can be used to capture roaches and serve as a

monitoring device. The most effective trap placement is

against vertical surfaces, primarily corners, and under

sinks, in cabinets, basements, and floor drains. The fourth

strategy is chemical control. The use of chemicals

typically indicates that the other three strategies have been

applied incorrectly. Numerous insecticides are available

and appropriate information is obtainable from EPA.

Fleas

The most important fleas as disease vectors are those that

carry murine typhus and bubonic plague. In addition,

fleas serve as intermediate hosts for some species of dog and

rodent tapeworms that occasionally infest people. They also

may act as intermediate hosts of filarial worms

(heartworms) in dogs. In the United States, the most

important disease related to fleas is the bubonic plague.

This is primarily a concern of residents in the southwestern

and western parts of the country (Figure 4.14).

Of approximately 2,000 species of flea, the most common

flea infesting both dogs and cats is the cat flea

Ctenocephalides felis. Although numerous animals, both

wild and domestic, can have flea infestations, it is from

the exposure of domestic dogs and cats that most

homeowners inherit flea infestation problems. According to

MPMH [2], fleas are wingless insects varying from 1 to

8½ millimeters (mm) long, averaging 2 to 4 mm, and

feed through a siphon or tube. They are narrow and

Figure 4.14. Reported Human Plague Cases (1970-1997) [8]

compressed laterally with backwardly directed spines,

which adapt them for moving between the hairs and

feathers of mammals and birds. They have long, powerful

legs adapted for jumping. Both sexes feed on blood, and

the female requires a blood meal before she can produce

viable eggs. Fleas tend to be host-specific, thus feeding on

only one type of host. However, they will infest other

species in the absence of the favored host. They are found

in relative abundance on animals that live in burrows and

sheltered nests, while mammals and birds with no

permanent nests or that are exposed to the elements tend

to have light infestations.

MPMH [2] notes that fleas undergo complete metamorphosis

(egg, larva, pupa, and adult). The time it takes to

complete the life cycle from egg to adult varies according

to the species, temperature, humidity, and food

availability. Under favorable conditions, some species can

complete a generation in as little as 2 or 3 weeks.

Figure 4.15 shows the life cycle of the flea.

Figure 4.15. Flea Life Cycle [2]

4-6

Disease Vectors and Pests

Flea eggs usually are laid singly or in small groups among

• Reapplication to heavily infested source points in

the feathers or hairs of the host or in a nest. They are

the home and the yard may be needed to elimi-

often laid in carpets of living quarters if the primary host

nate pre-emerged adults.

is a household pet. Eggs are smooth, spherical to oval,

light colored, and large enough to be seen with the naked

Flies

eye. An adult female flea can produce up to 2,000 eggs in

The historical attitude of Western society toward flies has

a lifetime. Flea larvae are small (2 to 5 mm), white, and

been one of aesthetic disdain. The public health view is to

wormlike with a darker head and a body that will appear

classify flies as biting or nonbiting. Biting flies include

brown if they have fed on flea feces. This stage is mobile

sand flies, horseflies, and deerflies. Nonbiting flies include

and will move away from light, thus they typically will be

houseflies, bottleflies, and screwworm flies. The latter

found in shaded areas or under furniture. In 5 to 12 days,

group is often referred to as synanthropic because of their

they complete the three larval stages; however, this may

close association with humans. In general, the presence of

take several months depending on environmental

flies is a sign of poor sanitation. The primary concern of

conditions. The larvae, after completing development,

most homeowners is nonbiting flies.

spin a cocoon of silk encrusted with granules of sand or

According to

various types of debris to form the pupal stage. The pupal

MPMH [2], the

stage can be dormant for 140 to 170 days. In some areas

housefly (Musca

of the country, fleas can survive through the winter. The

domestica) (Figure

pupae, after development, are stimulated to emerge as

4.16) is one of the

adults by movement, pressure, or heat. The pupal form of

most widely

the flea is resistant to insecticides. An initial treatment,

distributed insects,

while killing egg, larvae, and adult forms, will not kill the

occurring

pupae. Therefore, a reapplication will often be necessary.

throughout the

The adult forms are usually ready to feed about 24 hours

United States, and

Figure 4.16. Housefly [Musca domestica] [9]

after they emerge from the cocoon and will begin to feed

is usually the

within 10 seconds of landing on a host. Mating usually

predominant fly species in homes and restaurants. M.

follows the initial blood meal, and egg production is

domestica is also the most prominent human-associated

initiated 24 to 48 hours after consuming a blood meal.

(synanthropic) fly in the southern United States. Because

The adult flea lives approximately 100 days, depending

of its close association with people, its abundance, and its

on environmental conditions.

ability to transmit disease, it is considered a greater threat

to human welfare than any other species of nonbiting fly.

Following are some guidelines for controlling fleas:

Each housefly can easily carry more than 1 million bacteria

on its body. Some of the disease-causing agents transmitted

• The most important principle in a total flea control

by houseflies to humans are Shigella spp. (dysentery and

program is simultaneously treating all pets and their

diarrhea = shigellosis), Salmonella spp. (typhoid fever),

environments (indoor and outdoor).

Escherichia coli, (traveler’s diarrhea), and Vibrio cholera

(cholera). Sometimes these organisms are carried on the

• Before using insecticides, thoroughly clean the

fly’s tarsi or body hairs, and frequently they are

environment, removing as many fleas as possible,

regurgitated onto food when the fly attempts to liquefy it

regardless of the form. This would include indoor

for ingestion.

vacuuming and carpet steam cleaning. Special

attention should be paid to source points where pets

The fly life cycle is similar across the synanthropic group.

spend most of their time.

MPMH [2] notes that the egg and larval stages develop in

animal and vegetable refuse. Favorite breeding sites

• Outdoor cleanup should include mowing, yard raking,

include garbage, animal manure, spilled animal feed, and soil

and removing organic debris from flowerbeds and

contaminated with organic matter. Favorable

under bushes.

environmental conditions will result in the eggs hatching

in 24 hours or less. Normally, a female fly will produce

• Insecticide should be applied to the indoor and

500 to 600 eggs during her lifetime.

outdoor environments and to the pet.

The creamy, white larvae (maggots) are about ½-inch

long when mature and move within the breeding material

Healthy Housing Reference Manual

4-7

to maintain optimum temperature and moisture

or other protected sites, but will not reproduce during

conditions. This stage lasts an average of 4 to 7 days in

this time. Blowflies breed most commonly on decayed

warm weather. The larvae move to dry parts of the

carcasses (e.g., dead squirrels, rodents, birds) and in

breeding medium or move out of it onto the soil or

droppings of dogs or other pets during the summer; thus,

sheltered places under debris to pupate, with this stage

removal of these sources is imperative. Small animals, on

usually lasting 4 to 5 days. When the pupal stage is

occasion, may die inside walls or under the crawl space of

accomplished, the adult fly exits the puparium, dries, hardens,

a house. A week or two later, blowflies or maggots may

and flies away to feed, with mating occurring soon after

appear. The adult blowfly is also attracted to gas leaks.

emergence. Figure 4.17 demonstrates the typical fly life

cycle.

Termites

According to Gold et al. [11], subterranean termites are

The control of the housefly is hinged on good sanitation

the most destructive insect pests of wood in the United

(denying food sources and breeding sites to the fly). This

States, causing more than $2 billion in damage each year.

includes the proper disposal of food wastes by placing

Annually, this is more property damage than that caused

garbage in cans with close-fitting lids. Cans need to be

by fire and windstorms combined. In the natural world,

periodically washed and cleaned to remove food debris.

these insects are beneficial because they break down dead

The disposal of garbage in properly operated sanitary

trees and other wood materials that would otherwise

landfills is paramount to fly control.

accumulate. This biomass breakdown is recycled to the

soil as humus. MPMH [2], on the other hand, notes that

The presence of adult flies can be addressed in various

these insects can damage a building so severely it may

ways. Outside methods include limited placement of

have to be replaced. Termites consume wood and other

common mercury vapor lamps that tend to attract flies.

cellulose products, such as paper, cardboard, and

Less-attractive sodium vapor lamps should be used near

fiberboard. They will also destroy structural timbers,

the home. Self-closing doors in the home will deny

pallets, crates, furniture, and other wood products. In

entrance, as will the use of proper-fitting and well-

addition, they will damage many materials they do not

maintained screening on doors and windows.

normally eat as they search for food. The tunneling efforts

of subterranean termites can penetrate lead- and plastic-

Larger flies use homes for shelter from the cold, but do

covered electric cable and cause electrical system failure.

not reproduce inside the home. Caulking entry points

In nature, termites may live for years in tree stumps or

and using fly swatters is effective and much safer than the

lumber beneath concrete buildings before they penetrate

use of most pesticides. Insecticide “bombs” can be used in

hairline cracks in floors and walls, as well as expansion

attics and other rooms that can be isolated from the rest

joints, to search for food in areas such as interior door

of the house. However, these should be applied to areas

frames and immobile furniture. Termite management costs to

away from food, where flies rest.

homeowners are exceeded only by cockroach control costs.

The blowfly is a fairly large, metallic green, gray, blue,

Lyon [12] notes that termites are frequently mistaken by

bronze, or black fly. They may spend the winter in homes

the homeowner as ants and often are referred to

erroneously as white ants. Typical signs of termite

infestations occur in March through June and in

September and October. Swarming is an event where a

group of adult males and female reproductives leave the

nest to establish a new colony. If the emergence happens

inside a building, flying termites may constitute a

considerable nuisance. These pests can be collected with a

vacuum cleaner or otherwise disposed of without using

pesticides. Each homeowner should be aware of the

following signs of termite infestation:

• Pencil-thin mud tubes extending over the inside

and outside surfaces of foundation walls, piers,

sills, joists, and similar areas (Figures 4.18 and 4.19).

Figure 4.17. Life Cycle of the Fly [10]

4-8

Disease Vectors and Pests

• Presence of winged termites or their shed wings

hind pair is much shorter than the front. Additionally,

on windowsills and along the edges of floors.

ants typically have a narrow waist, with the abdomen

connected to the thorax by a thin petiole. Termites do

• Damaged wood hollowed out along the grain and

not have a narrow or pinched waist. Figure 4.20a and b

lined with bits of mud or soil. According to Oi

demonstrates the differences between the ant and termite.

et al. [15], termite tubes and nests are made of

Entomologists refer to winged ants and termites as alates.

mud and carton. Carton is composed of partially

chewed wood, feces, and soil packed together.

Figure 4.21 shows the life cycle of the termite. In each

Tubes maintain the high humidity required for

colony, there are three castes or forms of individuals

survival, protect termites from predators, and

known as reproductives, workers, and soldiers. According

allow termites to move from one spot to another.

to Lyon [12], the reproductives can be winged or

wingless, with the latter found in colonies to serve as

Differentiating the ant from the dark brown or black

replacements for the primary reproductives. The primary

termite reproductives can be accomplished by noting the

reproductives (alates) vary in color from pale yellow-

respective wings and body shape. MPMH [2] states that a

brown to coal black, are ½-inch to 3/8-inch in length, are

termite has four wings of about equal length and that the

flattened dorsa-ventrally, and have pale or smoke-gray to

wings are nearly twice as long as the body. By comparison, ant

brown wings. The secondary reproductives have short

wings that are only a little longer than the body and the

wing buds and are white to cream colored. The workers

are the same size as the primary reproductives and are

white to grayish-white, with a yellow-brown head, and

are wingless. In addition, the soldiers resemble workers,

Figure 4.18. Termite Tube Extending from Ground to Wall [Red

Figure 4.20a. Ant (Elbowed Antennae: Fore Wings Larger Than Hind;

Arrows] [13]

Constricted Waist) [16]

Figure 4.20b. Termite (Beaded Antennae; All Wings Equal) [16]

in that they are wingless, but soldiers have large,

rectangular, yellowish, and brown heads with large jaws.

MPMH [2] states there are five families of termites found

in the world, with four of them occurring in the United

States. The families in the United States are

Figure 4.19. Termite Mud Shelter Tube Constructed Over a Brick

Hodotermitidae (rotten-wood termites), Kalotermitidae

Foundation [14]

(dry-wood termites), Rhinotermitidae (subterranean

Healthy Housing Reference Manual

4-9

Dry-wood termites (Cryptotermes spp.) live entirely in

moderately to extremely dry wood. They require contact

with neither the soil nor any other moisture source and

may invade isolated pieces of furniture, fence posts,

utility poles, firewood, and structures. Dry-wood termite

colonies are not as large as other species in the United

States, so they can occupy small wooden articles, which

are one way these insects spread to different locations.

They are of major economic importance in southern

California, Arizona, and along the Gulf Coast. The West

Indian dry-wood termite is a problem in Puerto Rico, the

U.S. Virgin Islands, Hawaii, parts of Florida and

Louisiana, and a number of U.S. Pacific Island territories.

Dry-wood termites are slightly larger than most other

Figure 4.21. Life Cycle of the Subterranean Termite [17]

species, ranging from ½ inch to 5/8 inch long, and are

generally lighter in color.

termites) and Termitidae (desert termites). Subterranean

termites typically work in wood aboveground, but must

Damp-wood termites do not need contact with damp

have direct contact with the ground to obtain moisture.

ground like subterranean termites do, but they do require

Nonsubterranean termites colonize above the ground and

higher moisture content in wood. However, once

feed on cellulose; however, their life cycles and methods

established, these termites may extend into slightly drier wood.

of attack, and consequently methods of control, are quite

different. Nonsubterranean termites in the United States

Termites of minor importance are the tree-nesting groups.

are commonly called drywood termites.

The nests of these termites are found in trees, posts, and,

occasionally, buildings. Their aboveground nests are

In the United States, according to MPMH [2], native

connected to soil by tubes. Tree-nesting termites may be a

subterranean termites are the most important and the

problem in Puerto Rico and the U.S. Virgin Islands.

most common. These termites include the genus

Reticulitermes, occurring primarily in the continental

The risk for encountering subterranean termites in the

United States, and the genus Heterotermes, occurring in

United States is greater in the southeastern states and in

the Virgin Islands, Puerto Rico, and the deserts of California

southwestern California. In the United States, the risk for

and Arizona. The appearance, habits, and type of damage

termite infestations tends to decrease as the latitude

they cause are similar. The Formosan termite (Coptotermes

increases northward.

formosanus) is the newest species to become established in

the United States. It is a native of the Pacific Islands and

Figure 4.22 portrays the geographic risk of subterranean

spread from Hawaii and Asia to the United States during

termites in the United States. Subterranean termites are

the 1960s. It is now found along the Gulf Coast, in

found in all states except Alaska and are most abundant

California, and in South Carolina, and is expected to

in the south and southeastern United States [18].

spread to other areas as well. Formosan termites cause

greater damage than do native species because of their

According to Potter [19], homeowners can reduce the risk

more vigorous and aggressive behavior and their ability to

for termite attack by adhering to the following suggestions:

rapidly reproduce, build tubes and tunnels, and seek out

new items to infest. They have also shown more resistance

• Eliminate wood contact with the ground. Earth-

to some soil pesticides than native species. Reproductives

to-wood contact provides termites with

(swarmers) are larger than native species, reaching up to

simultaneous access to food, moisture, and shelter

/8-inch in length, and are yellow to brown in color.

in conjunction with direct, hidden entry into the

Swarmers have hairy-looking wings and swarm after dusk,

structure. In addition, the homeowner or

unlike native species, which swarm in the daytime.

occupant should be aware that pressure-treated

Formosan soldiers have more oval-shaped heads than do

wood is not immune to termite attack because

native species. On top of the head is an opening that

termites can enter through the cut ends and build

emits a sticky, whitish substance.

tunnels over the surfaces.

4-10

Disease Vectors and Pests

•

Do not allow moisture to accumulate near the

•

Never store firewood, lumber, or other wood debris

home’s foundation. Proper drainage, repair of

against the foundation or inside the crawl space.

plumbing, and proper grading will help to reduce

Termites are both attracted to and fed by this type

the presence of moisture, which attracts termites.

of storage. Wood stacked in contact with a

dwelling and vines, trellises, and dense plant

•

Reduce humidity in crawl spaces. Most building

material provide a pathway for termites to bypass

codes state that crawl space area should be vented

soil barrier treatment.

at a rate of 1 square foot per 150 square feet of

crawl space area. This rate can be reduced for

•

Use decorative wood chips and mulch sparingly.

crawl spaces equipped with a polyethylene or

Cellulose-containing products attract termites,

equivalent vapor barrier to one square foot per

especially materials that have moisture-holding

300 to 500 square feet of crawl space area. Vent

properties, such as mulch. The homeowner should

placement design includes positioning one vent

never allow these products to contact wood

within 3 feet of each building corner. Trimming

components of the home. The use of crushed

and controlling shrubs so that they do not

stone or pea gravel is recommended as being less

obstruct the vents is imperative. Installling a 4-

attractive to termites and helpful in diminishing

to 6-mil polyethylene sheeting over a minimum of

other pest problems.

75% of the crawl space will reduce the crawl-

space moisture. Covering the entire floor of the

•

Have the structure treated by a professional pest

crawl space with such material can reduce two

control treatment. The final, and most effective,

potential home problems at one time: excess

strategy to prevent infestation is to treat the soil

moisture and radon (Chapter 5). The barrier will

around and beneath the building with termiticide.

reduce the absorption of moisture from the air

The treated ground is then both a repellant and

and the release of moisture into the air in the

toxic to termites.

crawl space from the underlying soil.

Figure 4.22. Subterranean Termite Risk in the United States [18]

Healthy Housing Reference Manual

4-11

Figure 4.23 demonstrates some typical points of attack by

[20], an additional system is to strategically

subterranean termites and some faulty construction practices

place a series of baits around the house. The

that can contribute to subterranean termite infestations.

intention is for termite colonies to encounter one

or more of the baits before approaching the

Lyon [12] notes the following alternative termite control

house. Once termite activity is observed, the bait

measures:

wood is replaced with a poison. The termites

bring the poison back to the colony and the

• Nematodes. Certain species of parasitic round

colony is either eliminated or substantially

worms (nematodes) will infest and kill termites

reduced. This system is relatively new to the

and other soil insects. Varying success has been

market. Its success depends heavily on the

experienced with this method because it is

termites finding the bait before finding and

dependent on several variables, such as soil

damaging the house.

moisture and soil type.

Additional measures include construction techniques that

• Sand as a physical barrier. This would require

discourage termite attacks, as demonstrated in Figure 4.24.

preconstruction planning and would depend on

Termites often invade homes by way of the foundation,

termites being unable to manipulate the sand to

either by crawling up the exterior surface where their

create tunnels. Some research in California and

activity is usually obvious or by traveling inside hollow

Hawaii has indicated early success.

block masonry. One way to deter their activity is to block

their access points on or through the foundation. Metal

• Chemical baits. This method uses wood or

termite shields have been used for decades to deter

laminated texture-flavored cellulose impregnated

termite movement along foundation walls and piers on

with a toxicant and/or insect growth regulator.

up to the wooden structure. Metal termite shields should

The worker termite feeds on the substance and

extend 2 inches from the foundation and 2 inches down.

carries it back to the nest, reducing or eliminating

Improperly installed (i.e., not soldered/sealed properly),

the entire colony. According to HomeReports.com

damaged, or deteriorated termite shields may allow

Figure 4.23. Typical Points of Attack by Termites in the Home [2]

4-12

Disease Vectors and Pests

termites to reach parts of the wooden floor system.

The life cycle of the fire ant begins with the mating of the

Shields should be made of noncorroding metal and have

winged forms (alates) some 300 to 800 feet in the air,

no cracks or gaps along the seams. If a house is being

typically occurring in the late spring or early summer. The

built with metal termite shielding, the shielding should

male dies after the mating; and the newly mated queen

extend at least 2 inches out and 2 inches down at a 45°

finds a suitable moist site, drops her wings, and burrows

angle from the foundation wall. An alternative to using

in the soil, sealing the opening behind her. Ants undergo

termite shields on a hollow-block foundation is to fill the

complete metamorphosis and, therefore, have egg, larval,

block with concrete or put in a few courses of solid or

pupal and adult stages. The new queen will begin laying

concrete-filled brick (which is often done anyway to level

eggs within 24 hours. Once fully developed, she will

foundations). These are referred to as masonry caps. The

produce approximately 1,600 eggs per day over a

same approach can be used with support piers in the

maximum life span of 7 years. Soft, whitish, legless larvae

crawl space. Solid caps (i.e., a continuously poured

are produced from the hatching. These larvae are fed by

concrete cap) are best at stopping termites, but are not

the worker ants. Pupae resemble adults in form, but are

commonly used. Concrete-filled brick caps should deter

soft, nonpigmented, and lack mobility. There are at least

termite movement or force them through small gaps, thus

three distinct castes of ants: workers, queens, and males.

allowing them to be spotted during an inspection [21].

Typically, the males have wings, which they retain until

death. Queens, the largest of the three castes, normally

Fire Ants

have wings, but lose them after mating. The worker,

According to MPMH [2], ants are one of the most

which is also a female, is never winged, except as a rare

numerous species on earth. Ants are in the same order as

abnormality. Within this hierarchy, mature colonies

wasps and bees and, because of their geographic

contain males and females that are capable of flight and

distribution, they are universally recognized (Figure 4.25).

reproduction. These are known as reproductives, and an

Key to Figure 4.23

Cracks in foundation permit hidden points of

11.

Stucco carried down over concrete foundation

entry from soil to sill.

permits hidden entrance between stucco and

foundation if bond fails.

Posts through concrete in contact with

substructural soil. Watch door frames and

12.

Insufficient clearance for inspection also

intermediate supporting posts.

permits easy construction of termite shelter tubes

from soil to wood.

Wood-framing members in contact with

earthfill under concrete slab.

13.

Wood framing of crawl hole forming

wood-soil contact.

Form boards left in place contribute to

termite food supply.

14.

Mud sill and/or posts in contact with soil.

Leaking pipes and dripping faucets sustain soil

15.

Wood siding and skirting form soil contact.

moisture. Excess irrigation has same effect.

There should be a minimum of 3 inches

clearance between skirting and soil.

Shrubbery blocking air flow through vents.

16.

Porch steps in contact with soil. Also watch for

Debris supports termite colony until large

ladders and other wooden materials.

population attacks superstructure.

17.

Downspouts should carry water away from

Heating unit accelerates termite development

the building.

by maintaining warmth of colony on a year-

round basis.

18.

Improper maintenance of soil piled against pier

footing. Also makes careful inspection impossible.

Foundation wall too low permits wood to

contact soil. Adding topsoil often builds exterior

19.

Wall girder entering recess and foundation wall.

grade up to sill level.

Should have a 1-inch free air space on both

sides and end and be protected with a moisture-

10.

Footing too low or soil thrown against it causes

impervious seal.

wood-soil contact. There should be 8 inches

of clean concrete between soil and pier block.

20.

Vents placed between joists tunnel air through

space without providing good substructural

aeration. Vents placed in foundation wall give

better air circulation.

Healthy Housing Reference Manual

4-13

Figure 4.24. Construction Techniques That Discourage Termite Attacks: Thin Metal Termite Shield Should Extend 2 Inches Beyond Foundation and 2 Inches

Down [2]

Alabama. RIFAs are now found in more than 275 million

acres in 11 southern states and Puerto Rico. The second

most important species is the black imported fire ant,

S. richteri, which was introduced into the United States

in the 1920s from Argentina or Uruguay. It is currently

limited in distribution to a small area of northern

Mississippi and Alabama. There are two native species

of fire ants: the tropical or native fire ant, S. geminata,

ranging from South Carolina to Florida and west to

Texas; and the Southern fire ant, S. xyloni, which occurs

from North Carolina south to northern Florida, along the

Gulf Coast, and west to California. The most important

extension of the RIFA range is thought to have occurred

during the 1950s housing boom as a result of the

transportation of sod and nursery plants (Figure 4.26).

Figure 4.25. Fire Ants [22]

RIFAs prefer open and sun-exposed areas. They are found

average colony may produce approximately 4,500 of these

in cultivated fields, cemeteries, parks, and yards, and even

per year. A healthy nest usually produces two nuptial

inside cars, trucks, and recreational vehicles. RIFAs are

flights of reproductives each year and a healthy, mature

attracted to electrical currents and are known to nest in

colony may contain more than 250,000 ants. Though

and around heat pumps, junction boxes, and similar

uncommon among ants, multiple queen colonies (10 to

areas. They are omnivorous; thus they will attack most

100) occur somewhat frequently in fire ants, resulting in

things, living or dead. Their economic effects are felt by

more numerous mounds per acre.

their destruction of the seeds, fruit, shoots, and seedlings

of numerous native plant species. Fire ants are known to

There are many species of fire ants in the United States.

tend pests, such as scale insects, mealy bugs, and aphids,

The most important are four species in the genus

for feeding on their sweet waste excretion (honeydew).

Solenopsis. Of these, the number one fire ant pest is the

RIFAs transport these insects to new feeding sites and

red imported fire ant (RIFA) Solenopsis invicta

protect them from predators. The positive side of RIFA

(Figure 4.25). This ant was imported inadvertently from

infestation is that the fire ant is a predator of ticks and

South America in the 1930s through the port of Mobile,

controls the ground stage of horn flies.

4-14

Disease Vectors and Pests

Figure 4.26. Range Expansion of Red Imported Fire Ants [RIFAs] in the United States, 1918-1998 [23]

The urban dweller with a RIFA infestation may find

Mosquitoes

significant damage to landscape plants, with reductions in

All mosquitoes have four stages of development—egg,

the number of wild birds and mammals. RIFAs can

larva, pupa, and adult—and spend their larval and pupal

discourage outdoor activities and be a threat to young

stages in water. The females of some mosquito species

animals or small confined pets. RIFA nests typically are

deposit eggs on moist surfaces, such as mud or fallen

not found indoors, but around homes, roadways, and

leaves, that may be near water but dry. Later, rain or high

structures, as well as under sidewalks. Shifting of soil after

tides reflood these surfaces and stimulate the eggs to

RIFAs abandon sites has resulted in collapsing structures.

hatch into larvae. The females of other species deposit

Figure 4.27 shows a fire ant mound with fire ants and a

their eggs directly on the surface of still water in such

measure of their relative size.

places as ditches, street catch basins, tire tracks, streams

that are drying up, and fields or excavations that hold

The medical complications of fire ant stings have been

water for some time. This water is often stagnant and

noted in the literature since 1957. People with disabilities,

close to the home in discarded tires, ornamental pools,

reduced feeling in their feet and legs, young children, and

those with mobility issues are at risk for sustaining

numerous stings before escaping or receiving assistance.

Fatalities have resulted from attacks on the elderly and on

infants. Control of the fire ant is primarily focused on the

mound by using attractant bait consisting

of soybean oil, corn grits, or chemical agents. The bait is

picked up by the worker ants and taken deep into the

mound to the queen. These products typically require

weeks to work.

Individual mound treatment is usually most effective in

the spring. The key is to locate and treat all mounds in

the area to be protected. If young mounds are missed, the

Figure 4.27. Fire Ant Mound

area can become reinfested in less than a year.

Source: CAPT Craig Shepherd, U.S. PHS; used with permission.

Healthy Housing Reference Manual

4-15

unused wading and swimming pools, tin cans, bird baths,

When mosquitoes are numerous and interfere with living,

plant saucers, and even gutters and flat roofs. The eggs

recreation, and work, you can use the various measures

soon hatch into larvae. In the hot summer months, larvae

described in the following paragraphs to reduce their

grow rapidly, become pupae, and emerge 1 week later as

annoyance, depending on location and conditions.

flying adult mosquitoes. A few important spring species

have only one generation per year. However, most species

How to Reduce the Mosquito Population

have many generations per year, and their rapid increase

The most efficient method of controlling mosquitoes is

in numbers becomes a problem.

by reducing the availability of water suitable for larval

and pupal growth. Large lakes, ponds, and streams that have

When adult mosquitoes emerge from the aquatic stages,

waves, contain mosquito-eating fish, and lack aquatic

they mate, and the female seeks a blood meal to obtain

vegetation around their edges do not contain mosquitoes;

the protein necessary for the development of her eggs.

mosquitoes thrive in smaller bodies of water in protected

The females of a few species may produce a first batch of

places. Examine your home and neighborhood and take the

eggs without this first blood meal. After a blood meal is

following precautions recommended by the New Jersey

digested and the eggs are laid, the female mosquito again

Agricultural Experiment Station [24]:

seeks a blood meal to produce a second batch of eggs.

Depending on her stamina and the weather, she may

• dispose of unwanted tin cans and tires;

repeat this process many times without mating again. The

male mosquito does not take a blood meal, but may feed

• clean clogged roof gutters and drain flat roofs;

on plant nectar. He lives for only a short time after

mating. Most mosquito species survive the winter, or

• turn over unused wading pools and other

overwinter, in the egg stage, awaiting the spring thaw,

containers that tend to collect rainwater;

when waters warm and the eggs hatch. A few important

species spend the winter as adult, mated females, resting

• change water in birdbaths, fountains, and troughs

in protected, cool locations, such as cellars, sewers, crawl

twice a week;

spaces, and well pits. With warm spring days, these

females seek a blood meal and begin the cycle again.

• clean and chlorinate swimming pools;

Only a few species can overwinter as larvae.

• cover containers tightly with window screen or

Mosquitoborne diseases, such as malaria and yellow fever,

plastic when storing rainwater for garden use

have plagued civilization for thousands of years. Newer threats

during drought periods;

include Lyme disease and West Nile virus. Organized mosquito

control in the United States has greatly reduced the

• flush sump-pump pits weekly; and

incidence of these diseases. However, mosquitoes can still

transmit a few diseases, including eastern equine encephalitis

• stock ornamental pools with fish.

and St. Louis encephalitis. The frequency and extent of

these diseases depend on a complex series of factors.

If mosquito breeding is extensive in areas such as woodland

Mosquito control agencies and health departments cooperate

pools or roadside ditches, the problem may be too great

in being aware of these factors and reducing the chance

for individual residents. In such cases, call the organized

for disease. It is important to recognize that young adult

mosquito control agency in your area. These agencies

female mosquitoes taking their first blood meal do not

have highly trained personnel who can deal with the

transmit diseases. It is instead the older females, who, if they

problem effectively.

have picked up a disease organism in their first blood meals,

can then transmit the disease during the second blood meal.

Several commercially available insecticides can be effective

in controlling larval and adult mosquitoes. These chemicals

The proper method to manage the mosquito problem in

are considered sufficiently safe for use by the public.

a community is through an organized integrated pest

Select a product whose label states that the material is

management system that includes all approaches that safely

effective against mosquito larvae or adults. For safe and

manage the problem. The spraying of toxic agents is but

effective use, read the label and follow the instructions for

one of many approaches.

applying the material. The label lists those insects that the

EPA agrees are effectively controlled by the product.

4-16

Disease Vectors and Pests

For use against adult mosquitoes, some liquid insecticides

Indiana Department of Natural Resources.

can be mixed according to direction and sprayed lightly

Rodent pictures. Lafayette, IN: Indiana

on building foundations, hedges, low shrubbery, ground

Department of Natural Resources; no date.

covers, and grasses. Do not overapply liquid insecticides—

Available from URL: http://www.entm.purdue.edu/

excess spray drips from the sprayed surfaces to the ground,

wildlife/rat_pictures.htm.

where it is ineffective. The purpose of such sprays is to

leave a fine deposit of insecticide on surfaces where mosquitoes

Arrow Services, Inc. Rats: roof rats. Plymouth,

rest. Such sprays are not effective for more than 1 or 2 days.

IN: Arrow Services, Inc.; no date. Available from

URL: http://www.arrowpestcontrol.com/

Some insecticides are available as premixed products or

pages/rod/roofpic.html.

aerosol cans. These devices spray the insecticide as very

small aerosol droplets that remain floating in the air and

Cobb County Extension Service. Fact sheet on

hit the flying mosquitoes. Apply the sprays upwind, so

rodents: rats and mice. Marietta, GA: Cobb

the droplets drift through the area where mosquito

County Extension Service; 2003. Available from

control is desired. Rather than applying too much of

URL: http://www.griffin.peachnet.edu/ga/cobb/

these aerosols initially, it is more practical to apply them

Horticulture/Factsheets/peskycritters/ratsmice.htm.

briefly but periodically, thereby eliminating those

mosquitoes that recently flew into the area.

Kamble ST, Keith DL. Cockroaches and their

control. Lincoln, NE: University of Nebraska

Various commercially available repellents can be

Cooperative Extension; 1995.

purchased as a cream or lotion or in pressurized cans, then

applied to the skin and clothing. Some manufacturers also

University of Nebraska-Lincoln. Cockroach

offer clothing impregnated with repellents; coarse,

picture gallery. Lincoln, NE: University of

repellent-bearing particles to be scattered on the ground;

Nebraska-Lincoln; no date. Available from URL:

and candles whose wicks can be lit to release a repellent

http://pested.unl.edu/roachind.htm.

chemical. The effectiveness of all repellents varies from

location to location, from person to person, and from

Centers for Disease Control and Prevention.

mosquito to mosquito. Repellents can be especially

Reported human plague cases by county: United

effective in recreation areas, where mosquito control may

States, 1970-1997. Atlanta: US Department of

not be conducted. All repellents should be used according

Health and Human Services; no date. Available

to the manufacturers’ instructions. Mosquitoes are

from URL: http://www.cdc.gov/ncidod/

attracted by perspiration, warmth, body odor, carbon

dvbid/plague/plagwest.htm.

dioxide, and light. Mosquito control agencies use some of

these attractants to help determine the relative number of

Leslie M, editor. Netwatch: flys in the Web.

adult mosquitoes in an area. Several devices are sold that

Science 2004;306:1269. Available from URL:

are supposed to attract, trap, and destroy mosquitoes and

http://www.sel.barc.usda.gov/diptera/names/image

other flying insects. However, if these devices are

s/ science1104.pdf.

attractive to mosquitoes, they probably attract more

mosquitoes into the area and may, therefore, increase

10. Oderkirk A. Fly control in poultry barns: poultry

rather than decrease mosquito annoyance.

fact sheet. Truro, Nova Scotia, Canada: Nova Scotia

Department of Agriculture and Marketing; 2001.

References

1. Barnett DB. Vectors and their control. In: Morgan

11. Gold RE, Howell HN Jr, Glenn GJ. Subterranean

MT, editor. Environmental health. 3rd ed.

termites. College Station, TX: Texas Agricultural

Englewood, CO: Wadsworth Publishing Co.;

Extension Service; 1999. Available from URL:

2002. p. 137-50.

http://insects.tamu.edu/extension/bulletins/

b6080.html.

2. Armed Forces Pest Management Board. Military

pest management handbook. Washington, DC:

12. Lyon WF. Termite control: HYG-2092-03.

Armed Forces Pest Management Board; no date.

Columbus, OH: The Ohio State University

Available from URL: http://www.afpmb.org/

Extension; 2003. Available from URL:

MPMH/toc.htm.

http://ohioline.osu.edu/hyg-fact/2000/2092.html.

Healthy Housing Reference Manual

4-17

13. Austin AR. Sample photos of structural

22. Core J. Update: hot on the trail of fire ants. Agric

foundation defects and deficiences. Houston:

Res 2003; 51:20-23. Available from URL:

Diligent Home Inspections; no date.

http://ars.usda. gov/is/AR/archive/

Feb03/ants0203.htm.

14. Fumapest Group. Western subterranean termites.

Revesby, New South Wales, Australia: Fumapest

23. California Department of Food and Agriculture.

Group Pty.; no date. Available from URL:

First reported occurrence of red imported fire ant;

http://www.termite.com/termites/western-

Solenopsis invicta. Sacramento, CA: California

subterranean-termite.html.

Department of Food and Agriculture; no date.

Available from URL: www.cdfa.ca.gov/phpps/pdep/

15. Oi FM, Castner JL, Koehler PG. The Eastern

rifa/html/english/facts/rifaTIME.htm.

subterranean termite. Gainesville, FL: University

of Florida Cooperative Extension Service; 1997.

24. Sutherland DJ, Crans WJ.Mosquitoes in your life.

Available from URL: http://edis.ifas.ufl.edu/

New Jersey Agricultural Experiment Station

BODY_IN031.

Publication SA220-5M-86. New Brunswick, NJ:

New Jersey Agricultural Experiment Station,

16. Ferster B, Deyrup M, Scheffrahn RH. How to tell

Cook College, Rutgers, The State University of

the difference between ant and termite alates. Fort

New Jersey; no date. Available at URL:

Lauderdale, FL: University of Florida; no date.

http://www.rci.rutgers.edu/~insects/moslife.htm.

Available from URL: http://flrec.ifas.ufl.edu/

entomo/ants/Ant%20vs%20Termite.htm.

17. Su N-Y. Life cycle of the Formosan subterranean

termite, Coptotermes formosanus Shiraki.

Gainesville, FL: University of Florida; no date.

Available from URL: http://creatures.ifas.ufl.edu/

urban/termites/fst10.htm.

18. Suiter DR, Jones SC, Forschler BT. Biology of

subterranean termites in the Eastern United

States. Bulletin 1209. Columbus, OH: The Ohio

State University Extension; no date. Available

from URL: http://ohioline.osu.edu/b1209/.

19. Potter MF. Protecting your home against termites.

Lexington, KY: University of Kentucky

Department of Entomology; 2004. Available from

URL: http://www.uky.edu/Agriculture/

Entomology/entfacts/struct/ef605.htm.

20. HomeReports.com. Pest and termite control

companies. Atlanta: HomeReports.com; no date.

Available from URL: http://www.homereports.com/ge/

PestControl.htm.

21. North Carolina Cooperative Extension Service.

Termite prevention: approaches for new

construction. Raleigh, NC: North Carolina

Cooperative Extension Service; no date. Available

from URL: http://www.ces.ncsu.edu/

depts/ent/notes/Urban/termites/pre-con.htm.

4-18

Disease Vectors and Pests

Chapter 5: Indoor Air Pollutants and Toxic Materials

“Walking into a modern building can sometimes be

pollen. These biologic pollutants can be related to some

compared to placing your head inside a plastic bag that is

serious health effects. Some biologic pollutants, such as

filled with toxic fumes.”

measles, chickenpox, and influenza are transmitted

through the air. However, the first two are now

John Bower

preventable with vaccines. Influenza virus transmission,

Founder, Healthy House Institute

although vaccines have been developed, still remains of

concern in crowded indoor conditions and can be

Introduction

affected by ventilation levels in the home.

We all face a variety of risks to our health as we go about

our day-to-day lives. Driving in cars, flying in airplanes,

Common pollutants, such as pollen, originate from

engaging in recreational activities, and being exposed to

plants and can elicit symptoms such as sneezing, watery

environmental pollutants all pose varying degrees of risk.

eyes, coughing, shortness of breath, dizziness, lethargy,

Some risks are simply unavoidable. Some we choose to

fever, and digestive problems. Allergic reactions are the

accept because to do otherwise would restrict our ability

result of repeated exposure and immunologic

to lead our lives the way we want. Some are risks we

sensitization to particular biologic allergens.

might decide to avoid if we had the opportunity to make

informed choices. Indoor air pollution and exposure to

Although pollen allergies can be bothersome, asthmatic

hazardous substances in the home are risks we can do

responses to pollutants can be life threatening. Asthma is

something about.

a chronic disease of the airways that causes recurrent and

distressing episodes of wheezing, breathlessness, chest

In the last several years, a growing body of scientific

tightness, and coughing [2]. Asthma can be broken

evidence has indicated that the air within homes and

down into two groups based on the causes of an attack:

other buildings can be more seriously polluted than the

extrinsic (allergic) and intrinsic (nonallergic). Most

outdoor air in even the largest and most industrialized

people with asthma do not fall neatly into either type,

cities. Other research indicates that people spend

but somewhere in between, displaying characteristics of

approximately 90% of their time indoors. Thus, for

both classifications. Extrinsic asthma has a known cause,

many people, the risks to health from exposure to indoor

such as allergies to dust mites, various pollens, grass or

air pollution may be greater than risks from outdoor

weeds, or pet danders. Individuals with extrinsic asthma

pollution.

produce an excess amount of antibodies when exposed to

triggers. Intrinsic asthma has a known cause, but the

In addition, people exposed to indoor air pollutants for

connection between the cause and the symptoms is not

the longest periods are often those most susceptible to

clearly understood. There is no antibody hypersensitivity

their effects. Such groups include the young, the elderly,

in intrinsic asthma. Intrinsic asthma usually starts in

and the chronically ill, especially those suffering from

adulthood without a strong family history of asthma.

respiratory or cardiovascular disease [1].

Some of the known triggers of intrinsic asthma are

infections, such as cold and flu viruses, exercise and cold

Indoor Air Pollution

air, industrial and occupational pollutants, food additives

Numerous forms of indoor air pollution are possible in

and preservatives, drugs such as aspirin, and emotional

the modern home. Air pollutant levels in the home

stress. Asthma is more common in children than in

increase if not enough outdoor air is brought in to dilute

adults, with nearly 1 of every 13 school-age children

emissions from indoor sources and to carry indoor air

having asthma [3]. Low-income African-Americans and

pollutants out of the home. In addition, high temperature and

certain Hispanic populations suffer disproportionately,

humidity levels can increase the concentration of some

with urban inner cities having particularly severe

pollutants. Indoor pollutants can be placed into two

problems. The impact on neighborhoods, school

groups, biologic and chemical.

systems, and health care facilities from asthma is severe

because one-third of all pediatric emergency room visits

Biologic Pollutants

are due to asthma, and it is the fourth most prominent

Biologic pollutants include bacteria, molds, viruses,

cause of physician office visits. Additionally, it is the

animal dander, cat saliva, dust mites, cockroaches, and

leading cause of school absenteeism—14 million school

Healthy Housing Reference Manual

5-1

days lost each year—from chronic illness [4]. The U.S.

microhabitat for the accumulation of food and moisture

population, on the average, spends as much as 90% of its

for the mite, and also provide protection from removal by

time indoors. Consquently, allergens and irritants from

vacuuming. The house dust mite’s favorite food is human

the indoor environment may play a significant role in

dander (skin flakes), which are shed at a rate of

triggering asthma episodes. A number of indoor

approximately 0.20 ounces per week.

environmental asthma triggers are biologic pollutants.

These can include rodents (discussed in Chapter 4),

A good microscope and a trained observer are imperative

cockroaches, mites, and mold.

in detecting mites. House dust mites also can be detected

using diagnostic tests that measure the presence and

Cockroaches

infestation level of mites by combining dust samples

The droppings, body parts, and saliva of cockroaches can

collected from various places inside the home with

be asthma triggers. Cockroaches are commonly found in

indicator reagents [7]. Assuming the presence of mites,

crowded cities and in the southern United States.

the precautions listed below should be taken if people

Allergens contained in the feces and saliva of cockroaches

with asthma are present in the home:

can cause allergic reactions or trigger asthma symptoms. A

national study by Crain et al. [5] of 994 inner-city allergic

•

Use synthetic rather than feather and down pillows.

children from seven U.S. cities revealed that cockroaches

were reported in 58% of the homes. The Community

•

Use an approved allergen barrier cover to enclose

Environmental Health Resource Center reports that

the top and sides of mattresses and pillows and

cockroach debris, such as body parts and old shells,

the base of the bed.

trigger asthma attacks in individuals who are sensitized to

cockroach allergen [6]. Special attention to cleaning must

•

Use a damp cloth to dust the plastic mattress

be a priority after eliminating the presence of cockroaches

cover daily.

to get rid of the presence of any allergens left that can be

asthma triggers.

•

Change bedding and vacuum the bed base and

mattress weekly.

House Dust Mites

Another group of arthropods linked to asthma is house

•

Use nylon or cotton cellulose blankets rather than

dust mites. In 1921, a link was suggested between

wool blankets.

asthmatic symptoms and house dust, but it was not until

1964 that investigators suggested that a mite could be

•

Use hot (120°F-130°F [49°C-54°C]) water to

responsible. Further investigation linked a number of mite

wash all bedding, as well as room curtains.

species to the allergen response and revealed that humid

homes have more mites and, subsequently, more allergens.

•

Eliminate or reduce fabric wall hangings, curtains,

In addition, researchers established that fecal pellets

and drapes.

deposited by the mites accumulated in home fabrics and

could become airborne via domestic activities such as

•

Use wood, tile, linoleum, or vinyl floor covering

vacuuming and dusting, resulting in inhalation by the

rather than carpet. If carpet is present, vacuum

inhabitants of the home. House dust mites are distributed

regularly with a high-efficiency particulate air

worldwide, with a minimum of 13 species identified from

(HEPA) vacuum or a household vacuum with a

house dust. The two most common in the United States

microfiltration bag.

are the North American house dust mite

(Dermatophagoides farinae) and the European house dust

•

Purchase stuffed toys that are machine washable.

mite (D. pteronyssinus). According to Lyon [7], house dust

mites thrive in homes that provide a source of food and

•

Use fitted sheets to help reduce the accumulation

shelter and adequate humidity. Mites prefer relative

of human skin on the mattress surface.

humidity levels of 70% to 80% and temperatures of 75°F

to 80°F (24°C to 27°C). Most mites are found in

HEPA vacuums are now widely available and have also

bedrooms in bedding, where they spend up to a third of

been shown to be effective [8]. A conventional vacuum

their lives. A typical used mattress may have from

tends to be inefficient as a control measure and results in

100,000 to 10 million mites in it. In addition, carpeted

a significant increase in airborne dust concentrations, but

floors, especially long, loose pile carpet, provide a

can be used with multilayer microfiltration collection

5-2

Indoor Air Pollutants and Toxic Materials

bags. Another approach to mite control is reducing

matter and, provided with sufficient moisture, can live off

indoor humidity to below 50% and installing central

of many materials found in homes, such as wood,

air conditioning.

cellulose in the paper backing on drywall, insulation,

wallpaper, glues used to bond carpet to its backing, and

Two products are available to treat house dust mites and

everyday dust and dirt.

their allergens. These products contain the active

ingredients benzyl benzoate and tannic acid.

Certain molds can cause a variety of adverse human

health effects, including allergic reactions and immune

Pets

responses (e.g., asthma), infectious disease (e.g.,

According to the U.S. Environmental Protection Agency

histoplasmosis), and toxic effects (e.g., aflatoxin-induced

(EPA) [9], pets can be significant asthma triggers because

liver cancer from exposure to this mold-produced toxin in

of dead skin flakes, urine, feces, saliva, and hair. Proteins

food) [14]. A recent Institute of Medicine (IOM) review

in the dander, urine, or saliva of warm-blooded animals

of the scientific literature found sufficient evidence for an

can sensitize individuals and lead to allergic reactions or

association between exposure to mold or other agents in

trigger asthmatic episodes. Warm-blooded animals

damp indoor environments and the following conditions:

include dogs, cats, birds, and rodents (hamsters, guinea

upper respiratory tract symptoms, cough, wheeze,

pigs, gerbils, rats, and mice). Numerous strategies, such as

hypersensitivity pneumonitis in susceptible persons, and

the following, can diminish or eliminate animal allergens

asthma symptoms in sensitized persons [15]. A previous

in the home:

scientific review was more specific in concluding that

sufficient evidence exists to support associations between

• Eliminate animals from the home.

fungal allergen exposure and asthma exacerbation and

upper respiratory disease [13]. Finally, mold toxins can

• Thoroughly clean the home (including floors and

cause direct lung damage leading to pulmonary diseases

walls) after animal removal.

other than asthma [13].

• If pets must remain in the home, reduce pet

The topic of residential mold has received increasing

exposure in sleeping areas. Keep pets away from

public and media attention over the past decade. Many

upholstered furniture, carpeted areas, and stuffed

news stories have focused on problems associated with

toys, and keep the pets outdoors as much

“toxic mold” or “black mold,” which is often a reference

as possible.

to the toxin-producing mold, Stachybotrys chartarum. This

might give the impression that mold problems in homes

However, there is some evidence that pets introduced

are more frequent now than in past years; however, no

early into the home may prevent asthma. Several studies

good evidence supports this. Reasons for the increasing

have shown that exposure to dogs and cats in the first

attention to this issue include high-visibility lawsuits

year of life decreases a child’s chances of developing

brought by property owners against builders and

allergies [10] and that exposure to cats significantly

developers, scientific controversies regarding the degree to

decreases sensitivity to cats in adulthood [11]. Many

which specific illness outbreaks are mold-induced, and an

other studies have shown a decrease in allergies and

increase in the cost of homeowner insurance policies due

asthma among children who grew up on a farm and were

to the increasing number of mold-related claims. Modern

around many animals [12].

construction might be more vulnerable to mold problems

because tighter construction makes it more difficult for

Mold

internally generated water vapor to escape, as well as the

People are routinely exposed to more than 200 species of

widespread use of paper-backed drywall in construction

fungi indoors and outdoors [13]. These include moldlike

(paper is an excellent medium for mold growth when

fungi, as well as other fungi such as yeasts and

wet), and the widespread use of carpeting.

mushrooms. The terms “mold” and “mildew” are

nontechnical names commonly used to refer to any fungus

Allergic Health Effects. Many molds produce numerous

that is growing in the indoor environment. Mold colonies

protein or glycoprotein allergens capable of causing

may appear cottony, velvety, granular, or leathery, and

allergic reactions in people. These allergens have been

may be white, gray, black, brown, yellow, greenish, or

measured in spores as well as in other fungal fragments.

other colors. Many reproduce via the production and

An estimated 6%-10% of the general population and

dispersion of spores. They usually feed on dead organic

15%-50% of those who are genetically susceptible are

Healthy Housing Reference Manual

5-3

sensitized to mold allergens [13]. Fifty percent of the

also be caused by the production of excess moisture

937 children tested in a large multicity asthma study

within homes from humidifiers, unvented clothes dryers,

sponsored by the National Institutes of Health showed

overcrowding, etc. Finished basements are particularly

sensitivity to mold, indicating the importance of mold as

susceptible to mold problems caused by the combination

an asthma trigger among these children [16]. Molds are

of poorly controlled moisture and mold-supporting

thought to play a role in asthma in several ways. Molds

materials (e.g., carpet, paper-backed sheetrock) [15].

produce many potentially allergenic compounds, and

There is also some evidence that mold spores from damp

molds may play a role in asthma via release of irritants

or wet crawl spaces can be transported through air currents

that increase potential for sensitization or release of toxins

into the upper living quarters. Older, substandard

(mycotoxins) that affect immune response [13].

housing low income families can be particularly prone to

mold problems because of inadequate maintenance (e.g.,

Toxics and Irritants. Many molds also produce

inoperable gutters, basement and roof leaks), overcrowding,

mycotoxins that can be a health hazard on ingestion,

inadequate insulation, lack of air conditioning, and poor

dermal contact, or inhalation [14]. Although common

heating. Low interior temperatures (e.g., when one or two

outdoor molds present in ambient air, such as

rooms are left unheated) result in an increase in the

Cladosporium cladosporioides and Alternaria alternata, do

relative humidity, increasing the potential for water to

not usually produce toxins, many other different mold

condense on cold surfaces.

species do [17]. Genera-producing fungi associated with

wet buildings, such as Aspergillus versicolor, Fusarium

Mold Assessment Methods. Mold growth or the

verticillioides, Penicillium aiurantiorisen, and S. chartarum,

potential for mold growth can be detected by visual

can produce potent toxins [17]. A single mold species

inspection for active or past microbial growth, detection

may produce several different toxins, and a given

of musty odors, and inspection for water staining or

mycotoxin may be produced by more than one species of

damage. If it is not possible or practical to inspect a

fungi. Furthermore, toxin-producing fungi do not

residence, this information can be obtained using

necessarily produce mycotoxins under all growth

occupant questionnaires. Visual observation of mold

conditions, with production being dependent on the

growth, however, is limited by the fact that fungal

substrate it is metabolizing, temperature, water content,

elements such as spores are microscopic, and that their

and humidity [17]. Because species of toxin-producing

presence is often not apparent until growth is extensive

molds generally have a higher water requirement than do

and the fact that growth can occur in hidden spaces (e.g.,

common household molds, they tend to thrive only under

wall cavities, air ducts).

conditions of chronic and severe water damage [18]. For

example, Stachybotrys typically only grows under continuously

Portable, hand-held moisture meters, for the direct

wet conditions [19]. It has been suggested that very

measurement of moisture levels in materials, may also be

young children may be especially vulnerable to certain

useful in qualitative home assessments to aid in

mycotoxins [19,20]. For example, associations have been

pinpointing areas of potential biologic growth that may

reported for pulmonary hemorrhage (bleeding lung)

not otherwise be obvious during a visual inspection [14].

deaths in infants and the presence of S. chartarum [21-24].

For routine assessments in which the goal is to identify

Causes of Mold. Mold growth can be caused by any

possible mold contamination problems before

condition resulting in excess moisture. Common moisture

remediation, it is usually unnecessary to collect and

sources include rain leaks (e.g., on roofs and wall joints);

analyze air or settled dust samples for mold analysis

surface and groundwater leaks (e.g., poorly designed or

because decisions about appropriate intervention

clogged rain gutters and footing drains, basement leaks);

strategies can typically be made on the basis of a visual

plumbing leaks; and stagnant water in appliances (e.g.,

inspection [25]. Also, sampling and analysis costs can be

dehumidifiers, dishwashers, refrigerator drip pans, and

relatively high and the interpretation of results is not

condensing coils and drip pans in HVAC systems).

straightforward. Air and dust monitoring may, however,

Moisture problems can also be due to water vapor

be necessary in certain situations, including 1) if an

migration and condensation problems, including uneven

individual has been diagnosed with a disease associated

indoor temperatures, poor air circulation, soil air entry

with fungal exposure through inhalation, 2) if it is

into basements, contact of humid unconditioned air with

suspected that the ventilation systems are contaminated,

cooled interior surfaces, and poor insulation on indoor

or 3) if the presence of mold is suspected but cannot be

chilled surfaces (e.g., chilled water lines). Problems can

identified by a visual inspection or bulk sampling [26].

5-4

Indoor Air Pollutants and Toxic Materials

Generally, indoor environments contain large reservoirs of

exposure, some organizations support a precautionary

mold spores in settled dust and contaminated building

approach to limiting mold exposure [19]. For example,

materials, of which only a relatively small amount is

the American Academy of Pediatrics recommends that

airborne at a given time.

infants under 1 year of age are not exposed at all to

chronically moldy, water-damaged environments [18].

Common methods for sampling for mold growth include

bulk sampling techniques, air sampling, and collection of

Mold Mitigation. Common intervention methods for

settled dust samples. In bulk sampling, portions of

addressing mold problems include the following:

materials with visual or suspected mold growth (e.g., sections

of wallboard, pieces of duct lining, carpet segments, or

•

maintaining heating, ventilating, and air

return air filters) are collected and directly examined to

conditioning (HVAC) systems;

determine if mold is growing and to identify the mold

species or groups that are present. Surface sampling in

•

changing HVAC filters frequently, as

mold contamination investigations may also be used

recommended by manufacturer;

when a less destructive technique than bulk sampling is

desired. For example, nondestructive samples of mold may

•

keeping gutters and downspouts in working order

be collected using a simple swab or adhesive tape [14].

and ensuring that they drain water away from the

foundation;

Air can also be sampled for mold using pumps that pull

air across a filter medium, which traps airborne mold

•

routinely checking, cleaning, and drying drip pans

spores and fragments. It is generally recommended that

in air conditioners, refrigerators, and

outdoor air samples are collected concurrent with indoor

dehumidifiers;

samples for comparison purposes for measurement of

baseline ambient air conditions. Indoor contamination

•

increasing ventilation (e.g., using exhaust fans or

can be indicated by indoor mold distributions (both

open windows to remove humidity when cooking,

species and concentrations) that differ significantly from

showering, or using the dishwasher);

the distributions in outdoor samples [14]. Captured mold

spores can be examined under a microscope to identify

•

venting clothes dryers to the outside; and

the mold species/groups and determine concentrations or

they can be cultured on growth media and the resulting

•

maintaining an ideal relative humidity level in the

colonies counted and identified. Both techniques require

home of 40% to 60%.

considerable expertise.

•

locating and removing sources of moisture

Dust sampling involves the collection of settled dust

(controlling dampness and humidity and repairing

samples (e.g., floor dust) using a vacuum method in

water leakage problems);

which the dust is collected onto a porous filter medium

or into a container. The dust is then processed in the

•

cleaning or removing mold-contaminated

laboratory and the mold identified by culturing viable spores.

materials;

Mold Standards. No standard numeric guidelines exist

•

removing materials with severe mold growth; and

for assessing whether mold contamination exists in an

area. In the United States, no EPA regulations or

•

using high-efficiency air filters.

standards exist for airborne mold contaminants [26].

Various governmental and private organizations have,

Moisture Control. Because one of the most important

however, proposed guidance on the interpretation of

factors affecting mold growth in homes is moisture level,

fungal measures of environmental media in indoor

controlling this factor is crucial in mold abatement

environments (quantitative limits for fungal

strategies. Many simple measures can significantly control

concentrations).

moisture, for example maintaining indoor relative

humidity at no greater than 40%-60% through the use

Given evidence that young children may be especially

of dehumidifiers, fixing water leakage problems,

vulnerable to certain mycotoxins [18] and in view of the

increasing ventilation in kitchens and bathrooms by using

potential severity or diseases associated with mycotoxin

exhaust fans, venting clothes dryers to the outside,

Healthy Housing Reference Manual

5-5

reducing the number of indoor plants, using air

(available from URL: http://www.nyc.gov/html/

conditioning at times of high outdoor humidity, heating

doh/html/epi/moldrpt1.shtml).

all rooms in the winter and adding heating to outside wall

closets, sloping surrounding soil away from building

•

American Conference of Governmental Industrial

foundations, fixing gutters and downspouts, and using a

Hygienists (ACGIH) 1999 document,

sump pump in basements prone to flooding [27]. Vapor

Biosaerosols: Assessment and Control (can be

barriers, sump pumps, and aboveground vents can also be

ordered at URL http://www.acgih.org/home.htm).

installed in crawlspaces to prevent moisture problems [28].

•

American Industrial Hygiene Association (AIHA)

Removal and Cleaning of Mold-contaminated Materials.

2004 document, Assessment, Remediation, and

Nonporous (e.g., metals, glass, and hard plastics) and

Post-Remediation Verification of Mold in

semiporous (e.g., wood and concrete) materials

Buildings (can be ordered at URL www.aiha.org)

contaminated with mold and that are still structurally

sound can often be cleaned with bleach-and-water

•

Environmental Protection Agency guidance, Mold

solutions. However, in some cases, the material may not

Remediation in Schools and Commercial Buildings

be easily cleaned or may be so severely contaminated that

(includes many general principles also applicable

it may have to be removed. It is recommended that

to residential mold mitigation efforts; available at

porous materials (e.g., ceiling tiles, wallboards, and

URL: http://www.epa.gov/iaq/molds/

fabrics) that cannot be cleaned be removed and discarded

mold_remediation.html)

[29]. In severe cases, clean-up and repair of mold-

contaminated buildings may be conducted using methods

•

Environmental Protection Agency guidance, A

similar to those used for abatement of other hazardous

Brief Guide to Mold, Moisture, and Your Home

substances such as asbestos [30]. For example, in

(for homeowners and renters on how to clean up

situations of extensive colonization (large surface areas

residential mold problems and how to prevent

greater than 100 square feet or where the material is

mold growth; available at URL: http://www.epa.gov/

severely degraded), extreme precautions may be required,

iaq/molds/images/moldguide.pdf)

including full containment (complete isolation of work

area) with critical barriers (airlock and decontamination

•

Canada Mortgage and Housing Corporation,

room) and negative pressurization, personnel trained to

Clean-up Procedures for Mold in Houses,

handle hazardous wastes, and the use of full-face

(provides qualitative guidance for mold

respirators with HEPA filters, eye protection, and

mitigation; can be ordered at URL:

disposable full-body covering [26].

https://www.cmhc-schl.gc.ca:50104/b2c/b2c/

init.do?language=en).

Worker Protection When Conducting Mold Assessment

and Mitigation Projects. Activities such as cleaning or

Figure 5.1 shows mold growth in the home.

removal of mold-contaminated materials in homes, as well

as investigations of mold contamination extent, have the

Chemical Pollutants

potential to disturb areas of mold growth and release

Carbon Monoxide

fungal spores and fragments into the air. Recommended

Carbon monoxide (CO) is a significant combustion

measures to protect workers during mold remediation

pollutant in the United States. CO is a leading cause of

efforts depend on the severity and nature of the mold

poisoning deaths [32]. According to the National Fire

contamination being addressed, but include the use of

Protection Association (NFPA), CO-related nonfire

well fitted particulate masks or respirators that retain

deaths are often attributed to heating and cooking

particles as small as 1 micrometer or less, disposable

equipment. The leading specific types of equipment

gloves and coveralls, and protective eyewear [31].

blamed for CO-related deaths include gas-fueled space

heaters, gas-fueled furnaces, charcoal grills, gas-fueled

Following are examples of guidance documents for

ranges, portable kerosene heaters, and wood stoves.

remediation of mold contamination:

As with fire deaths, the risk for unintentional CO death is

• New York City Department of Health and Mental

highest for the very young (ages 4 years and younger) and

Hygiene. Guidelines on Assessment and

the very old (ages 75 years and older). CO is an odorless,

Remediation of Fungi in Indoor Environments

colorless gas that can cause sudden illness and death. It is

5-6

Indoor Air Pollutants and Toxic Materials

•

Assure that all gas heaters

possess safety devices that

shut off an improperly

vented gas heater. Heaters

made after 1982 use a

pilot light safety system

known as an oxygen

depletion sensor. When

inadequate fresh air exists,

this system shuts off the

heater before large

amounts of CO can

be produced.

Figure 5.1. Mold Growth in the Home

•

Use appliances that have

Figure 5.2. Home Carbon

Monoxide Monitor

electronic ignitions instead

a result of the incomplete combustion of carbon.

Source: U.S. Navy

of pilot lights. These

Headache, dizziness, weakness, nausea, vomiting, chest

appliances are typically more energy efficient and

pain, and confusion are the most frequent symptoms of

eliminate the continuous low-level pollutants

CO poisoning. According to the American Lung

from pilot lights.

Association (ALA) [33], breathing low levels of CO can

cause fatigue and increase chest pain in people with

• Use the proper fuel in kerosene appliances.

chronic heart disease. Higher levels of CO can cause

flulike symptoms in healthy people. In addition,

• Install and use an exhaust fan vented to the

extremely high levels of CO cause loss of consciousness

outdoors over gas stoves.

and death. In the home, any fuel-burning appliance that

is not adequately vented and maintained can be a

•

Have a trained professional annually inspect,

potential source of CO. The following steps should be

clean, and tune up central heating systems

followed to reduce CO (as well as sulfur dioxide and

(furnaces, flues, and chimneys) and repair them

oxides of nitrogen) levels:

as needed.

•

Never use gas-powered equipment, charcoal grills,

• Do not idle a car inside a garage.

hibachis, lanterns, or portable camping stoves in

enclosed areas or indoors.

The U.S. Consumer Product Safety Commission (CPSC)

recommends installing at least one CO alarm per household

•

Install a CO monitor (Figure 5.2) in appropriate

near the sleeping area. For an extra measure of safety,

areas of the home. These monitors are designed to

another alarm should be placed near the home’s heating

provide a warning before potentially life-

source. ALA recommends weighing the benefits of using

threatening levels of CO are reached.

models powered by electrical outlets versus models powered by

batteries that run out of power and need replacing.

•

Choose vented appliances when possible and keep

Battery-powered CO detectors provide continuous protection

gas appliances properly adjusted to decrease the

and do not require recalibration in the event of a power

combustion to CO. (Note: Vented appliances are

outage. Electric-powered systems do not provide protection

always preferable for several reasons: oxygen levels,

during a loss of power and can take up to 2 days to

carbon dioxide buildup, and humidity management).

recalibrate. A device that can be easily self-tested and reset

to ensure proper functioning should be chosen. The product

• Only buy certified and tested combustion

should meet Underwriters Laboratories Standard UL 2034.

appliances that meet current safety standards, as

certified by Underwriter’s Laboratories (UL),

Ozone

American Gas Association (AGA) Laboratories, or

Inhaling ozone can damage the lungs. Inhaling small amounts

equivalent.

of ozone can result in chest pain, coughing, shortness of

breath, and throat irritation. Ozone can also exacerbate

Healthy Housing Reference Manual

5-7

chronic respiratory diseases such as asthma. Susceptibility

in nonsmokers due to ETS. Additionally, passive smoking

to the effects of ozone varies from person to person, but

can lead to coughing, excess phlegm, and chest

even healthy people can experience respiratory difficulties

discomfort. NCI also notes that spontaneous abortion

from exposure.

(miscarriage), cervical cancer, sudden infant death

syndrome, low birth weight, nasal sinus cancer, decreased

According to the North Carolina Department of Health

lung function, exacerbation of cystic fibrosis, and negative

and Human Services [34], the major source of indoor

cognitive and behavioral effects in children have been

ozone is outdoor ozone. Indoor levels can vary from 10% of

linked to ETS [36].

the outdoor air to levels as high as 80% of the outdoor air.

The Food and Drug Administration has set a limit of

The EPA [37] states that, because of their relative body

0.05 ppm of ozone in indoor air. In recent years, there

size and respiratory rates, children are affected by ETS

have been numerous advertisements for ion generators that

more than adults are. It is estimated that an additional

destroy harmful indoor air pollutants. These devices create

7,500 to 15,000 hospitalizations resulting from increased

ozone or elemental oxygen that reacts with pollutants.

respiratory infections occur in children younger than

EPA has reviewed the evidence on ozone generators and

18 months of age due to ETS exposure. Figure 5.3 shows

states: “available scientific evidence shows that at

the ETS exposure levels in homes with children under age

concentrations that do not exceed public health standards,

7 years. The following actions are recommended in the

ozone has little potential to remove indoor air contaminants,”

home to protect children from ETS:

and “there is evidence to show that at concentrations that

do not exceed public health standards, ozone is not

• if individuals insist on smoking, increase

effective at removing many odor causing chemicals” [35].

ventilation in the smoking area by opening

windows or using exhaust fans; and

Ozone is also created by the exposure of polluted air to

sunlight or ultraviolet light emitters. This ozone produced

• refrain from smoking in the presence of children

outside of the home can infiltrate the house and react

and do not allow babysitters or others who work

with indoor surfaces, creating additional pollutants.

in the home to smoke in the home or near children.

Environmental Tobacco Smoke or Secondhand Smoke

Volatile Organic Compounds

Like CO, environmental tobacco smoke (ETS; also

In the modern home, many organic chemicals are used as

known as secondhand smoke), is a product of

ingredients in household products. Organic chemicals

combustion. The National Cancer Institute (NCI) [36],

that vaporize and become gases at normal room

states that ETS is the combination of two forms of smoke

temperature are collectively known as VOCs.

from burning tobacco products:

Examples of common items that can release VOCs

• Sidestream smoke, or smoke that is emitted

include paints, varnishes, and wax, as well as in many

between the puffs of a burning cigarette, pipe, or

cleaning, disinfecting, cosmetic, degreasing, and hobby

cigar; and

products. Levels of approximately a dozen common

VOCs can be two to five times higher inside the home, as

• Mainstream smoke, or the smoke that is exhaled

opposed to outside, whether in highly industrialized areas

by the smoker.

The physiologic effects of ETS are numerous. ETS can

trigger asthma; irritate the eyes, nose, and throat; and

cause ear infections in children, respiratory illnesses, and

lung cancer. ETS is believed to cause asthma by irritating

chronically inflamed bronchial passages. According to the

EPA [37], ETS is a Group A carcinogen; thus, it is a

known cause of cancer in humans. Laboratory analysis

has revealed that ETS contains in excess of

4,000 substances, more than 60 of which cause cancer

in humans or animals. The EPA also estimates that

Figure 5.3. Environmental Tobacco Smoke and Children’s Exposure [37]

approximately 3,000 lung cancer deaths occur each year

5-8

Indoor Air Pollutants and Toxic Materials

or rural areas. VOCs that frequently pollute indoor air

decline with time. In 1982, CPSC voted to ban UF foam

include toluene, styrene, xylenes, and trichloroethylene.

insulation. The courts overturned the ban; however, the

Some of these chemicals may be emitted from aerosol

publicity has decreased the use of this product.

products, dry-cleaned clothing, paints, varnishes, glues,

art supplies, cleaners, spot removers, floor waxes, polishes,

More recently, the most significant source of

and air fresheners. The health effects of these chemicals

formaldehyde in homes has been pressed wood products

are varied. Trichlorethylene has been linked to childhood

made using adhesives that contain UF resins [41]. The

leukemia. Exposure to toluene can put pregnant women

most significant of these is medium-density fiberboard,

at risk for having babies with neurologic problems,

which contains a higher resin-to-wood ratio than any

retarded growth, and developmental problems. Xylenes

other UF pressed wood product. This product is generally

have been linked to birth defects. Styrene is a suspected

recognized as being the highest formaldehyde-emitting

endocrine disruptor, a chemical that can block or mimic

pressed wood product. Additional pressed wood products

hormones in humans or animals. EPA data reveal that

are produced using phenol-formaldehyde resin. The latter

methylene chloride, a common component of some paint

type of resin generally emits formaldehyde at a

strippers, adhesive removers, and specialized aerosol spray

considerably slower rate than those containing UF resin.

paints, causes cancer in animals [38]. Methylene chloride

The emission rate for both resins will change over time

is also converted to CO in the body and can cause

and will be influenced by high indoor temperatures and

symptoms associated with CO exposure. Benzene, a

humidity. Since 1985, U.S. Department of Housing and

known human carcinogen, is contained in tobacco smoke,

Urban Development (HUD) regulations (24 CFR 3280.308,

stored fuels, and paint supplies. Perchloroethylene, a

3280.309, and 3280.406) have permitted only the use of

product uncommonly found in homes, but common to

plywood and particleboard that conform to specified

dry cleaners, can be a pollution source by off-gassing from

formaldehyde emission limits in the construction of

newly cleaned clothing. Environmental Media Services

prefabricated and manufactured homes [42]. This limit was

[39] also notes that xylene, ketones, and aldehydes are

to ensure that indoor formaldehyde levels are below 0.4 ppm.

used in aerosol products and air fresheners.

CPSC [40] notes that formaldehyde is a colorless, strong-

To lower levels of VOCs in the home, follow these steps:

smelling gas. At an air level above 0.1 ppm, it can cause

watery eyes; burning sensations in the eyes, nose, and

• use all household products according to directions;

throat; nausea; coughing; chest tightness; wheezing; skin

rashes; and allergic reactions. Laboratory animal studies

• provide good ventilation when using these products;

have revealed that formaldehyde can cause cancer in

animals and may cause cancer in humans. Formaldehyde

• properly dispose of partially full containers of old

is usually present at levels less than 0.03 ppm indoors and

or unneeded chemicals;

outdoors, with rural areas generally experiencing lower

concentrations than urban areas. Indoor areas that

• purchase limited quantities of products; and

contain products that release formaldehyde can have levels

greater than 0.03 ppm. CPSC also recommends the

• minimize exposure to emissions from products

following actions to avoid high levels of exposure to

containing methylene chloride, benzene, and

formaldehyde:

perchlorethylene.

• Purchase pressed wood products that are labeled

A prominent VOC found in household products and

or stamped to be in conformance with American

construction products is formaldehyde. According to

National Standards Institute criteria ANSI

CPSC [40], these products include the glue or adhesive

A208.1-1993. Use particleboard flooring marked

used in pressed wood products; preservatives in paints,

with ANSI grades PBU, D2, or D3. Medium-

coating, and cosmetics; coatings used for permanent-press

density fiberboard should be in conformance with

quality in fabrics and draperies; and the finish on paper

ANSI A208.2-1994 and hardwood plywood with

products and certain insulation materials. Formaldehyde

ANSI/HPVA HP-1-1994 (Figure 5.4).

is contained in urea-formaldehyde (UF) foam insulation

installed in the wall cavities of homes as an energy

• Purchase furniture or cabinets that contain a high

conservation measure. Levels of formaldehyde increase

percentage of panel surface and edges that are

soon after installation of this product, but these levels

laminated or coated. Unlaminated or uncoated

Healthy Housing Reference Manual

5-9

levels in the United States. Maps of the individual states

and areas that have proven high for radon are available at

http://www.epa.gov/iaq/radon/ zonemap.html. A free

video is available from the U.S. EPA: call 1-800-438-

4318 and ask for EPA 402-V-02-003 (TRT 13.10).

Radon, according to the California Geological Survey

Figure 5.4. Wood Products Label [42]

[45], is one of the intermediate radioactive elements

formed during the radioactive decay of uranium-238,

(raw) panels of pressed wood panel products will

uranium-235, or thorium-232. Radon-222 is the radon

generally emit more formaldehyde than those that

isotope of most concern to public health because of its

are laminated or coated.

longer half-life (3.8 days). The mobility of radon gas is

much greater than are uranium and radium, which are

• Use alternative products, such as wood panel

solids at room temperature. Thus, radon can leave rocks

products not made with UF glues, lumber, or metal.

and soil, move through fractures and pore spaces, and

ultimately enter a building to collect in high concentrations.

• Avoid the use of foamed-in-place insulation

When in water, radon moves less than 1 inch before it

containing formaldehyde, especially UF foam

decays, compared to 6 feet or more in dry rocks or soil.

insulation.

USGS [44] notes that radon near the surface of soil

typically escapes into the atmosphere. However,

• Wash durable-press fabrics before use.

where a house is present, soil air often flows toward the

house foundation because of

CPSC also recommends the following actions to reduce

existing levels of indoor formaldehyde:

• Ventilate the home well by opening doors and

windows and installing an exhaust fan(s).

• Seal the surfaces of formaldehyde-containing

products that are not laminated or coated with

paint, varnish, or a layer of vinyl or polyurethane-

like materials.

• Remove products that release formaldehyde in the

indoor air from the home.

Radon

According to the EPA [43], radon is a colorless, odorless

gas that occurs naturally in soil and rock and is a decay

product of uranium. The U.S. Geological Survey (USGS)

Figure 5.5. EPA Map of Radon Zones [43]

[44] notes that the typical uranium content of rock and

Zone 1: predicted average indoor radon screening level greater than

the surrounding soil is between 1 and 3 ppm. Higher

4 pCi/L [picocuries per liter]

levels of uranium are often contained in rock such as

Zone 2: predicted average indoor radon screening level between 2 and

light-colored volcanic rock, granite, dark shale, and

4 pCi/L

sedimentary rock containing phosphate. Uranium levels

Zone 3: predicted average indoor radon screening level less than 2 pCi/L

as high as 100 ppm may be present in various areas of the

United States because of these rocks. The main source of

Important: Consult the EPA Map of Radon Zones document [EPA-402-R-

93-071] before using this map. This document contains information on

high-level radon pollution in buildings is surrounding

radon potential variations within counties.

uranium-containing soil. Thus, the greater the level of

uranium nearby, the greater the chances are that buildings

EPA also recommends that this map be supplemented with any available

local data to further understand and predict the radon potential of a

in the area will have high levels of indoor radon.

specific area.

Figure 5.5 demonstrates the geographic variation in radon

5-10

Indoor Air Pollutants and Toxic Materials

• differences in air pressure between the soil and the

house, with soil pressure often being higher;

• presence of openings in the house’s foundation; and

• increases in permeability around the basement

(if present).

Houses are often constructed with loose fill under a basement

slab and between the walls and exterior ground. This fill

is more permeable than the original ground. Houses

typically draw less than 1% of their indoor air from the

soil. However, houses with low indoor air pressures,

poorly sealed foundations, and several entry points for soil

air may draw up to 20% of their indoor air from the soil.

Figure 5.6. Radon Entry [30]

USGS [44] states that radon may also enter the home

through the water systems. Surface water sources typically

the radon gas directly or the daughter products. The

contain little radon because it escapes into the air. In

simplest devices are passive, require no electricity, and

larger cities, radon is released to the air by municipal

include a charcoal canister, charcoal liquid scintillation

processing systems that aerate the water. However, in

device, alpha tract detector, and electret ion detectors [47].

areas where groundwater is the main water supply for

All of these devices, with the exception of the ion

communities, small public systems and private wells are

detector, can be purchased in hardware stores or by mail.

typically closed systems that do not allow radon to escape.

The ion detector generally is only available through

Radon then enters the indoor air from showers, clothes

laboratories. These devices are inexpensive, primarily used

washing, dishwashing, and other uses of water. Figure 5.6

for short-term testing, and require little to no training.

shows typical entry points of radon.

Active devices, however, need electrical power and include

continuous monitoring devices. They are customarily

Health risks of radon stem from its breakdown into

more expensive and require professionally trained testers

“radon daughters,” which emit high-energy alpha

for their operation. Figure 5.7 shows examples of the

particles. These progeny enter the lungs, attach

charcoal tester (a; left) and the alpha tract detector (b; right).

themselves, and may eventually lead to lung cancer. This

exposure to radon is believed to contribute to between

After testing and evaluation by a professional, it may be

15,000 and 21,000 excess lung cancer deaths in the

necessary to lower the radon levels in the structure. The

United States each year. The EPA has identified levels

Pennsylvania Department of Environmental Protection

greater than 4 picocuries per liter as levels at which

[48] states that in most cases, a system with pipes and a

remedial action should be taken. Approximately 1 in

fan is used to reduce radon. This system, known as a subslab

15 homes nationwide have radon above this level,

depressurization system, requires no major changes to the

according to the U.S. Surgeon General’s recent advisory

home. The cost typically ranges from $500 to $2,500 and

[46]. Smokers are at significantly higher risk for radon-

averages approximately $1,000, varying with geographic

related lung cancer.

region. The typical mitigation system usually has only one

pipe penetrating through the basement floor; the pipe also

Radon in the home can be measured either by the

may be installed outside the house. The Connecticut

occupant or by a professional. Because radon has no odor

Department of Public Health [49] notes that it is more

or color, special devices are used to measure its presence.

cost effective to include radon-resistant techniques while

Radon levels vary from day to day and season to season.

constructing a building than to install a reduction system

Short-term tests (2 to 90 days) are best if quick results are

in an existing home. Inclusion of radon-resistant

needed, but long-term tests (more than 3 months) yield

techniques in initial construction costs approximately

better information on average year-round exposure.

$350 to $500 [50]. Figure 5.8 shows examples of radon-

Measurement devices are routinely placed in the lowest

resistant construction techniques.

occupied level of the home. The devices either measure

Healthy Housing Reference Manual

5-11

rodents, mosquitoes, and other pests that integrates

inspection, monitoring, treatment, and evaluation, with

special emphasis on the decreased use of toxic agents.

However, all pest management options, including natural,

biologic, cultural, and chemical methods, should be

considered. Those that have the least impact on health

and the environment should be selected. Most household

pests can be controlled by eliminating the habitat for the

pest both inside and outside, building or screening them

out, eliminating food and harborage areas, and safely

using appropriate pesticides if necessary.

Figure 5.7. Home Radon Dectectors [31]

EPA [51] states that 75% of U.S. households used at least

A passive radon-resistant system has five major parts:

one pesticide indoors during the past year and that 80% of

most people’s exposure to pesticides occurs indoors.

1. A layer of gas-permeable material under the

Measurable levels of up to a dozen pesticides have been

foundation.

found in the air inside homes. Pesticides used in and

around the home include products to control insects

2. The foundation (usually 4 inches of gravel).

(insecticides), termites (termiticides), rodents (rodenticides),

fungi (fungicides), and microbes (disinfectants). These

3. Plastic sheeting over the foundation, with all

products are found in sprays, sticks, powders, crystals,

openings in the concrete foundation floor sealed

balls, and foggers.

and caulked.

Delaplane [52] notes that the ancient Romans killed

4. A gas-tight, 3- or 4-inch vent pipe running from

insect pests by burning sulfur and controlled weeds with

under the foundation through the house to the roof.

salt. In the 1600s, ants were controlled with mixtures of

honey and arsenic. U.S. farmers in the late 19th century

5. A roughed-in electrical junction box for the future

used copper actoarsenite (Paris green), calcium arsenate,

installation of a fan, if needed.

nicotine sulfate, and sulfur to control insect pests in field

These features create a physical barrier to radon entry.

crops. By World War II and afterward, numerous

The vent pipe redirects the flow of air under the

pesticides had been introduced, including DDT, BHC,

foundation, preventing radon from seeping into the house.

aldrin, dieldrin, endrin, and 2,4-D. A significant factor

with regard to these pesticides used in and around the

Pesticides

home is their impact on children. According to a 2003

Much pesticide use could be reduced if integrated pest

EPA survey, 47% of all households with children under

management (IPM) practices were used in the home.

the age of 5 years had at least one pesticide stored in an

IPM is a coordinated approach to managing roaches,

unlocked cabinet less than 4 feet off the ground. This is

within easy reach of children. Similarly, 74% of

households without children under the age of 5 also

stored pesticides in an unlocked cabinet less than 4 feet

off the ground. This issue is significant because 13% of all

pesticide poisoning incidents occur in homes other than

the child’s home. The EPA [53] notes a report by the

American Association of Poison Control Centers

indicating that approximately 79,000 children were

involved in common household pesticide poisonings or

exposures.

The health effects of pesticides vary with the product.

However, local effects from most of the products will be

on eyes, noses, and throats; more severe consequences,

such as on the central nervous system and kidneys and on

Figure 5.8. Radon-resistant Construction [50]

5-12

Indoor Air Pollutants and Toxic Materials

cancer risks, are possible. The active and inert ingredients

• do not place rodent or insect baits where small

of pesticides can be organic compounds, which can

children have access to them;

contribute to the level of organic compounds in indoor

air. More significantly, products containing cyclodiene

• use child-resistant packaging properly by closing

pesticides have been commonly associated with

the container tightly after use;

misapplication. Individuals inadvertently exposed during

this misapplication had numerous symptoms, including

• assure that other caregivers for children are aware

headaches, dizziness, muscle twitching, weakness, tingling

of the potential hazards of pesticides;

sensations, and nausea. In addition, there is concern that

these pesticides may cause long-term damage to the liver

• teach children that pesticides are poisons and

and the central nervous system, as well as an increased

should not be handled; and

cancer risk. Cyclodiene pesticides were developed for use

as insecticides in the 1940s and 1950s. The four main

• keep the local Poison Control Center telephone

cyclodiene pesticides—aldrin, dieldrin, chlordane, and

number available.

heptachlor—were used to guard soil and seed against

insect infestation and to control insect pests in crops.

Toxic Materials

Outside of agriculture they were used for ant control;

Asbestos

farm, industrial, and domestic control of fleas, flies, lice,

Asbestos, from the Greek word meaning “inextinguishable,”

and mites; locust control; termite control in buildings, fences,

refers to a group of six naturally occurring mineral fibers.

and power poles; and pest control in home gardens. No

Asbestos is a mineral fiber of which there are several

other commercial use is permitted for cyclodiene or

types: amosite, crocidiolite, tremolite, actinolite,

related products. The only exception is the use of

anthrophyllite, and chrysotile. Chrysotile asbestos, also

heptachlor by utility companies to control fire ants in

known as white asbestos, is the predominant commercial

underground cable boxes.

form of asbestos. Asbestos is strong, flexible, resistant to

heat and chemical corrosion, and insulates well. These

An EPA survey [53] revealed that bathrooms and kitchens

features led to the use of asbestos in up to 3,000 consumer

are areas in the home most likely to have improperly stored

products before government agencies began to phase it

pesticides. In the United States, EPA regulates pesticides under

out in the 1970s because of its health hazards. Asbestos

the pesticide law known as the Federal Insecticide, Fungicide,

has been used in insulation, roofing, siding, vinyl floor

and Rodenticide Act. Since 1981, this law has required

tiles, fireproofing materials, texturized paint and

most residential-use pesticides to bear a signal word such

soundproofing materials, heating appliances (such as

as “danger” or “warning” and to be contained in child-

clothes dryers and ovens), fireproof gloves, and ironing

resistant packaging. This type of packaging is designed to

boards. Asbestos continues to be used in some products,

prevent or delay access by most children under the age of

such as brake pads. Other mineral products, such as talc

5 years. EPA offers the following recommendations for

and vermiculite, can be contaminated with asbestos.

preventing accidental poisoning:

The health effects of asbestos exposure are numerous and

varied. Industrial studies of workers exposed to asbestos in

• store pesticides away from the reach of children in

factories and shipyards have revealed three primary health

a locked cabinet, garden shed, or similar location;

risk concerns from breathing high levels of asbestos fibers:

lung cancer, mesothelioma (a cancer of the lining of the

• read the product label and follow all directions

chest and the abdominal cavity), and asbestosis (a condition in

exactly, especially precautions and restrictions;

which the lungs become scarred with fibrous tissue).

The risk for all of these conditions is amplified as the

• remove children, pets, and toys from areas before

number of fibers inhaled increases. Smoking also

applying pesticides;

enhances the risk for lung cancer from inhaling asbestos

fibers by acting synergistically. The incubation period (from

• if interrupted while applying a pesticide, properly

time of exposure to appearance of symptoms) of these

close the package and assure that the container is

diseases is usually about 20 to 30 years. Individuals who

not within reach of children;

develop asbestosis have typically been exposed to high

levels of asbestos for a long time. Exposure levels to

• do not transfer pesticides to other containers that

asbestos are measured in fibers per cubic centimeter of air.

children may associate with food or drink;

Most individuals are exposed to small amounts of asbestos

Healthy Housing Reference Manual

5-13

in daily living activities; however, a preponderance of

Common products that contained asbestos in the past

them do not develop health problems. According to the

and conditions that may release fibers include the following:

Agency for Toxic Substances and Disease Registry

(ATSDR), if an individual is exposed, several factors

•

Steam pipes, boilers, and furnace ducts insulated

determine whether the individual will be harmed [54].

with an asbestos blanket or asbestos paper tape.

These factors include the dose (how much), the duration

These materials may release asbestos fibers if

(how long), and the fiber type (mineral form and

damaged, repaired, or removed improperly.

distribution). ATSDR also states that children may be

more adversely affected than adults [54]. Children breathe

•

Resilient floor tiles (vinyl asbestos, asphalt, and

differently and have different lung structures than adults;

rubber), the backing on vinyl sheet flooring, and

however, it has not been determined whether these

adhesives used for installing floor tile. Sanding

differences cause a greater amount of asbestos fibers to

tiles can release fibers, as may scraping or sanding

stay in the lungs of a child than in the lungs of an adult.

the backing of sheet flooring during removal.

In addition, children drink more fluids per kilogram of

body weight than do adults and they can be exposed

•

Cement sheet, millboard, and paper used as

through asbestos-contaminated drinking water. Eating

insulation around furnaces and wood-burning

asbestos-contaminated soil and dust is another source of

stoves. Repairing or removing appliances may

exposure for children. Certain children intentionally eat

release asbestos fibers, as may cutting, tearing,

soil and children’s hand-to-mouth activities mean that all

sanding, drilling, or sawing insulation.

young children eat more soil than do adults. Family

members also have been exposed to asbestos that was

•

Door gaskets in furnaces, wood stoves, and coal

carried home on the clothing of other family members

stoves. Worn seals can release asbestos fibers

who worked in asbestos mines or mills. Breathing asbestos

during use.

fibers may result in difficulty in breathing. Diseases

usually appear many years after the first exposure to

•

Soundproofing or decorative material sprayed on

asbestos and are therefore not likely to be seen in

walls and ceilings. Loose, crumbly, or water-

children. But people who have been exposed to asbestos

damaged material may release fibers, as will

at a young age may be more likely to contract diseases

sanding, drilling, or scraping the material.

than those who are first exposed later in life. In the small

number of studies that have specifically looked at asbestos

•

Patching and joint compounds for walls, ceilings,

exposure in children, there is no indication that younger

and textured paints. Sanding, scraping, or drilling

people might develop asbestos-related diseases more

these surfaces may release asbestos.

quickly than older people. Developing fetuses and infants

are not likely to be exposed to asbestos through the

•

Asbestos cement roofing, shingles, and siding.

placenta or breast milk of the mother. Results of animal

These products are not likely to release asbestos

studies do not indicate that exposure to asbestos is likely

fibers unless sawed, drilled, or cut.

to result in birth defects.

•

Artificial ashes and embers sold for use in gas-

A joint document issued by CPSC, EPA, and ALA, notes

fired fireplaces in addition to other older

that most products in today’s homes do not contain

household products such as fireproof gloves,

asbestos. However, asbestos can still be found in products

stove-top pads, ironing board covers, and certain

and areas of the home. These products contain asbestos

hair dryers.

that could be inhaled and are required to be labeled as

•

Automobile brake pads and linings, clutch facings,

such. Until the 1970s, many types of building products

and gaskets.

and insulation materials used in homes routinely

contained asbestos. A potential asbestos problem both

Homeowners who believe material in their home may be

inside and outside the home is that of vermiculite. According

asbestos should not disturb the material. Generally,

to the USGS [55], vermiculite is a claylike material that

material in good condition will not release asbestos fibers,

expands when heated to form wormlike particles. It is

and there is little danger unless the fibers are released and

used in concrete aggregate, fertilizer carriers, insulation,

inhaled into the lungs. However, if disturbed, asbestos

potting soil, and soil conditioners. This product ceased

material may release asbestos fibers, which can be inhaled

being mined in 1992, but old stocks may still be available.

into the lungs. The fibers can remain in the lungs for a

5-14

Indoor Air Pollutants and Toxic Materials

long time, increasing the risk for disease. Suspected

asbestos material is damaged extensively and cannot be

asbestos-containing material should be checked regularly

otherwise repaired. Removal is complex and must be done

for damage from abrasions, tears, or water. If possible,

only by a contractor with special training. Improper

access to the area should be limited. Asbestos-containing

removal of asbestos material may create more of a

products such as asbestos gloves, stove-top pads, and

problem than simply leaving it alone.

ironing board covers should be discarded if damaged or

worn. Permission and proper disposal methods should be

Lead

obtainable from local health, environmental, or other

Many individuals recognize lead in the form often seen in

appropriate officials. If asbestos material is more than

tire weights and fishing equipment, but few recognize its

slightly damaged, or if planned changes in the home

various forms in and around the home. The Merriam-

might disturb it, repair or removal by a professional is

Webster Dictionary [56] defines lead as “a heavy soft malleable

needed. Before remodeling, determine whether asbestos

ductile plastic but inelastic bluish white metallic element

materials are present.

found mostly in combination and used especially in pipes,

cable sheaths, batteries, solder, and shields against

Only a trained professional can confirm suspected

radioactivity.” Lead is a metal with many uses. It melts easily

asbestos materials that are part of a home’s construction. This

and quickly. It can be molded or shaped into thin sheets

individual will take samples for analysis and submit them

and can be drawn out into wire or threads. Lead also is

to an EPA-approved laboratory.

very resistant to weather conditions. Lead and lead

compounds are toxic and can present a severe hazard to

If the asbestos material is in good shape and will not be

those who are overexposed to them. Whether ingested or

disturbed, the best approach is to take no action and

inhaled, lead is readily absorbed and distributed

continue to monitor the material. If the material needs

throughout the body.

action to address potential exposure problems, there are

two approaches to correcting the problem: repair and removal.

Until 1978, lead compounds were an important component

of many paints. Lead was added to paint to promote

Repair involves sealing or covering the asbestos material.

adhesion, corrosion control, drying, and covering. White

Sealing or encapsulation involves treating the material

lead (lead carbonate), linseed oil, and inorganic pigments

with a sealant that either binds the asbestos fibers together

were the basic components for paint in the 18th and 19th

or coats the material so fibers are not released. This is an

centuries, and continued until the middle of the 20th century.

approach often used for pipe, furnace, and boiler

Lead was banned by CPSC in 1978. Lead-based paint was

insulation; however, this work should be done only by a

used extensively on exteriors and interior trim-work, window

professional who is trained to handle asbestos safely.

sills, sashes, window frames, baseboards, wainscoting,

Covering (enclosing) involves placing something over or

doors, frames, and high-gloss wall surfaces, such as those

around the material that contains asbestos to prevent release

found in kitchens and bathrooms. The only way to determine

of fibers. Exposed insulated piping may be covered with a

which building components are coated with lead paint is

protective wrap or jacket. In the repair process, the

through an inspection for lead-based paint. Almost all

approach is for the material to remain in position

painted metals were primed with red lead or painted with

undisturbed. Repair is a less expensive process than is removal.

lead-based paints. Even milk (casein) and water-based

paints (distemper and calcimines) could contain some

With any type of repair, the asbestos remains in place.

lead, usually in the form of hiding agents or pigments.

Repair may make later removal of asbestos, if necessary,

Varnishes sometimes contained lead. Lead compounds also

more difficult and costly. Repairs can be major or minor.

were used as driers in paint and window-glazing putty.

Both major and minor repairs must be done only by a

Lead is widespread in the environment. People absorb

professional trained in methods for safely handling asbestos.

lead from a variety of sources every day. Although lead

has been used in numerous consumer products, the most

Removal is usually the most expensive and, unless

important sources of lead exposure to children and others

required by state or local regulations, should be the last

today are the following:

option considered in most situations. This is because

removal poses the greatest risk for fiber release. However,

• contaminated house dust that has settled on

removal may be required when remodeling or making

horizontal surfaces,

major changes to the home that will disturb asbestos

material. In addition, removal may be called for if

• deteriorated lead-based paint,

Healthy Housing Reference Manual

5-15

• contaminated bare soil,

for children to be exposed to lead. Other sources of

exposure have included imported vinyl miniblinds,

• food (which can be contaminated by lead in the

crayons, children’s jewelry, and candy. In 2004, increases

air or in food containers, particularly lead-

in lead in water service pipes were observed in Washington,

soldered food containers),

D.C., accompanied by increases in blood lead levels in

children under the age of 6 years who were served by the

• drinking water (from corrosion of plumbing

water system [58].

systems), and

In some cases, children swallow nonfood items such as

• occupational exposure or hobbies.

paint chips. These may contain very large amounts of lead,

particularly in and around older houses that were painted

Federal controls on lead in gasoline, new paint, food

with lead-based paint. Many studies have verified the

canning, and drinking water, as well as lead from industrial air

effect of lead exposure on IQ scores in the United States.

emissions, have significantly reduced total human exposure

The effects of lead exposure have been reviewed by the

to lead. The number of children with blood lead levels above

National Academy of Sciences [59].

10 micrograms per deciliter (µg/dL), a level designated as

showing no physiologic toxicity, has declined from

Generally, the tests for blood lead levels are from drawn

1.7 million in the late 1980s to 310,000 in 1999-2002.

blood, not from a finger-stick test, which can be unreliable if

This demonstrates that the controls have been effective,

performed improperly. Units are measured in micrograms

but that many children are still at risk. CDC data show

per deciliter and reflect the 1991 guidance from the Centers

that deteriorated lead-based paint and the contaminated

of Disease Control [60]:

dust and soil it generates are the most common sources of

exposure to children today. HUD data show that the

• Children: 10 µg/dL (level of concern)—find

number of houses with lead paint declined from 64 million

source of lead;

in 1990 to 38 million in 2000 [57].

• Children: 15 µg/dL and above—environmental

Children are more vulnerable to lead poisoning than are

intervention, counseling, medical monitoring;

adults. Infants can be exposed to lead in the womb if

their mothers have lead in their bodies. Infants and

• Children: 20 µg/dL and above—medical treatment;

children can swallow and breathe lead in dirt, dust, or

sand through normal hand-to-mouth contact while they

• Adults: 25 µg/dL (level of concern)—find source

play on the floor or ground. These activities make it easier

of lead; and

Action Levels for Lead

Lead in paint. Differing methods report results in differing units. Lead is considered a potential hazard if

above the following levels, but can be a hazard at lower levels if improperly handled. Below are the current

action levels identified by HUD [62] and EPA (40 CFR Part 745):

Lab analysis of samples:

5,000 milligram per kilogram (mg/kg) or 5,000 parts per million (ppm)

0.5% lead by weight.

X-ray fluorescence:

1 milligram per square centimeter (mg/cm2)

Lead in dust:

Lead in soil:

Floors, 40 micrograms per square foot (µg/ft2)

High-contact bare play areas: 400 ppm

Window sills, 250 µg/ft2

Other yard areas: 1,200 ppm

Window troughs, 400 µg/ft2 (clearance only)

5-16

Indoor Air Pollutants and Toxic Materials

• Adults: 50 µg/dL—Occupational Safety and

available by calling 1-800-424-LEAD. Do-it-yourself test

Health Administration (OSHA) standard for

kits are commercially available; however, these kits do not

medical removal from the worksite.

tell you how much lead is present, and their reliability at

detecting low levels of lead has not been determined.

Adults are usually exposed to lead from occupational

Professional testing for lead in paint is recommended.

sources (e.g., battery construction, paint removal) or at

The recommended sampling method for dust is the

home (e.g., paint removal, home renovations).

surface wet wipe. Dust samples are collected from

In 1978, CPSC banned the use of lead-based paint in

different surfaces, such as bare floors, window sills, and

residential housing. Because houses are periodically

window wells. Each sample is collected from a measured

repainted, the most recent layer of paint will most likely

surface area using a wet wipe, which is sent to a

not contain lead, but the older layers underneath

laboratory for testing. Risk assessments can be fairly low-

probably will. Therefore, the only way to accurately

cost investigations of the location, condition, and severity

determine the amount of lead present in older paint is to

of lead hazards found in house dust, soil, water, and

have it analyzed.

deteriorating paint. Risk assessments also will address

other sources of lead from hobbies, crockery, water, and

It is important that owners of homes built before 1978 be

work environments. These services are critical when

aware that layers of older paint can contain a great deal of

owners are seeking to implement measures to reduce

lead. Guidelines on identifying and controlling lead-based

suspected lead hazards in housing and day-care centers or

paint hazards in housing have been published by HUD [61].

when extensive rehabilitation is planned.

Controlling Lead Hazards

HUD has published detailed protocols for risk

The purpose of a home risk assessment is to determine,

assessments and inspections [61].

through testing and evaluation, where hazards from lead

warrant remedial action. A certified inspector or risk

It is important from a health standpoint that future tenants,

assessor can test paint, soil, or lead dust either on-site or

painters, and construction workers know that lead-based

in a laboratory using methods such as x-ray fluorescence

paint is present, even under treated surfaces, so they can

(XRF) analyzers, chemicals, dust wipe tests, and atomic

take precautions when working in areas that will generate

absorption spectroscopy. Lists of service providers are

lead dust. Whenever mitigation work is completed, it is

Definitions Related to Lead

Deteriorated lead-based paint: Paint known to contain lead above the regulated level that shows signs of

peeling, chipping, chalking, blistering, alligatoring, or otherwise separating from its substrate.

Dust removal: The process of removing dust to avoid creating a greater problem of spreading lead particles;

usually through wet or damp collection and use of HEPA vacuums.

Hazard abatement: Long-term measures to remove the hazards of lead-based paint through replacement of

building components, enclosure, encapsulation, or paint removal.

Interim control: Short-term methods to remove lead dust, stabilize deteriorating painted surfaces, treat

friction and impact surfaces that generate lead dust, and repaint surfaces. Maintenance can ensure that

housing remains lead-safe.

Lead-based paint: Any existing paint, varnish, shellac, or other coating that is equal to or greater than

1.0 milligrams per square centimeter (mg/cm2) or greater than 0.5% by weight (5,000 ppm, 5,000

micrograms per gram [µg/g], or 5,000 milligrams per kilogram [mg/kg]). For new paint, CPSC has

established 0.06% as the maximum amount of lead allowed in new paint. Lead in paint can be measured by

x-ray fluorescence analyzers or laboratory analysis by certified personnel and approved laboratories.

Risk assessment: An on-site investigation to determine the presence and condition of lead-based paint,

including limited test samples and an evaluation of the age, condition, housekeeping practices, and uses of a

residence.

Healthy Housing Reference Manual

5-17

important to have a clearance test using the dust wipe

state laws generally support the reasonable control of lead-

method to ensure that lead-laden dust generated during

based paint hazards through a variety of treatments,

the work does not remain at levels above those established

ranging from modified maintenance to selective substrate

by the EPA and HUD. Such testing is required for

removal. The key to protecting children, workers, and the

owners of most housing that is receiving federal financial

environment is to be informed about the hazards of lead,

assistance, such as Section 8 rental housing. A building or

to control exposure to lead dust and lead in soil and lead

housing file should be maintained and updated whenever

paint chips, and to follow existing regulations.

any additional lead hazard control work is completed.

Owners are required by law to disclose information about

The following summarizes several important regulations

lead-based paint or lead-based paint hazards to buyers or

that affect lead-hazard reduction projects. Owners should

tenants before completing a sales or lease contract [62].

be aware that regulations change, and they have a

responsibility to check state and local ordinances as well.

All hazards should be controlled as identified in a

Care must be taken to ensure that any procedures used to

risk assessment.

release lead from the home protect both the residents and

workers from lead dust exposure.

Whenever extensive amounts of lead must be removed

from a property, or when methods of removing toxic

Residential Lead-Based Paint Hazard Reduction Act of

substances will affect the environment, it is extremely

1992, Title X [62]. Part of the Housing and Community

important that the owner be aware of the issues surrounding

Development Act of 1992 (Public Law 102-550) [63]. It

worker safety, environmental controls, and proper disposal.

established that HUD issue Guidelines for the Evaluation

Appropriate architectural, engineering, and environmental

and Control of Lead-Based Paint Hazards in Housing [61]

professionals should be consulted when lead hazard

to outline risk assessments, interim controls, and

projects are complex.

abatement of lead-based paint hazards in housing. Title X

calls for the reduction of lead in federally supported

Following are brief explanations of the two approaches for

housing. It outlines the federal responsibility toward its

controlling lead hazard risks. These controls are

own residential units and the need for disclosure of lead

recommended by HUD in HUD Guidelines for the

in residences, even private residences, before a sale. Title X

Evaluation and Control of Lead-Based Paint Hazards in

also required HUD to establish regulations for federally

Housing [61], and are summarized here to focus on

assisted housing (24 CFR Part 35) and EPA to establish

special considerations for historic housing:

standards for lead in paint, dust, and soil, as well as

standards for laboratory accreditation (40 CFR Part 745).

Interim Controls. Short-term solutions include thorough

EPA’s residential lead hazard standards are available at

dust removal and thorough washdown and cleanup, paint

http://www.epa.gov/lead/leadhaz.htm.

film stabilization and repainting, covering of lead-

contaminated soil, and informing tenants about lead

Interim Final Rule on Lead in Construction (29 Code of

hazards. Interim controls require ongoing maintenance

Federal Regulations [CFR] 1926.62) [64]. Issued by

and evaluation.

OSHA, these regulations address worker safety, training,

and protective measures. The regulations are based in part

Hazard Abatement. Long-term solutions are defined as

on personal-air sampling to determine the amount of lead

having an expected life of 20 years or more and involve

dust exposure to workers.

permanent removal of hazardous paint through chemicals,

heat guns, or controlled sanding or abrasive methods;

State Laws. States generally have the authority to regulate

permanent removal of deteriorated painted features

the removal and transportation of lead-based paint and

through replacement; removal or permanent covering of

the generated waste through the appropriate state

contaminated soil; and the use of enclosures (such as

environmental and public health agencies. Most

drywall) to isolate painted surfaces. The use of specialized

requirements are for mitigation in the case of a lead-

encapsulant products can be considered as permanent

poisoned child, for protection of children, or for oversight

abatement of lead.

to ensure the safe handling and disposal of lead waste.

When undertaking a lead-based paint reduction program,

Reducing and controlling lead hazards can be successfully

it is important to determine which laws are in place that

accomplished without destroying the character-defining

may affect the project.

features and finishes of historic buildings. Federal and

5-18

Indoor Air Pollutants and Toxic Materials

Local Ordinances. Check with local health departments,

prevent rot. Numerous studies show that arsenic sticks to

poison control centers, and offices of housing and

children’s hands when they play on treated wood, and it is

community development to determine whether any laws

absorbed through the skin and ingested when they put

require compliance by building owners. Determine

their hands in their mouths. Although most uses of

whether projects are considered abatements and will

arsenic wood treatments were phased out by 2004, an

require special contractors and permits.

estimated 90% of existing outdoor structures are made of

arsenic-treated wood [65].

Owner’s Responsibility. Owners are ultimately

responsible for ensuring that hazardous waste is properly

In a study conducted by the University of North Carolina

disposed of when it is generated on their own sites.

Environmental Quality Institute in Asheville, wood

Owners should check with their state government to

samples were analyzed and showed that

determine whether an abatement project requires a

certified contractor. Owners should establish that the

• Older decks and play sets (7 to 15 years old) that

contractor is responsible for the safety of the crew, to

were preserved with chromated copper arsenic

ensure that all applicable laws are followed, and that

expose people to just as much arsenic on the

transporters and disposers of hazardous waste have

wood surface as do newer structures (less than

liability insurance as a protection for the owner. The

1 year old). The amount of arsenic that testers

owner should notify the contractor that lead-based paint

wiped off a small area of wood about the size of a

may be present and that it is the contractor’s

4-year-old’s handprint typically far exceeds what

responsibility to follow appropriate work practices to

EPA allows in a glass of water under the Safe

protect workers and to complete a thorough cleanup to

Drinking Water Act standard. Figure 5.9 shows a

ensure that lead-laden dust is not present after the work is

safety warning label placed on wood products.

completed. Renovation contractors are required by EPA

to distribute an informative educational pamphlet

• Arsenic in the soil from two of every five

(Protect Your Family from Lead in Your Home) to

backyards or parks tested exceeded EPA’s

occupants before starting work that could disturb lead-

Superfund cleanup level of 20 ppm.

based paint (http://www.epa.gov/lead/

leadinfo.htm#remodeling).

Arsenic is not just poisonous in the short term, it causes

cancer in the long term. Arsenic is on EPA’s short list of

Arsenic

chemicals known to cause cancer in humans. According to the

Lead arsenate was used legally up to 1988 in most of the

National Academy of Sciences, exposure to arsenic causes

orchards in the United States. Often 50 applications or

lung, bladder, and skin cancer in humans, and is suspected as

more of this pesticide were applied each year. This toxic

a cause of kidney, prostate, and nasal passage cancer.

heavy metal compound has accumulated in the soil

around houses and under the numerous orchards in the

country, contaminating both wells and land. These

orchards are often turned into subdivisions as cities

expand and sprawl occurs. Residues from the pesticide

lead arsenate, once used heavily on apple, pear, and other

orchards, contaminate an estimated 70,000 to 120,000 acres

in the state of Washington alone, some of it in areas

where agriculture has been replaced with housing,

according to state ecology department officials and others.

Lead arsenate, which was not banned for use on food

crops until 1988, nevertheless was mostly replaced by the

pesticide dichlorodiphenyltrichloroethane (DDT) and its

derivatives in the late 1940s. DDT was banned in the

United States in 1972, but is used elsewhere in the world.

Figure 5.9. Arsenic Label

For more than 20 years, the wood industry has infused

green wood with heavy doses of arsenic to kill bugs and

Healthy Housing Reference Manual

5-19

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Washington, DC: US Department of Housing

Healthy Housing Reference Manual

5-23

Chapter 6: Housing Structure

“The Palace of Fine Arts in Mexico City has sunk more

Figure 6.1 shows a typical house being built and

than 10 feet into the ground since it was built 60 years

inspected today and includes a terminology key. Both the

ago and the most noticeable effect is that the grand stone

figure and the key are available in an interactive format

stairway has disappeared and the entrance is now at

in the glossary on the U.S. Inspect Web site [1].

street level.”

Figure 6.2 shows a typical house built between 1950 and

C.B. Crawford,

1980 and also includes a terminology key. The figures

Canadian Building Digest

show the complexity and the numerous components of a

home. These components form the vocabulary that is

Introduction

necessary to discuss housing structure inspection issues.

The principal function of a house is to provide

protection from the elements. Our present society,

Key to Figure 6.1 (New Housing Terminology)

however, requires that a home provide not only shelter,

1. Ash dump (see 35)—A door or opening in the

but also privacy, safety, and reasonable protection of our

firebox that leads directly to the ash pit, through

physical and mental health. A living facility that fails to

which the ashes are swept after the fire is burned out.

offer these essentials through adequately designed and

All fireboxes are not equipped with an ash dump.

properly maintained interiors and exteriors cannot be

termed “healthful housing.”

2. Attic space—The open space within the attic area.

In this chapter, the home is considered in terms of the

3. Backfill—The material used to refill an excavation

parts that have a bearing on its soundness, state of repair,

around the outside of a foundation wall or pipe

and safety. These are some of the elements that the

trench.

housing inspector must examine when making a

thorough housing inspection.

4. Baluster—One of a series of small pillars that is

Figure 6.1. Housing Structure Terminology, Typical House Being Built Today [1]

Healthy Housing Reference Manual

6-1

attached to and runs between the stairs and the

and contains one or more flues and extends above the

handrails. The spacing between the balusters should

roofline.

be less than 4 inches to prevent small children from

getting stuck between the balusters. Balusters are

13. Chimney cap—The metal or masonry protective

considered a safety item and provide an additional

coveringat the top of the chimney that seals the

barrier.

chimney shaft from water entry between the chimney

enclosure and the flue tiles.

Baseboard trim—Typically a wood trim board that is

placed against the wall around the perimeter of a

14. Chimney flues—The space or channel in a chimney

room next to the floor. The intent is to conceal the

that carries off the smoke and other combustion gases

joint between the floor and wall finish.

to the outside air. Most homes will have a terra cotta

tile flue or a metal flue.

Basement window—A window opening installed in

the basement wall. Basement windows are

15. Collar beam/tie—A horizontal piece of framing

occasionally below the finish grade level and will be

lumber that provides intermediate support for

surrounded on the exterior by a window well.

opposite rafters. They are usually located in the

middle to upper third portion of the rafters. It is also

Blind or shutter—A lightweight frame in the form of

known as a collar beam or collar brace.

a door located on each side of a window. They are

most commonly constructed of wood (solid or

16. Concrete slab floor—Typically approximately

louvered panels) or plastic. Originally they were

4 inches thick, the concrete slab floor provides a

designed to close and secure over the windows for

number of uses. It creates a solid level surface to walk

security and foul weather. Most shutters now are more

and work on. It provides a separation between the

likely decorative pieces that are secured to the house

grade/soil and a potentially livable area. It also

beside the windows.

provides lateral compression resistance for the

foundation walls, preventing soil pressure from

Bridging—Small pieces of wood or metal strapping

outside the foundation from pushing the foundation

placed in an X-pattern between the floor joists at

walls and footings inward.

midspan to prevent the joists from twisting and

squeaking and to provide reinforcement and

17. Corner brace—Diagonal braces placed at the corners

distribution of stress.

of framed walls to stiffen them and provide extra strength.

Building paper/underlayment—Building material,

18. Cornice—An overhang of a pitched roof at the eave

usually a felt paper that is used as a protective barrier

line that usually consists of a fascia board, a soffit, and

against air and moisture passage from the area

any appropriate moldings or vents.

beneath the flooring as well as providing a

movement/noise isolator in hardwood flooring.

19. Cornice molding—The individual pieces of wood

trim that are applied to the cornice area at the eaves.

10. Ceiling joist—A horizontally placed framing

members at the ceiling of the top-most living space of

20. Door casing/trim—The finish trim details around the

a house that provides a platform to which the finished

perimeter of the door on the interior finished wall.

ceiling material can be attached.

21. Door frame/jamb—The top and sides of the door to

11. Chair rail (not shown)—Decorative trim applied

include the wall framing as well as the actual door

around the perimeter of a room such as a formal

frame and trim.

dining room or kitchen/breakfast nook at the

approximate same height as the back of a chair. It is

22. Downspout—A pipe, usually of metal or vinyl, that is

sometimes used as a cap trim for wainscoting (see

connected to the gutters and is used to carry the roof-

wainscoting).

water runoff down and away from the house.

12. Chimney—A masonry or in more modern

23. Downspout gooseneck—Segmented section of

construction wood framed enclosure that surrounds

downspout that is bent at a radius to allow the

6-2

Housing Structure

downspout to be attached to the house and to follow

32. Finish flooring (not shown)—The final floor covering

the bends and curves of the eaves and ground.

inside the living space of a house. The most common

types of finishes are carpeting; hardwood flooring;

24. Downspout shoe—The bottom downspout

ceramic, composite, or laminate stone tile; parquet

gooseneck that directs the water from the downspout

panels; or vinyl sheet flooring.

to the extension or splash block at the grade.

33. Finished grade line—A predetermined line indicating the

25. Downspout strap—Strap used to secure the

proposed elevation of the ground surface around a

downspout to the side of the house.

building.

26. Drain tile—A tube or cylinder that is normally

34. Firebox—The cavity in the open face of the fireplace

installed around the exterior perimeter of the

in which the fire is maintained. The firebox leads

foundation footings that collects and directs ground

directly to the fireplace flue. The firebox is constructed of

water away from the foundation of the house. The tile

fire or refractory brick set in fireclay or reinforced

can be individual sections of clay or asphalt tubing or,

mortar in traditional masonry fireplaces. The firebox

in more recent construction, a perforated-plastic drain

may also be constructed of metal or ceramic-coated

tile that is approximately 4 inches in diameter. The

metal panels in more modern prefabricated fireplaces.

drain tile leads either towards a sump or to an exterior

The walls of the firebox are usually slanted toward the

discharge away from the house.

living space both to direct smoke up toward the flue

and to reflect heat into the room.

27. Entrance canopy—A small overhanging roof that

shelters the front entrance.

35. Fireplace cleanout door—The access door to the ash

pit beneath the fireplace. On a fireplace that is located

28. Entrance stoop—An elevated platform constructed of

inside the house, the cleanout door is usually located

wood framing or masonry at the front entry that

in the lowest accessible level of the house such as the

allows visitors to stand above or out of the elements.

basement or crawl space. On a fireplace that is located

The platform should be wide enough to allow

at the outside of the house, the cleanout door will be

someone to stand on the platform while opening an

located at the exterior of the chimney. Not all

outward swinging door such as a storm door even if

fireplaces are equipped with a cleanout door.

one is not present.

36. Fireplace hearth—The inner or outer floor of a

29. Exterior siding—The decorative exterior finish on a

fireplace, usually made of brick, tile, or stone.

house. Its primary function is to protect the shell of

the house from the elements. The choice of siding

37. Flashing (not shown)—The building component

materials varies widely to include wood, brick, metal,

used to connect and cover portions of a deck, roof, or

vinyl, concrete, stucco, and a variety of manufactured

siding material to another surface such as a wall, a

compositions such as compressed wood, compressed

chimney, a vent pipe, or anywhere that runoff is

cellulose (paper), fiber-reinforced cement, and

heavy or where two dissimilar materials meet. The

synthetic stucco.

flashing is mainly intended to prevent water entry and

is usually made of rubber, tar, asphalt, or various metals.

30. Fascia—The visible flat front board that caps the

rafter tail ends and encloses the overhang under the

38. Floor joists—The main subfloor framing members

eave that runs along the roof edge. The gutter is

that support the floor span. Joists are usually made of

usually attached at this location.

engineered wood I-beams or 2×8 or larger lumber.

31. Fascia/rake board—The visible flat front board that

39. Foundation footing—The base on which the

caps the rafter tail ends and encloses the overhang

foundation walls rests. The foundation is wider than

under the eave that runs along the roof edge and at

the foundation wall to spread out the load it is

the edge of the roofing at the gables. The gutter is

bearing and to help prevent settling.

usually attached to this board at the eaves.

40. Foundation wall—The concrete block, concrete slab

or other nonwood material that extends below or

Healthy Housing Reference Manual

6-3

partly below grade, which provides support for

49. Mantel—The ornamental or decorative facing around

exterior walls and other structural pans of the building.

a fireplace including a shelf that is attached to the

breast or backing wall above the fireplace.

41. Framing studs—A 2×4 or 2×6 vertical framing

member used to construct walls and partitions,

50. Moisture/vapor barrier—A nonporous material, such

usually spaced 12 to 24 inches apart.

as plastic or polyethylene sheeting, that is used to

retard the movement of water vapor into walls and

42. Gable framing—The vertical and horizontal framing

attics and prevent condensation in them. A vapor

members that make up and support the end of a building

barrier is also installed in crawl space areas to prevent

as distinguished from the front or rear side. A gable is

moisture vapor from entering up through the ground.

the triangular end of an exterior wall above the eaves.

51. Newel post—The post at the top and bottom of the

43. Garage door—The door for the vehicle passage into

handrails and anywhere along the stair run that

the garage area. Typical garage doors consist of

creates a directional change in the handrails is called

multiple jointed panels of wood, metal, or fiberglass.

the newel post. The newel post is securely anchored

into the underlying floor framing or the stair stringer

44. Girder—A large beam supporting floor joists at the same

to provide stability to the handrails.

level as the sills. A larger or principal beam used to support

concentrated loads at isolated points along its length.

52. Reinforcing lath—A strip of wood or metal attached

to studs and used as a foundation for plastering,

45. Gravel fill—A bed of coarse rock fragments or

slating or tiling. Lath has been replaced by gypsum

pebbles that is laid atop the existing soil before

board in most modern construction.

pouring the concrete slab. The gravel serves a dual

purpose of breaking surface tension on the concrete

53. Ridge board/beam—The board placed on edge at the

slab and providing a layer that interrupts capillary

top-most point of the roof framing, into which the

action of subsurface moisture from reaching the

upper ends of the rafters are joined or attached.

concrete slab. Typically, a polyethylene sheeting will

be installed between the gravel fill and the concrete

54. Roofing—The finished surface at the top of the house

slab for further moisture proofing.

that must be able to withstand the effects of the

elements (i.e., wind, rain, snow, hail, etc.). A wide

46. Gutter—A channel used for carrying water run-off.

variety of materials are available, including asphalt

Usually located at the eaves of a house and connected

shingles, wood shakes, metal roofing, ceramic and

to a downspout. The primary purpose of the gutters

concrete tiles, and slate, with asphalt shingles making

and downspouts is to carry roof water run-off as far

up the bulk of the material used.

away from the house as possible.

55. Roof rafters—Inclined structural framing members

47. Insulation—A manufactured or natural material that

that support the roof, running from the exterior wall

resists heat flow that is installed in a house’s shell to

the to the ridge beam. Rafters directly support the

keep the heat in a house in the winter and the

roof sheathing and create the angle or slope of the roof.

coolness in the house in the summer. The most

common form of insulation is fiberglass, whether in

56. Roof sheathing—The material used to cover the

batts or blown-in material, along with cellulose, rigid

outside surface of the roof framing to provide lateral

foam boards, sprayed-in foam, and rock wool.

and rack support to the roof, as well as to provide a

nailing surface for the roofing material. This material

48. Jack/king stud—The framing stud, sometimes called

most commonly consists of plywood OSB or

the trimmer, that supports the header above a

horizontally laid wood boards.

window, door, or other opening within a bearing wall.

Depending on the size of the opening, there may be

57. Sidewalk—A walkway that provides a direct, all-

several jack studs on either side of the opening.

weather approach to an entry. The sidewalk can be

constructed of poured concrete, laid stone, concrete

pavers, or gravel contained between borders or curbs.

6-4

Housing Structure

58. Sill plate—The horizontal wood member that is

68. Termite shield—A metal flashing that is installed

anchored to the foundation masonry to provide a

below the sill plate that acts as a deterrent to keep

nailing surface for floors or walls built above.

termites from reaching the sill plate.

59. Silt fabric—A porous fabric that acts as a barrier

69. Top plate—The topmost horizontal framing members

between the backfilled soil (see backfill) and the gravel

of a framed wall. Most construction practices require

surrounding the drain tile. This barrier prevents soil

the top plate to be doubled in thickness.

particles from blocking the movement of groundwater

to the drain tile.

70. Wainscoting—The wooden paneling of the lower

part of an interior wall up to approximately waist-

60. Soffit/lookout block—Rake cross-bracing between

height or between 36 and 48 inches from the floor.

the fly rafters and end gable rafters that the soffit is

nailed to.

71. Wall insulation—A manufactured or natural material

that resists heat flow that is installed in a house’s shell

61. Stair rail—A sturdy handhold and barrier that follows

to keep the heat in a house in the winter and the

the outside, and sometimes inside, perimeter of the

coolness in the house in the summer. Fiberglass batts

stairs. The stair rail is used to prevent falls and to

are the most common form of wall insulation.

provide a means of additional support when walking

up or down the stairs.

72. Wall sheathing—The material used to cover the

outside surface of the wall framing that provides lateral

62. Stair riser—The vertical boards that close the space

and shear support to the wall as well as a nailing

between each stair tread on a set of stairs (see stair

surface for the exterior siding.

stringer and stair tread).

73. Window casing/trim—The finish trim details around

63. Stair stringer—The supporting members in a set of

the perimeter of the window on the interior finished wall.

stairs that are cut or notched to accept the individual

treads and risers (see stair riser and stair tread).

74. Window cripple—Short studs placed between the

header and a top plate or between a sill and sole plate.

64. Stair tread—The horizontal board in a stairway that

is walked upon (see stair riser and stair stringer).

75. Window frame/jamb—The top and sides of the

65. Subfloor—Boards or plywood, installed over joists,

window, to include the wall framing and the actual

on which the finish floor rests.

window frame and trim.

66. Support post—A vertical framing member usually

76. Window header—A beam placed perpendicular to

designed to carry or support a beam or girder. In

wall studs above doors, windows, or other openings to

newer construction a metal lally (pronounced “lolly”)

carry the weight of structural loads above the window

column is commonly used, as well as 4×4- or 6×6-

or door.

inch wood posts.

77. Window sash—The framework that holds the glass in

67. Tar—Otherwise known as asphalt, tar is a very thick,

a door or window.

dark brown/black substance that is used as a sealant or

waterproofing agent. It is usually produced naturally

78. Window well (not shown)—An excavation around a

by the breakdown of animal and vegetable matter that

basement window that prevents the surrounding soils

has been buried and compressed deep underground.

from collapsing into the window. The window well

Tar is also manufactured—a hydrocarbon by-product

surround is normally constructed of formed

or residue that is left over after the distillation of

corrugated galvanized metal, built-up masonry, or

petroleum. It is commonly used as a sealant or patch for

pressure-treated wood.

roof penetrations, such as plumbing vents and chimney

flashing. Tar is also used as a sealer on concrete and

masonry foundation walls before they have been

backfilled.

Healthy Housing Reference Manual

6-5

Key to Figure 6.2 (Old Housing Terminology)

6. Ash dump—A trap door to let the ashes drop to a pit

Fireplace

below, where they may be easily removed.

1. Chimney—A vertical masonry shaft of reinforced

concrete or other approved noncombustible, heat

7. Cleanout door—The door to the ash pit or the bottom of

resisting material enclosing one or more flues. It

a chimney through which the chimney can be cleaned.

removes the products of combustion from solid,

liquid or gaseous fuel.

8. Chimney breast—The inside face or front of a

fireplace chimney.

2. Flue liner—The flue is the hole in the chimney. The

liner, made of terra cotta or metal, protects the brick

9. Hearth—The floor of a fireplace that extends into the

from harmful smoke gases.

room for safety purposes.

3. Chimney cap—This top is generally of concrete. It

Roof

protects the brick from weather.

10. Ridge—The top intersection of two opposite

adjoining roof surfaces.

4. Chimney flashing—Sheet metal flashing provides a

tight joint between chimney and roof.

11. Ridge board—The board that follows along under

the ridge.

5. Firebrick—An ordinary brick cannot withstand the

heat of direct fire, and so special firebrick is used to

12. Roof rafters—The structural members that support

line the fireplace. In newer construction, fireplaces are

the roof.

constructed of prefabricated metal inserts.

Figure 6.2. Housing Structure and Terminology, Typical House Built Between 1950 and 1980 [2]

6-6

Housing Structure

13. Collar beam—Not a beam at all; this tie keeps the

27. Plate—The board laid across the top ends of the

roof from spreading and connects similar rafters on

studs to hold them even and tight.

opposite sides of the roof.

28. Corner bracing—Diagonal strips to keep the frame

14. Roof insulation—An insulating material (usually rock

square and plumb.

wool or fiberglass) in a blanket form placed between

the roof rafters to keep a house warm in the winter

29. Sheathing—The first layer of outer wall covering

and cool in the summer.

nailed to the studs.

15. Roof sheathing—The boards that provide the base

30. Joist—The structural members or beams that hold up

for the finished roof. In newer construction, roof

the floor or ceiling, usually 2×10s or 2×12s spaced

sheathing is composed of sheets of plywood, or

16 inches apart.

oriented strand board (OSB).

31. Bridging—Cross-bridging or solid. Members at the

16. Roofing—The wood, asphalt or asbestos shingles—or

middle or third points of joist spans to brace one to

tile, slate, or metal—that form the outer protection

the next and to prevent them from twisting.

against the weather.

32. Subflooring—Typically plywood or particle wood

17. Cornice—A decorative element made of molded

that is laid over the joists.

members, usually placed at or near the top of an

exterior or interior wall.

33. Flooring paper—A felt paper laid on the rough floor

to stop air infiltration and, to some extent, noise.

18. Gutter—The trough that gathers rainwater from a roof.

34. Finish flooring—Hardwood, of tongued and grooved

19. Downspout—The pipe that leads the water down

strips, carpet, or vinyl products (tile, linoleum).

from the gutter.

35. Building paper or sheathing—Paper or plasticized

20. Storm sewer tile—The underground pipe that

material placed outside the sheathing, not as a vapor

receives the water from the downspouts and carries it

barrier, but to prevent water and air from leaking in.

to the sewer. In newer construction, plastic-type

Building paper is also used as a tarred felt under

material have replaced tile.

shingles or siding to keep out moisture or wind.

21. Gable—The triangular end of a building with a

36. Beveled siding—Sometimes called clapboards, with a

sloping roof.

thick butt and a thin upper edge lapped to shed

water. In newer construction, vinyl, aluminum, or

22. Barage board—The fascia or board at the gable just

fiber cement siding and stucco are more prevalent.

under the edge of the roof.

37. Wall insulation—A blanket of wool or reflective foil

23. Louvers—A series of slanted slots arranged to keep

placed inside the walls.

out rain, yet allow ventilation.

38. Metal lath—A mesh made from sheet metal onto

Walls and Floors

which plaster or other composite surfacing materials

24. Corner post—The vertical member at the corner of

can be applied. In newer construction, plaster

the frame, made up to receive inner and outer covering

sheetrock 4-×8-foot sheets have replaced lath.

materials.

Foundation and Basement

25. Studs—The vertical wood members of the house,

39. Finished grade line—The top of the ground at the

usually 2×4s at minimum and spaced every 16 inches.

foundation.

26. Sill—The board that is laid first on the foundation,

40. Foundation wall—The wall of poured concrete

and on which the frame rests.

(shown) or concrete blocks that rests on the footing

and supports the remainder of the house.

Healthy Housing Reference Manual

6-7

41. Termite shield—A metal baffle to prevent termites

57. Stair tread—The horizontal part of a step that the

from entering the frame.

foot hits when climbing up or down the stairs.

42. Footing—The concrete pad that carries the entire

58. Stair riser—The vertical board connecting one tread

weight of the house upon the earth.

to the next.

43. Footing drain tile—A pipe with cracks at the joints,

59. Stair stringer—The sloping board that supports the

or perforated plastic pipe to allow underground water

ends of the steps.

to drain away before it gets into the basement.

60. Newel—The post that terminates the railing.

44. Basement floor slab—The 4- or 5-inch layer of

concrete that forms the basement floor.

61. Stair rail—The bar used for a handhold when using

the stairs.

45. Gravel fill—Placed under the slab to allow drainage

and to guard against a damp floor.

62. Balusters—Vertical rods or spindles supporting a rail.

46. Girder—A main beam upon which floor joists rest.

Foundation

Usually of steel, but also of wood.

The word “foundation” is used to mean

47. Backfill—Earth, once dug out, that has been replaced

• construction below grade, such as footings, cellar,

and tamped down around the foundation.

or basement;

48. Areaway—An open space to allow light and air to a

• the composition of the earth on which the

window. Also called a light well.

building rests; and

49. Area wall—The wall, of metal or concrete, that forms

• special construction, such as pilings and piers used

the open area.

to support the building.

Windows and Doors

The foundation bed may be composed of solid rock,

50. Window—An opening in a building for admitting

sand, gravel, or unconsolidated sand or clay. Rock, sand,

light and air. It usually has a pane or panes of glass

or gravel are the most reliable foundation materials.

and is set in a frame or sash that is generally movable

Figure 6.3 shows the three most common foundations for

for opening and shutting.

homes. Unconsolidated sand and clay, though found in

many sections of the country, are not as desirable for

51. Window frame—The lining of the window opening.

foundations because they are subject to sliding and

settling [1]. Capillary breaks have been identified as a key

52. Window sash—The inner frame, usually movable,

way of reducing moisture incursion in new construction [3].

that holds the glass.

The footing distributes the weight of the building over a

53. Lintel—The structural beam over a window or door

sufficient area of ground to ensure that the foundation

opening.

walls will stand properly. Footings are usually concrete;

however, in the past, wood and stone have been used.

54. Window casing—The decorative strips surrounding a

Some older houses were constructed without footings.

window opening on the inside.

Although it is usually difficult to determine the condition

Stairs and Entry

of a footing without excavating the foundation, a footing

55. Entrance canopy—A roof extending over the

in a state of disrepair or lack of a footing will usually be

entrance door.

indicated either by large cracks or by settlement in the

foundation walls. This type of crack is called a “Z” crack.

56. Furring—Falsework or framework necessary to bring

the outer surface level to the inner surface.

Foundation wall cracks are usually diagonal, starting from

the top, the bottom, or the end of the wall (Figure 6.4).

6-8

Housing Structure

Cracks that do not extend to at least one edge of the wall

Holes in the foundation

may not be caused by foundation problems. Such wall

walls are common in many

cracks may be due to other structural problems and

old houses. These holes

should also be reported.

may be caused by missing

bricks or blocks. Holes and

The foundation walls support the weight of the structure

cracks in a foundation wall

and transfer this weight to the footings. The foundation

are undesirable because

walls may be made of stone, brick, concrete, or concrete

they make a convenient

blocks. The exterior should be moisture proofed with

entry for rats and other

either a membrane of waterproof material or a coating of

rodents and also indicate

portland cement mortar. The membrane may consist of

the possibility of further

plastic sheeting or a sandwich of standard roofing felt

structural deterioration.

joined and covered with tar or asphalt. The purpose of

Basement problems are a

waterproofing the foundation and walls is to prevent

major complaint of

water from penetrating the wall material and leaving the

homeowners [4-9].

basement or cellar walls damp.

Concrete is naturally

porous (12%-18% air).

When it cures, surplus

water creates a network of

interconnected capillaries.

These pores let in liquid

water, water vapor, and

radon gas. Like a sponge,

Figure 6.4. Foundation Cracks [4]

concrete draws water from

several feet away. As concrete ages, the pores get bigger as

a result of freezing, thawing, and erosion.

Concrete paints, waterproofing sealers, or cement coatings

are a temporary fix. They crack or peel and cannot stop

gases such as water vapor and radon.

Damp basement air spreads mold and radon through the

house. Efflorescence (white powder stains) and musty

odors are telltale signs of moisture problems.

Basement remodeling traps invisible water vapor, causing

mold and mildew. Most basements start leaking within

10 to 15 years. The basement walls and floors should be

sealed and preserved before they deteriorate. The basement

floor should be concrete placed on at least 6 inches of

gravel. The gravel distributes groundwater movement

under the concrete floor, reducing the possibility of the

water penetrating the floor. A waterproof membrane, such as

plastic sheeting, should be laid before the concrete is

placed for additional protection against flooding and the

infiltration of radon and other gases.

The basement floor should be gradually, but uniformly,

sloped from all directions toward a drain or a series of

drains. These drains permit the basement or cellar to drain if

it becomes flooded.

Figure 6.3. Foundation [3]

Healthy Housing Reference Manual

6-9

Water or moisture marks on the floor and walls are signs

placed beneath the slab. Moisture tests should be done to

of ineffective waterproofing or moisture proofing. Cellar

determine the suitability of the slab before installing

doors, hatchways, and basement windows should be

wood products. A vapor barrier equivalent to 4- or 6-mil

weather-tight and rodent-proof. A hatchway can be inspected

polyethylene should be installed on top of the slab to further

by standing at the lower portion with the doors closed; if

protect the wood products and the residents of the home.

daylight can be seen, the door needs to be sealed or repaired.

Wall and Ceiling Vapor Barriers

Vapor Barriers

Wall and ceiling vapor barriers should go on the heated

Crawl Space Vapor Barriers

side of the insulation and are necessary in cold climates.

Throughout the United States, even in desert areas, there

Water vapor flows from areas of high pressure (indoors in

is moisture in the ground from groundwater being

winter) through the wall to an area of low pressure

absorbed. Even in an apparently dry crawl space, a large

(outdoors in winter). People and their pets produce

amount of water is entering. The moisture is drying out

amazing quantities of water vapor by breathing. Additional

as fast as it is entering, which causes high moisture levels

moisture in considerable quantities is created in the home

in the crawl space and elsewhere in the house. A solid

from everyday activities such as washing clothes, cooking,

vapor barrier is recommended in all crawl spaces and

and personal hygiene. The purpose of the vapor barrier is

should be required if moisture problems exist [10]. This

to prevent this moisture from entering the wall and freezing,

vapor barrier, if properly installed, also reduces the

then draining, causing damage. In addition, wet insulation has

infiltration of radon gas. Of course, if the moisture is

very little insulating value. Insulation with the vapor

coming from above ground, a vapor barrier will collect

barrier misplaced will allow the vapor to condense in the

and hold the moisture. Therefore, any source of moisture

insulation and then freeze. In cold climates, this ice can

must be found and eliminated. The source may be as

actually build up all winter and run out on the floor in

obvious as sweating pipes, or may be more difficult to

the spring. Such moisture buildup blisters paint, rots

spot, such as condensation on surfaces. The solution can

sheathing, and destroys the insulating value of insulation.

be as simple as applying insulation to exposed sections of

the piping or complex enough to require power exhaust

House Framing

fans and the addition of insulation and vapor barriers.

Many types of house-framing systems are found in

various sections of the country; however, most framing

The more common causes of moisture problems in a new

systems include the elements described in this section.

home are moisture trapped within the structure during

construction and a continuing source of excess moisture

Foundation Sills

from the basement, crawl space, or slab. To resolve this

The purpose of the sill is to provide support or a bearing

potential problem, 6-mil plastic sheets should be laid as

surface for the outside walls of the building. The sill is the

vapor barriers over the entire crawl space floor. The sheets

first part of the frame to be placed and rests directly on

should overlap each other by at least 6 inches and should

the foundation wall. It is often bolted to the foundation

be taped in place. The plastic should extend up the

wall by sill anchors. In many homes, metal straps are

perimeter walls by about 6 inches. The plastic sheets

cemented into the foundation wall that are bent around

should be attached to the interior walls of the crawl space

and secured to the sill. It is good practice to protect the

with mastic or batten strips. All of the perimeter walls

sill against termites by extending the foundation wall to at

should be insulated, and insulation should be between the

least 18 inches above the ground and using a noncorroding

joists at the top of the walls. Vents, which may need to be

metal shield continuously around the outside top of the

opened in the late spring and closed in the fall, should

foundation wall.

not be blocked. If not properly managed, moisture

originating in the crawl space can cause problems with

Flooring Systems

wood flooring and create many biologic threats to health

The flooring system is composed of a combination of

and property. A properly placed vapor barrier can prevent

girders, joists, subflooring, and finished flooring that may

or reduce problem moisture from entering the home.

be made up of concrete, steel, or wood. Joists are laid

perpendicular to the girders, at about 16 inches on center, and

Vapor Barriers for Concrete Slab Homes

the subflooring is attached to them. If the subfloor is wood, it

Strip flooring and related products should be protected

may be nailed, glued, or screwed at either right angles or

from moisture migration by a slab. Proper on-grade or

diagonally to the joists. Many homes are built with wood

above-grade construction requires that a vapor barrier be

I-joists or trusses rather on than solid wood joists.

6-10

Housing Structure

In certain framing systems, a girder supports the joists

There are two types of walls or partitions: bearing and

and is usually a larger section than the joists it supports.

nonbearing. A bearing wall is constructed at right angles

Girders are found in framing systems where there are no

to support the joists. A nonbearing wall, or partition, acts

interior bearing walls or where the span between bearing

as a screen or enclosure; hence, the headers in it are often

walls is too great for the joists. The most common application

parallel to the joists of the floor above.

of a girder is to support the first floor. Often a board known

as a ledger is applied to the side of a wood girder or beam

In general, studs, like joists, are spaced 16 inches on

to form a ledge for the joists to rest upon. The girder, in

center. In light construction, such as garages and summer

turn, is supported by wood posts or steel “lally columns”

cottages, wider spacing on studs is common.

that extend from the cellar or basement floor to the girder.

Openings for windows or doors must be framed in studs.

Studs

This framing consists of horizontal members (headers)

For years, wall studs were composed of wood and were

and vertical members (trimmers or jack studs).

2×4 inches; but, with the demand for greater energy

efficiency in homes, that standard no longer holds true.

Because the vertical spaces between studs can act as flues

Frame studs up to 6 inches wide are used to increase the

to transmit flames in the event of a fire, fire stops are

area available for placing insulation material. The

important in preventing or retarding fire from spreading

increased size in the studs allow for larger spaces between

through a building by way of air passages in walls, floors,

joists.

and partitions. Fire stops are wood obstructions placed

between studs or floor joists to block fire from spreading

There are now alternatives to conventional wood studs,

in these natural flue spaces.

specifically, insulated concrete forms, structural insulated

panels, light-gauge steel, and combined steel and wood

Interior Walls

[11-13]. The advantages of light-gauge steel include the

Many types of materials are used for covering interior

following:

walls and ceilings, but the principal type is drywall. The

generic term “drywall” is typically used when talking

• weighs 60% less than equivalent wood units and

about gypsum board. It is also called wallboard or referred

has greater strength and durability;

to by the brand name Sheetrock. Gypsum board is a sheet

material composed of a gypsum filler faced with paper. In

• is impervious to termites and other damage-

drywall construction, gypsum boards are fastened to the

causing pests;

studs either vertically or horizontally and then painted.

The edges along the length of the sheet are slightly

• stays true and does not warp;

recessed to receive joint cement and tape.

• is noncombustible; and

Drywall finish, composed of gypsum board, is a material

that requires little, if any, wait for application. Other

• is recyclable.

drywall finishes include plywood, fiberboard, or wood in

various sizes and forms. Plaster was once quite popular for

The disadvantages of steel include these:

interior walls. Plaster is a mixture (usually of lime, sand,

and water) applied in two or three coats to lath to form a

• steel is an excellent thermal conductor and

hard-wall surface. A plaster finish requires a base on

requires additional external insulation;

which plaster can be spread. Wood lath at one time was

the plaster base most commonly used, but today gypsum-

• as a new product, it is unfamiliar to craftsmen,

board lath is more popular. Gypsum lath may be

engineers, and code officials; and

perforated to improve the bond and thus lengthen the

time the plaster can remain intact when exposed to fire.

• a different type of construction tools are required.

Building codes in some cities require that gypsum lath be

perforated. Expanded-metal lath also may be used as a

The combined steel and wood framing system includes

plaster base. Expanded-metal lath consists of sheet metal

light-gauge steel studs with 6-inch wooden stud pieces

slit and expanded to form openings to hold the plaster.

attached to the top and bottom to allow easy attachment

Plaster is applied over the base to a minimum thickness of

to traditional wood frame materials.

½ inch. Because wood-framing members may dry after

Healthy Housing Reference Manual

6-11

the house is completed, some shrinkage can be expected,

Windows

which, in turn, may cause plaster cracks to develop

The six general classifications of windows (Figure 6.6) are

around openings and in corners. Strips of lath embedded

as follows [1]:

in the plaster at these locations prevent cracks. Bathrooms

have unique moisture exposure problems and local code

• Double-hung sash windows that move up or

approved cement board should be used around bath and

down, balanced by weights hung on chains, ropes,

shower enclosures.

or springs on each side;

Stairways

• Casement sash windows that are hinged at the side

The purpose of stairway dimension standards is to ensure

and can be hung so they will swing out or in;

adequate headroom and uniformity in riser and tread size.

• Awning windows that usually have two or more

Interior stairways (Figure 6.5) should be no less than

glass panes that are hinged at the top and swing

44 inches wide. The width of a stairway may be reduced

out horizontally;

to 36 inches when permitted by local or state code in

one- and two-family dwellings. Stairs with closed risers

• Sliding windows that usually have two or more

should have maximum risers of 8¼ inches and minimum

glass panes that slide past one another on a

treads of 9 inches plus 1 inch nosing. Basement stairs are

horizontal track;

often constructed with open risers. These stairs should

have maximum risers of 8¼ inches and minimum treads

• Fixed windows that are generally for increased

of 9 inches plus 1-inch nosing. The headroom in all parts

light entry and decorative effect; and

of the stair enclosure should be no less than 80 inches.

Dimensions of exterior stairways should be the same as

• Skylight windows for increased room illumination

those of interior stairways, except that the headroom

and decoration that can be built to open.

requirement does not apply.

The principal parts of a window, shown in three-

Staircases should have handrails that are between 1¼ and

dimensional view in Figure 6.7 and face-on and side view

25/8 inches wide, particularly if the staircases have more

in Figure 6.8, are the following:

than four steps. Handrails should be shaped so they can

be readily grasped for safety and placed so they are easily

accessible. Handrails should be 41/8 inches from the wall

and be 34 to 38 inches above the leading edge of the

stairway treads. Handrails should not end in any manner

or have projections that can snag clothing.

Figure 6.6. Classifications of Windows [1]

Figure 6.5. Interior Stairway [4]

6-12

Housing Structure

Drip cap—A separate piece of wood projecting over the

layers of glass with a low

top of the window; a component of the window casing.

emissivity film suspended

The drip cap protects against moisture.

between them. Triple-

glazed windows have

Window trough—The cut or groove in which the sash of

advantages where

the window slides or rests.

extremes in weather and

temperature are the

Window sill—The shelf on the bottom edge of a

norm. They also can

window, either a projecting part of the window frame or

reduce sound

the bottom of the wall recess that the window fits into. The

transmission to a greater

sill contains the trough and protects against moisture.

degree than can single- or

double-glazed windows.

Recent technological advancements—new materials,

coatings, design, and construction features—make it

Doors

possible to choose windows that allow you to balance

There are many styles of

winter heating and summer cooling needs without

doors both for exterior

sacrificing versatility or style. To ensure that windows,

and interior use. Exterior

doors, or skylights selected are appropriate for the region

doors must, in addition

in which they are to be installed, Energy Star

to offering privacy,

Certification labels include a climate region map.

protect the interior of the

structure from the

Some window glass is made of tempered glass to resist

elements. Various parts of

breakage. Some windows are made of laminated glass,

a door are the same as the

which resists breakage, but if broken produces glass shards

corresponding parts of a

too small to cause injury [14]. The glazing, or glass, can

window. A door’s

be a solid glass sheet (single glazed) or have two layers of

function is best

Figure 6.8. Window Details [3]

glass (double glazed) separated by a spacer. Air trapped

determined by the material

between the glass layers provides some insulation value.

from which it is made, how it looks, and how it operates.

Triple-glazed windows have three pieces of glass, or two

When doors are used for security, they are typically made

from heavy materials and have durable, effective locks and

hinges. A door that lets in light or allows people to look

out onto the yard, such as a sliding glass door or a french

door, will have multiple panes (also called lights) or be made

almost completely of glass.

Houses have many exterior and interior door options.

Exterior doors are typically far sturdier than interior doors

and need to be weather tight and ensure security for the

home. Exterior doors are also more decorative than most

interior doors and may cost a considerable amount.

Typical exterior doors include front entry doors, back

doors, french doors, dutch doors, sliding glass doors,

patio doors, and garage doors.

French doors and sliding doors are examples of the two

primary ways doors open. French doors swing on hinges;

sliding doors glide along a track. Some doors, such as

dutch doors, have tops and bottoms that swing open

independently.

Most doors are made of wood or materials made to look

like wood. Fiberglass composite and steel doors often have

Figure 6.7. Three Dimensional View of a Window [1]

Healthy Housing Reference Manual

6-13

polymer or vinyl coatings embossed with wood grain;

• A sticker on all newly manufactured garage door

some even have cellulose-based coatings that can be

openers warning consumers of the potential

stained like wood doors. Wood doors are made from

entrapment hazard. The sticker is to be placed near

every kind of wood imaginable, hardwoods being the

the wall-mounted control button.

most durable and elegant. Wood doors insulate better

than glass; composite and steel doors provide even more

The variety of exterior door systems has increased

insulation and durability, as well as better security than

significantly over the past 5 to 10 years. Many combine

does wood.

several different materials to make a realistic, if not actual

wood, door that provides both beauty and enhanced security.

Garage Doors

Garage doors open in almost any configuration needed

Exterior House Doors

for the design of the home. Installing most garage doors is

Exterior door frames are ordinarily of softwood plank,

complex and dangerous enough that only a building

with the side rabbitted to receive the door in the same

professional should attempt it. Garage doors often include

way as casement windows. At the foot is a sill, made of

very strong springs that can come loose and severely

hardwood or other material, such as aluminum, to

injure the unsuspecting installer. Garage door springs are

withstand the wear of traffic and sloped down and out to

under extreme tension because of the heavy loads they

shed water. Doors often come equipped with door sweeps

must lift, which makes them dangerous to adjust. A

to conserve energy.

garage door may suffer from any of several problems. The

most common problem is that the door becomes difficult

The four primary categories of modern exterior doors are

to lift and lower. This may be something that can be

steel, fiberglass, composites, and wood.

resolved with simple adjustments, or it may be more

serious. If the door is connected to an electric opener, the

Steel—The most common exterior door sold today is

opener mechanism can be disconnected from the door by

steel. Humidity will not cause a steel door to warp or twist.

pulling the release cord or lever. If the door then works

Steel doors often have synthetic wood-grain embossed

manually, the problem is with the electric opener. A door

finishes that accept stain. Just about every steel exterior door

that seems unusually hard to lift may have a problem with

is filled with some type of foam. This foam allows the doors

spring tension. Wood doors should be properly painted or

to achieve R-values almost five times that of an ordinary

stained both outside and inside. If only the outside of a

wood door. Metal is often used as a veneer frame. In general,

garage door is finished, the door may warp and moisture

the horizontal members are called rails and the vertical

may cause the paint to peel.

members are called stiles. Every door has a top and

bottom rail, and some may have intermediate rails. There

Rules issued by the Consumer Product Safety

are always at least two stiles, one on each side of the door.

Commission on December 3, 1992, specify entrapment

protection requirements for garage doors [15].

Fiberglass—The second most frequently selected exterior

door is fiberglass. Fiberglass doors are similar to steel doors,

The rules require that residential garage door openers

but tend to be much more resistant to denting. (Steel

contain one of the following:

doors can be dented quite easily.) Fiberglass doors also are

stainable and have rich, realistic wood graining. Fiberglass

• An external entrapment protection device, such as

doors are insulated with foam and have high R-values.

an electric eye that sees an object obstructing the

door without having actual contact with the

Composite materials—The third most common exterior

object. A door-edge sensor is a similar device. The

door is made of composite materials. These doors often

door-edge sensor acts much like the door-edge

are of two materials blended together. Their composite

sensors on elevator doors.

fiber-reinforced core can be twice as strong as wood. This

composite core will not rot, warp, or twist when subjected

• A constant contact control button, which is a

to high levels of humidity.

wall-mounted button requiring a person to hold

in the control button continuously for the door to

Wood—The last major category of doors is wood. Solid

close completely. If the button is released before

wood doors range from inexpensive to true works of art.

the door closes, the door reverses and opens to the

Their downside is that they can warp and bow if not sealed

highest position.

properly from humidity and will then fit poorly in their frames.

6-14

Housing Structure

Other types of wooden doors are described below.

with an integral or attached stop against which the

door closes.

•

Batten doors are often found on older homes.

They are made of boards nailed together in

Roof Framing

various ways. The simplest is two layers nailed to

Rafters

each other at right angles, usually with each layer

One of a series of structural roof members spanning from

at 45° to the vertical. Another type of batten door

an exterior beam or a ridge board. Rafters serve the same

consists of vertical boards nailed at right angles to

purpose for the roof as joists do for floors, that is,

several (two to four) cross strips called ledgers,

providing support for sheathing and roofing material.

with diagonal bracing members nailed between

They are typically placed on 16-inch centers.

the ledgers. If vertical members corresponding to

ledgers are added at the sides, the verticals are

Collar Beam

called frames. Batten doors are often found in

Collar beams are ties between rafters on opposite sides of

cellars and other places where appearance is not a

the roof. If the attic is to be used for rooms, the collar

factor and economy is desired.

beam may double as the ceiling joist.

•

Solid flush doors are perfectly flat, usually on both

Purlin

sides, although occasionally they are made flush

A purlin is the horizontal member that forms the support

on one side and are paneled on the other. Flush

for the rafters at the intersection of the two slopes of a

doors sometimes are solid planking, but they are

gambrel roof.

commonly veneered and possess a core of small

pieces of white pine or other wood. These pieces

Ridge Board

are glued together with staggered end joints. Along

A ridge board is a horizontal member that forms a lateral

the sides, top, and bottom are glued ¾ inch edge

tie to make rafters secure.

strips of the same wood, used to create a smooth

surface that can be cut or planed. The front and

Hip

back faces are then covered with a 1/8-inch to

A hip is like a ridge, except that it slopes. It is the intersection

¼-inch layer of veneer. Solid flush doors may be

of two adjacent, rather than two opposite, roof planes.

used on both the interior and exterior.

Roof Sheathing

•

Hollow-core doors, like solid flush doors, are

The manner in which roof sheathing is applied depends

perfectly flat; but, unlike solid doors, the core

upon the type of roofing material. Roof boards may vary

consists mainly of a grid of crossed wooden slats

from tongue-and-groove lumber to plywood panels.

or some other type of grid construction. Faces are

three-ply plywood instead of one or two plies of

Dormer

veneer, and the surface veneer may be any species

The term “dormer window” is applied to all windows in

of wood, usually hardwood. The edges of the core

the roof of a building, whatever their size or shape.

are solid wood and are made wide enough at the

appropriate places to accommodate locks and

Roofs

butts. Doors of this kind are considerably lighter

Asphalt Shingle

than solid flush doors. Hollow-core doors are

The principal damage to asphalt shingle roofs is caused by

usually used as interior doors.

strong winds on shingles nailed close to the ridge line of

the roof. Usually the shingles affected by winds are those

Many doors are paneled, with most panels consisting of

in the four or five courses nearest the ridge and in the

solid wood or plywood, either raised or flat, although

area extending about 5 feet down from the edge or rake of

exterior doors frequently have one or more panels of glass.

the roof.

One or more panels may be used, although some have as

many as nine panels. Paneled doors may be used both on

EPDM

the interior or exterior.

Ethylene propylene diene monomer (EPDM) is a single-

ply roofing system. EPDM allows extreme structural

The frame of a doorway is the portion to which the door

movement without splitting or cracking and retains its

is hinged. It consists of two side jambs and a head jamb,

pliability in a wide range of temperatures.

Healthy Housing Reference Manual

6-15

Asphalt Built-up Roofs

Roof Flashing

Asphalt roofs may be unsurfaced (a coating of bitumen

Valleys in roofs (such as gambrel roofs, which have two

being exposed directly to the weather) or surfaced (with

pitches designed to provide more space on upper floors

slag or gravel embedded in the bituminous coating).

and are steeper on their lower slope and flatter toward the

Using surfacing material is desirable as a protection

ridge) that are formed by the junction of two downward

against wind damage and the elements. This type of roof

slopes may be open or closed. In a closed valley, the slates,

should have enough pitch to drain water readily.

tiles, or shingles of one side meet those of the other, and

the flashing below them may be comparatively narrow. In

Coal Tar Pitch Built-up Roofs

an open valley, the flashing, which may be made of zinc,

This type of roof must be surfaced with slag or gravel. A

copper, or aluminum, is laid in a continuous strip,

coal tar pitch built-up roof should always be used on a

extending 12 to 18 inches on each side of the valley, while

deck pitched less than ½ inch per foot; that is, where

the tiles or slates do not come within 4 to 6 inches of it.

water may collect and stand. This type of roof should be

The ridges built up on a sloping roof where it runs down

inspected on completion, 6 months later, and then at least

against a vertical projection, like a chimney or a skylight,

once a year, preferably in the fall. When the top coating

should be weatherproofed with flashing. Failure of roof

of bitumen shows damage or has become badly

flashing is usually due to exposed nails that have come

weathered, it should be renewed.

loose. The loose nails allow the flashing to lift, resulting

in leakage. Flashings made of lead or coated with lead

Slate Roofs

should not be used.

The most common problem with slate roofs is the

replacement of broken slates. Otherwise, slate roofs

The use of a thin, self-sticking rubber ice and water shield

normally render long service with little or no repair.

under flashings and on the edge of roofs is now common

practice. The shield helps reduce leakage and ice backup

Tile Roofs

in cold climates, preventing serious damage to this part of

Replacement of broken shingle tiles is the main

the home.

maintenance problem with tile roofs. This is one of the most

expensive roofing materials. It requires very little maintenance

Gutters and Leaders

and gives long service.

Gutters and leaders should be of noncombustible

materials and should not be made of lead, lead-coated

Copper Roofs

copper, or any other formulation containing lead. They

Usually made of 16-ounce copper sheeting and applied to

should be securely fastened to the structure and spill into

permanent structures, copper roofs require practically no

a storm sewer, not a sanitary sewer, if the neighborhood

maintenance or repair when properly installed. Proper

has one. When there is no storm sewer, a concrete or

installation allows for expansion and contraction with

stone block placed on the ground beneath the leader

changes in temperature.

prevents water from eroding the lawn. This stone block is

called a splash block. Gutters should be checked every

Galvanized Iron Roofs

spring and fall and cleaned when necessary. Gutters must

The principal maintenance for galvanized iron roofs

be placed or installed to ensure that water drainage is

involves removing rust and keeping the roof well painted.

taken away from the foundation of the house. Soil around

Leaks can be corrected by renailing, caulking, or replacing

the home should be graded in a manner that also drains

all or part of the sheet or sheets in disrepair.

the water away from the foundation of the home.

Wood Shingle Roofs

Exterior Walls and Trim

The most important factors of wood shingle roofs are their

Exterior walls are enclosure walls whose purpose is not

high pitch and exposure, the character of wood, the kind of

only to make the building weather tight, but to also allow

nails used and the preservative treatment given the

the building to dry out. In most one- to three-story

shingles. At one time these roofs were treated with

buildings they also serve as bearing walls. These walls may

creosote and coal tar preservatives. Because they are made

be made of many different materials (Figure 6.9).

from a flammable material, insurance companies

frequently have higher rates for wood shingle roofs.

Brick is often used to cover framed exterior walls. In this

situation, the brick is only one course thick and is called a

brick veneer. It supports nothing but itself and is kept

6-16

Housing Structure

from toppling by ties

because PVC is known to cause cancer in humans.

connected to the frame

Accidental fires in vinyl-sided buildings are more dangerous

wall.

because vinyl produces toxic vapors when heated.

In frame construction,

Putting It All Together

the base material of the

The next section shows a home being built by Habitat for

exterior walls is called

Humanity.

sheathing. The sheathing

material may be square-

This small, one-family home represents all of the

edge, shiplap,

processes that would also be used for a far more expensive

tongue-and-groove

and elaborate dwelling. The homebuilding demonstrated

boards, or plywood or

by the following pictures was by an industrial arts class to

oriented strand board

educate and train a new generation of construction specialists

(OSB). Sheathing, in

and homebuilders.

addition to serving as a

base for the finished

siding material, stiffens

the frame to resist sway

caused by wind. It is for

this reason that sheathing

is applied diagonally on

frame buildings. Its role

is to brace the walls

effectively to keep them

from racking.

Many types of sidings,

Figure 6.9. Wall Framing [4]

shingles, and other

exterior coverings are applied over the sheathing. Vinyl

siding; wood siding; brick, cedar, and other wood shingles

or shakes; asphalt; concrete; clapboard; common siding

The foundation trench for a new home has horizontal metal

(called bevel siding); composition siding; cement shingles;

rods, also called reinforcement rods or rebar, to increase the

strength of the concrete. After the concrete hardens, a

fiber cement (e.g., Hardiplank); and aluminum siding are

perforated pipe 4 to 6 inches in diameter is placed beside it

commonly used for exterior coverings. In older homes,

to collect water and allow it to drain away from the

asbestos-cement siding shingles can still be found as an

foundation. This pipe is the footing drain, and the poured

exterior application or underneath various types of

concrete beside it is the footer. The footing drain is

aluminum or vinyl siding.

important in removing water from the base of the home. It

also serves the secondary purpose of moisture control in the

home and provides a venting route for radon gas. The holes

Clapboard and common siding differ only in the length

dug near the legs of the workers will be filled with concrete

of the pieces. Composition siding is made of felt, grit,

and form the footer that will hold up the porch of the home.

and asphalt, which are often shaped to look like brick.

Asbestos and cement shingles, which were used until the

To assist in preventing capillary action from wicking water

early 1970s, are rigid and produce a siding that is fire-

from the foundation to the wooden structure, a polyethylene

resistant, but also a health hazard. Cedar wood shingles

sheet is placed over the footer before pouring the concrete

foundation, or building a cinderblock foundation.

and aluminum are manufactured with a backer board that

gives insulation and fire-resistant qualities. Vinyl siding is

manufactured from polyvinyl chloride (PVC), a building

material that has replaced metal as the prime material for

many industrial, commercial, and consumer products.

PVC has many years of performance as a construction

material, providing impact-resistance, rigidity, and

strength. The use of vinyl siding is not without controversy,

Healthy Housing Reference Manual

6-17

The concrete on top of the footer is leveled to establish a

Concrete will be poured into this form on top of the footer

surface for the foundation of the home. Once the footer has

to create the foundation of the home. Again, reinforcing rods

hardened, the perforated drainage pipe will be laid on the

are added to ensure that the concrete has both lateral

outside of the poured foundation wall. The reinforcing rods

strength, as well as the strength to support the home. Once

were positioned in the trench before pouring the concrete.

the concrete has hardened and becomes seasoned, the forms

will be removed to reveal the finished poured concrete

foundation over the perforated drainage pipe. Not shown is a

newer technique of using insulating polystyrene forms and

ties in a building foundation.

Foundations are not always poured concrete, but are often

Gravel fill is placed outside the finished poured concrete

cinderblock or similar materials that are cemented in place

foundation. This ensures that moisture does not stand

to form the load-bearing wall. The arrow shows the concrete

around the foundation for any time. The moisture is routed

chute delivering concrete into the form. Long poles are

to the footing drain for fast dispersal.

pushed into the freshly poured concrete to remove air

pockets that would weaken the foundation.

Care must be taken to ensure that the forms are

appropriately supported before pouring the concrete. Often

tar, plastic, or other waterproof materials are placed on the

outside of the foundation to the ground level to further

divert moisture from the house to the footing drains.

6-18

Housing Structure

A termite shield is established on top of the concrete wall

OSB subfloor, the joist supporting the floor, and the metal

(foundation) just below the sill of the home. The sill is

bridging that is used to keep the joist from twisting can be

typically made of pressure- and insecticide-treated wood to

seen from the crawl space under the home.

ensure stability and long life.

If the material used for the flooring or external sheathing of

A cinderblock foundation will be used to support the storage

the home is made of plywood or a composition that is not

shed attached to the house. Note the potential for

waterproof, the material must be protected from rain to

inadvertent sabotage of the termite shield if a shield is not

prevent deterioration and germination of mold spores. Some

installed on the top of the cinder block foundation.

glues or resins release toxic vapors for years if deterioration

is allowed to begin.

The flooring material of the

The interior wall framing is

first floor of the home is OSB

composed of studs

applied to the subfloor with

traditionally referred to as

both glue and wood screws.

2×4s. The horizontal member

Where possible, the screws

at the top of the studs is

should extend into the subfloor

called a girt or a ribbon. In

and the joist below the subfloor to prevent squeaking.

this case the builders

have used two 2×4s, placing

one on top of the other.

Because the outside walls

have used studs that are 2×6-inch boards, the girts or

ribbons on top of these are also double 2×6-inch boards.

The exterior wall

framing is composed of

studs that are 2x6-inch

boards. The horizontal

member extending from

one exterior wall to the

The joists above the first floor

other is called a girder

are connected to the central

and is a prime support

girder of the home by steel

for the second floor of the home. The larger studs in the

brackets. These brackets

exterior wall are used both for greater strength and to provide

provide a far more effective

greater energy efficiency for the home.

alternative than does

toenailing nails to hold the joists in place or to notching the

The lintels above the windows and doors distribute the

girder to hold them.

weight of the second floor and roof across the studs that are

located on each side of the openings in the frame.

Healthy Housing Reference Manual

6-19

The subroof or roof

An interior wall is

sheathing is applied from

installed to create

the bottom up with

second-floor rooms.

temporary traction boards

nailed to the subroof to

The subroof has been

allow safe installation of the

installed.

material.

The exterior wood of

The subroof is placed on the rafters up to the ridge board of

the home has been

the roof. A waterproof material will be added to the subroof

covered with plastic

before installing the final roofing material.

sheathing or a

housewrap to protect it

from moisture.

Flashing material, such

as sheet metal, is

installed at critical

locations to make sure

that water does not

enter the home where

the joints and angles of

a roof meet:

• where the dormer roof meets the roof and the walls

of the dormer meet the roof,

• where windows penetrate the walls,

A safety scaffold is standing at the rear of the home, and the

• where the vent stack penetrates the roof,

final roofing material has been applied, in addition to the

exterior vinyl siding.

• where the porch roof meets the front wall,

• skylights, and

• eaves of the house.

6-20

Housing Structure

Governments; 1998. Available from URL:

http://www.abag.ca.gov/bayarea/eqmaps/

fixit/ch5.

Crawford CB. CBD-148: foundation

measurements. Ottawa, Ontario, Canada:

National Research Council; 1972. Available from

URL: http://irc.nrc-cnrc.gc.ca/cbd/cbd148e.html.

Hamilton JJ. CBD-184: foundations on swelling

or shrinking subsoils. Ottawa, Ontario, Canada:

National Research Council; 1977. Available from

URL: http://irc.nrc-cnrc.gc.ca/pubs/

cbd/cbd184_e.html.

The front porch of the home is constructed of pressure-

treated, insect-resistant lumber. The use of such lumber

10. US Department of Housing and Urban

should be carefully evaluated with respect to what chemicals

Development. Basements and crawl spaces.

have been used and the potential for human exposure to the

treated wood. Composite wood products and plastic decking

Washington, DC: US Department of Housing

materials, collectively called Trex, are available as an

and Urban Development; 2000. Available from

alternative to pressure-treated wood. A proper hand railing

URL: http://www.hud.gov/offices/hsg/sfh/

and balusters will be installed.

ref/sfhp1-25.cfm.

References

11. Bateman BW. Light-gauge steel verses

US Inspect. Glossary of terms. Chantilly, VA: US

conventional wood framing in residential

Inspect; no date. Available from URL:

construction. J Construction Educ

http://www.usinspect.com/Glossary/glossary.asp.

1997;2(2):99-108.

Center for Disease Control. Housing construction

12. National Association of Home Builders Research

terminology. In: Basic housing inspection. Atlanta:

Center. Integrated steel/wood combination

US Department of Health and Human Services;1976.

framing. Upper Marlboro, MD: National

Association of Home Builders; no date. Available

Building Science Corporation. Read this before

from URL: http://www.toolbase.org/

you design, build, or renovate. Westford, MA:

tertiaryT.asp?DocumentID=

Building Science Corporation; 2004.

4249&CategoryID=1142.

Center for Disease Control. Basic housing

13. Steel Wood Studs. Why use steel wood studs?

inspection. Atlanta: US Department of Health

Reno, NV: Steel Wood Studs; 2001.

and Human Services; 1976.

14. Canadian Mortgage and Housing Corporation.

Wagner JD. Drying out a wet basement. New

Understanding window terminology. Ottawa,

York: This Old House Ventures, Inc.; no date.

Ontario, Canada: Canadian Mortgage and

Available from URL: http://www.thisoldhouse.com/

Housing Corporation; no date. Available from

toh/knowhow/interiors/article/

URL: http://www.cmhc-schl.gc.ca/

0,16417,220912,00.html.

en/burema/gesein/abhose/abhose_061.cfm.

Friedman D. Inspecting foundations for structural

15. US Consumer Product Safety Commission. Safety

defects. Poughkeepsie, NY: Daniel Friedman;

commission publishes Final Rules for automatic

2001. Available from URL: http://www.inspect-

garage door openers. Washington, DC: US

ny.com/structure/foundation.htm.

Consumer Product Safety Commission; 1992.

Available from URL: http://www.cpsc.gov/

Association of Bay Area Governments. Foundations:

cpscpub/prerel/prhtml93/93024.html.

section 5. Oakland, CA: Association of Bay Area

Healthy Housing Reference Manual

6-21

Chapter 7: Environmental Barriers

“The physician can bury his mistakes, but the architect can

hand, moisture seeping though basement or foundation

only advise his client to plant vines—so they should go as far

walls often is very expensive to repair. Eliminating such

as possible from home to build their first buildings.”

moisture is seldom as simple as coating the interior wall,

but often requires expert consultation and excavating

Frank Lloyd Wright

around the perimeter of the house to install or clean

New York Times, October 4, 1953

clogged footing drains. Sealing the outside of the

basement walls and coating the exterior foundation wall

Introduction

with tar or other waterproofing compounds are often the

Damaging moisture originates not only from outside a

only solutions to eliminate moisture.

home; it is created inside the home as well. Moisture is

produced by smoking; breathing; burning candles;

Moisture condensation occurs in both winter and summer.

washing and drying clothes; and using fireplaces, gas

The following factors increase the probability of

stoves, furnaces, humidifiers, and air conditioning. Leaks

condensation:

from plumbing, unvented bathrooms, dishwashers, sinks,

toilets, and garbage disposal units also create moisture

• Homes that are ineffectively insulated and are not

problems because they are not always found before water

sealed against air infiltration in cold climates can

damage or mold growth occurs. Figure 7.1 provides an

result in major moisture problems.

overview of the sources of moisture and types of air

pollutants that can enter a home.

• Cool interior surfaces such as pipes, windows, tile

floors, and metal appliances; air conditioner coils

Solving moisture problems is often expensive and time-

with poor outside drainage; masonry or concrete

consuming. The first step is to do a moisture inventory

surfaces; toilet tanks; and, in the winter, outside

to eliminate problems in their order of severity. Problems

walls and ceilings can result in moisture buildup

that are easiest and least expensive to resolve should be

from condensation. If the temperature of an

addressed first. For example, many basement leaks have

interior surface is low enough to reach the dew

been eliminated by making sure sump pumps and

point, moisture in the air will condense on it and

downspouts drain away from the house. On the other

enhance the growth of mold.

Figure 7.1. Sources of Moisture and Air Pollutants [1]

Healthy Housing Reference Manual

7-1

•

Dehumidifiers used in regions where outside

thermal efficiency, and longevity. However, all roofs have

humidity levels are normally 80% or higher have

two things in common: the need to shed moisture and

a moisture-collecting tank that should be cleaned

protect the interior from the environment.

and disinfected regularly to prevent the growth of

mold and bacteria. It is best if dehumidifiers have

When evaluating the roof of a home, the first thing to

a drain line continuously discharging directly to

observe is the roofline against the sky to see if the roof’s

the outside or into a properly plumbed trap. This

ridge board is straight and level. If the roofline is not

is also true in climates where air conditioning

straight, it could mean that serious deterioration has taken

units are used on a full-time or seasonal basis.

place in the structure of the home as a result of improper

Their cooling pans provide an excellent

construction, weight buildup, a deteriorated or broken

environment for the growth of allergenic or

ridge beam, or rotting rafters. Whatever the cause, the focus of

pathogenic organisms.

an inspection must be to locate the extent of the damage.

•

Moisture removed from clothing by clothes driers

The next area to inspect is around the flashing on the

ends up in the dryer vent if it is clogged by lint or

roof. Flashing is used around any structure that penetrates

improperly configured. Moisture buildup in this

the surface of a roof or where the roofline takes another

vent can result in mold growth and, if leakage

direction. These areas include chimneys, gas vents, attic

occurs, damage to the structure of the home. The

vents, dormers, and raised and lowered roof surfaces. One

vent over the cooking area of the kitchen also

of the best ways to locate a leak around flashing is to go

should be checked routinely for moisture or grease

into the attic and look carefully. Leaks often are

buildup.

discovered when it rains; but if it is not raining, the

underside of the roof can be examined with the attic

Roof

lights off for pinpoints of daylight.

The control of moisture in a home is of paramount

importance. It is no surprise that moisture control begins

Roofing material should lay relatively flat and should not

with the design and integrity of the roof. Many types of

wave or ripple. The roof should be checked for missing or

surfacing materials are used for roofs-stone, composition

damaged shingles, areas where flashing should be installed,

asphalt, plastic, or metal, for example. Some have

elevation changes in roof surfaces, and evidence of

relatively short lives and some, such as slate and tile, have

decomposing or displaced surfaces around the edge of the

extraordinarily long lives. As in nearly all construction

roof [1-3].

materials, tradeoffs must be made in terms of cost,

Roof Inspection

Is the roofline of the house straight?

Are there ripples or waves in the roof?

What is the condition of the gutters and downspouts?

What is the condition of the boards the gutters are attached to?

Does the flashing appear to be separated or damaged?

Is there any apparent damage in the attic or can sunlight be seen through the roof?

Is there mold or discoloration on the rafters or roof sheathing?

Is there evidence of corrosion between the gutter and downspouts and any metal roofing or

aluminum siding?

Do the downspouts route the water away from the base or foundation of the home?

10)

Are the gutters covered or free of leaves? Are they sagging or separating from the fascia?

11)

Does the gutter provide a mosquito-breeding area by holding water?

7-2

Environmental Barriers

Figure 7.3. Depth of Attic Insulation

Figure 7.2. Blown Attic Insultation

Insulation

A house must be able to breathe; therefore, air must not

be trapped inside, but must be allowed to exit the home

with its moisture. Moisture buildup in the home will lead

to both mold and bacteria growth. Figure 7.2 demonstrates

insulation blown into an attic, to a depth of approximately

12 inches (Figure 7.3). Figure 7.4 shows the area

extending from a house under the roof, known as the

soffit. The soffit is perforated so that air can flow into the

attic and up through the ridge vents to ventilate the attic.

If insulation is too thick or installed improperly, it

restricts proper air turnover in the attic and moisture or

extreme temperatures could result in mold or bacteria

growth, as well as delamination of the plywood and

particleboards and premature aging of the roof’s

subsurface and shingles.

Care also must be taken in cold climates to ensure that

the insulation has a vapor barrier and that it is installed

face down. When insulation is placed in the walls of a

home, a thin plastic vapor barrier should be placed over

Figure 7.4. Blown Attic Insultation

the insulation facing the inside of the home. The purpose

of this vapor barrier is to keep moisture produced inside

weather-resistant coating. Fire-resistant siding and roofing

the house from compromising the insulation. If the

are important in many areas where wildfires are common

barrier is not installed, warm, moist air will move through

and are required by many local building codes.

the drywall and into the insulated wall cavity. When the

air cools, moisture will condense on the fibers of the

All exterior surfaces will eventually deteriorate, regardless

insulation making it wet; and, if it is cellulose insulation,

of manufacturer warranties or claims. Leaks in the home

it will absorb and hold the moisture. Wetness reduces the

from the outside occur in many predictable locations. The

effectiveness of the insulation and provides a favorable

exterior siding or brick should be checked for cracks or

environment for the growth of bacteria and mold [4,5].

gaps in protective surfaces. Where plumbing, air vents,

electrical outlets, or communication lines extend through

Siding

an exterior wall, they should be carefully checked to

Good siding should be attractive, durable, insect- and

ensure an airtight seal around those openings. The

vermin-resistant, waterproof, and capable of holding a

exterior surface of the home has doors, windows, and

Healthy Housing Reference Manual

7-3

other openings. These openings should be caulked

such as the one in Figure 7.5, is

routinely, and the drainage gutters along the top should

an example of such a failure. This

be checked to ensure that they drain properly.

type of damage will require much

more than just a mortar patch.

Exterior surface materials include stucco, vinyl, asbestos

Buildings constructed of concrete

Figure 7.5. Brick

shingles, brick, metal (aluminum), fiber cement, exterior

block also experience footer

Structural Defect

plywood, hardwood, painted or coated wood, glass, and

failure. The damage is reason to

tile, some of which are discussed in this chapter [6,7].

not skimp when installing and inspecting the footing and

reinforces the need for appropriate concrete mix, rebar,

Fiber Cement

and footing drains.

Fiber cement siding is engineered composite-material

products that are extremely stable and durable. Fiber

Stucco

cement siding is made from a combination of cellulose

Synthetic stucco (exterior insulation and finish system;

fiber material, cement and silica sand, water, and other

EIFS) is a multilayered exterior finish that has been used

additives. Fiber cement siding is fire resistant and useful

in Europe since shortly after World War II, when

in high-moisture areas.

contractors found it to be a good repair choice for

buildings damaged during the war. North American

The fiber cement mixture is formed into siding or

builders began using EIFS in the 1980s, first in

individual boards, then dried and cured using superheated

commercial buildings, then as an exterior finish to wood

steam under pressure. The drying and curing process

frame houses.

assures that the fiber cement siding has very low moisture

content, which makes the product is stable—no warping

EIFS has three layers:

or excessive movement—and its surface good for painting.

• Inner layer—foam insulation board secured to the

Weight is a minor concern with fiber cement products:

exterior wall surface, often with adhesive;

they weigh about 1½ times what comparably sized

composite wood products do. Other concerns relate to

• Middle layer—a polymer and cement base coat

cutting fiber cement: cutting produces a fine dust with

applied to the top of the insulation, then

microscopic silica fibers, so personal protective equipment

reinforced with glass fiber mesh; and

(respirator and goggles) are necessary. In addition, special

tools are needed for cutting.

• Exterior layer—a textured finish coat.

Brick

EIFS layers bond to form a covering that does not

Brick homes may seem on the surface to be nearly

breathe. If moisture seeps in, it can become trapped

maintenance free. This is true in some cases, but, like all

behind the layers. With no place to go, constant exposure

surfaces, brick also degrades. Although this degradation

to moisture can lead to rot in wood and other vulnerable

takes longer in brick than in other materials, repairing

materials within the home. Ripples in the stucco could be

brick is complex and quite expensive. There are two basic

a sign of a problem. On the surface it may look like

types of brick homes. One is brick veneer, which is a thin

nothing is wrong, but beneath the surface, the stucco may

brick set to the outside of a wooden stud wall. The brick

have cracked from settling of the house. With a properly

is not actually the supporting wall. Brick veneer typically

installed moisture barrier, no moisture should be able to

has the same pattern of bricks around the doors and

seep behind the EIFS, including moisture originating

windows; a true brick wall will have brick arches or heavy

inside the home. Drains in the foundation can be

steel plates above the doors and other openings of the

designed to enable moisture that does seep in to escape.

building. Some brick walls have wooden studs behind the

brick to provide an area for insulation, plumbing, vents,

Other signs of problems are mold or mildew on the

and wiring. It is important that weep holes and flashing

interior or exterior of the home, swollen wood around

be installed in brick homes to control moisture.

door and window frames, blistered or peeling paint; and

cracked EIFS or cracked sealant.

Improperly constructed building footers can result in

major damage to the exterior brick surface of a home by

allowing moisture, insects, and vermin to enter. A crack,

7-4

Environmental Barriers

Vinyl

workers and the site must be carefully managed and

Standard vinyl siding is made from thin, flexible sheets of

protected from contamination. The composite had several

plastic about 2 mm thick, precolored and bent into shape

virtues as siding. It was quite resistant to fire, was not

during manufacturing. The sheets interlock as they are

attractive to insects or vermin, provided very good

placed above one another. Because temperature and

insulation, and did not grow mold readily. Because of its

sunlight cause vinyl to expand and contract, it fits into

very brittle nature, it could be damaged by children

deep channels at the corners and around windows and

playing and, as a result, often was covered later with

doors. The channels are deep enough that as the siding

aluminum siding.

contracts, it remains within the channel.

Metal

Siding composed of either vinyl or aluminum will expand

If metal siding is used, the mounting fasteners (nails or

and contract in response to temperature change. This

screws) must be compatible with the metal composition

requires careful attention to the manufacturer’s specifications

of the siding, or the siding or fasteners will corrode. This

during application. Cutting the siding too short causes

corrosion is due to galvanic response.

exposed surfaces when the siding contracts, resulting in

moisture damage and eventual leakage. Even small cracks

Galvanic response (corrosion) can produce devastating

exposing the undersurface can create major damage.

results that often are only noticed when it is too late. It

should always be considered in inspections and is

Vinyl has some environmental and health concerns, as do

preventable in nearly all cases.

most exterior treatments. Vinyl chloride monomer, of which

polyvinyl chloride siding is made, is a strong carcinogen

When two dissimilar metals, such as aluminum and steel,

and, when heated, releases toxic gases and vapors. Under

are coupled and subjected to a corrosive environment

normal conditions, significant exposures to vinyl chloride

(such as air, water, salt spray, or cleaning solutions), the

monomer are unlikely.

more active metal (aluminum) becomes an anode and

corrodes through exfoliation or pitting. This can happen with

Asbestos

plumbing, roofing, siding, gutters, metal venting, and

Older homes were often sided with composites containing

heating and air conditioning systems.

asbestos. This type of siding was very popular in the early

1940s. It was heavily used through the 1950s and

When two metals are electrically connected to each other

decreasingly used up until the early 1960s. The siding is

in a conductive environment, electrons flow from the

typically white, although it may be painted. It is often

more active metal to the less active because of the difference

about ¼-inch thick and very brittle and was sold in

in the electrical potential, the so-called “driving force.”

sections of about 12×18 inches. The composite is quite

When the most active metal (anode) supplies current, it

heavy and very slatelike in difficulty of application. As it

will gradually dissolve into ions in the electrolyte and, at

ages, it becomes even more brittle, and the surface erodes

the same time, produce electrons, which the least active

and becomes powdery. This siding, when removed, must

(cathode) will receive through the metallic connection with

be disposed of in accordance with local, state, and federal

the anode. The result is that the cathode will be negatively

laws regulating the disposal of asbestos materials. The

polarized and hence be protected against corrosion.

Thus, less noble metals are more susceptible to corrosion.

Metal Corrosion Prevention

An example of protecting an appliance such as an iron-

bodied water heater would be to ensure that piping

1. Use like metals when possible

2. Use metals with similar electronegativity

levels

3. Use dielectric unions for plumbing

4. Use anodes that are inexpensive to replace

Remember: Use metals with less susceptibility

to protect metals that are more susceptible

to corrosion.

Figure 7.6. Corrosion in Piping Resulting From Galvanic Response

Healthy Housing Reference Manual

7-5

connections are of similar material when possible and

Stevens Point; no date. Available from URL:

follow the manufacturer’s good practice and instructions on

https://www.uwsp.edu/cnr/etf/corros.htm.

using dielectric (not conductors of electricity) unions [8].

Figure 7.6 shows examples of electrochemical kinetics in

pipes that were connected to dissimilar metals.

References

Lawrence Berkeley National Laboratory. Cool

roofing materials database. Berkeley, CA:

Lawrence Berkeley National Laboratory,

Environmental Energy Technologies Division;

2000. Available from URL:

http://eetd.lbl.gov/coolroof/.

California Energy Commission. Roofing.

Sacramento: California Energy Commission; no

date. Available from URL: http://www.con-

sumerenergycenter.org/homeandwork/homes/

construction/roofing.html.

Cazayoux EJ, Bilello RA. Roof materials. Baton

Rouge, LA: Louisiana State University; no date.

Available from URL: http://www.leeric.lsu.edu/

bgbb/7/ecep/carpntry/i/i.htm.

Department of Energy. Insulation fact sheet.

Washington, DC: Department of Energy; 2002.

Available from URL: http://www.ornl.gov/sci/

roofs+walls/insulation/ins_01.htm.

The Old House Web. Insulation: stories and more

from the Old House Web. Gardiner, ME: The

Old House Web; no date. Available from URL:

http://www.oldhouseweb.com/stories/HowTo/

HVAC_and_Insulation/Insulation/.

The Old House Web. Siding: stories and more

from the Old House Web. Gardiner, ME: The

Old House Web; no date. Available from URL:

http://www.oldhouseweb.com/

stories/How-To/Siding/.

Vandervort D. House siding and architectural

details. Glendale, CA: Hometips.com; no date.

Available from URL: http://www.hometips.com/

home_improvement/siding.html.

University of Wisconsin-Stevens Point. Corrosion,

lead, copper: in-home water supplies—are you at

risk? Stevens Point, WI: University of Wisconsin-

7-6

Environmental Barriers

Chapter 8: Rural Water Supplies and Water-quality Issues

“We never know the worth of water till the well is dry.”

snow) can be collected and contained. The initial quality

of the water depends on the source. Surface water (lakes,

Thomas Fuller

reservoirs, streams, and rivers), the drinking water source

Gnomologia, 1732

for approximately 50% of our population, is generally of

poor quality and requires extensive treatment.

Introduction

Groundwater, the source for the other approximately

One of the primary differences between rural and urban

50% of our population, is of better quality. However, it

housing is that much infrastructure that is often taken

still may be contaminated by agricultural runoff or

for granted by the urban resident does not exist in the

surface and subsurface disposal of liquid waste, including

rural environment. Examples range from fire and police

leachate from solid waste landfills. Other sources, such as

protection to drinking water and sewage disposal. This

spring water and rain water, are of varying levels of quality,

chapter is intended to provide basic knowledge about the

but each can be developed and treated to render it potable.

sources of drinking water typically used for homes in the

rural environment. It is estimated that at least 15% of

Most water systems consist of a water source (such as a

the population of the United States is not served by

well, spring, or lake), some type of tank for storage, and

approved public water systems. Instead, they use individual

a system of pipes for distribution. Means to treat the

wells and very small drinking water systems not covered

water to remove harmful bacteria or chemicals may also be

by the Safe Water Drinking Act (SDWA); these wells and

required. The system can be as simple as a well, a pump,

systems are often untested and contaminated [1]. Many

and a pressure tank to serve a single home. It may be a

of these wells are dug rather than drilled. Such shallow

complex system, with elaborate treatment processes,

sources frequently are contaminated with both chemicals

multiple storage tanks, and a large distribution system

and bacteria. Figure 8.1 shows the change in water

serving thousands of homes. Regardless of system size,

supply source in the United States from 1970 to 1990.

the basic principles to assure the safety and potability of

According to the 2003 American Housing Survey, of the

water are common to all systems. Large-scale water

105,843,000 homes in the United States, water is

supply systems tend to rely on surface water resources,

provided to 92,324,000 (87.2%) by a public or private

and smaller water systems tend to use groundwater.

business; 13,097,000 (12.4%) have a well (11,276,000

drilled, 919,000 dug, and 902,000 not reported) [3].

Groundwater is pumped from wells drilled into aquifers.

Aquifers are geologic formations where water pools, often

Water Sources

deep in the ground. Some aquifers are actually higher

The primary sources of drinking water are groundwater

than the surrounding ground surface, which can result in

and surface water. In addition, precipitation (rain and

flowing springs or artesian wells. Artesian wells are often

Figure 8.1. U.S. Water Supply by Source [2]

Healthy Housing Reference Manual

8-1

drilled; once the aquifer is penetrated, the water flows

• Lowest rate of use—11:30 PM to 5:00 AM,

onto the surface of the ground because of the hydrologic

pressure from the aquifer.

• Sharp rise/high use—5:00 AM to noon (peak

hourly use from 7:00 AM to 8:00 AM),

SDWA defines a public water system as one that provides

piped water to at least 25 persons or 15 service connections

• Moderate use—noon to 5:00 PM (lull around

for at least 60 days per year. Such systems may be owned

3:00 PM), and

by homeowner associations, investor-owned water

companies, local governments, and others. Water not

• Increasing evening use—5:00 PM to 11:00 PM

from a public water supply, and which serves one or only

(second minor peak, 6:00 PM to 8:00 PM).

a few homes, is called a private supply. Private water

supplies are, for the most part, unregulated. Community

Source Location

water systems are public systems that serve people year-

The location of any source of water under consideration

round in their homes. The U.S. Environmental Protection

as a potable supply, whether individual or community,

Agency (EPA) also regulates other kinds of public water

should be carefully evaluated for potential sources of

systems-such as those at schools, factories, campgrounds,

contamination. As a general practice, the maximum

or restaurants-that have their own water supply.

distance that economics, land ownership, geology, and

topography will allow should separate a water source from

potential contamination sources. Table 8.1 details some of

The quantity of water in an aquifer and the water

the sources of contamination and gives minimum

produced by a well depend on the nature of the rock,

distances recommended by EPA to separate pollution

sand, or soil in the aquifer where the well withdraws

sources from the water source.

water. Drinking water wells may be shallow (50 feet or

less) or deep (more than 1,000 feet).

Water withdrawn directly from rivers, lakes, or reservoirs

cannot be assumed to be clean enough for human

On average, our society uses almost 100 gallons of

consumption unless it receives treatment. Water pumped

drinking water per person per day. Traditionally, water use

from underground aquifers will require some level of

rates are described in units of gallons per capita per day

treatment. Believing surface water or soil-filtered water

(gallons used by one person in 1 day). Of the drinking

has purified itself is dangerous and unjustified. Clear

water supplied by public water systems, only a small

water is not necessarily safe water. To assess the level of

portion is actually used for drinking. Residential water

treatment a water source requires, follow these steps:

consumers use most drinking water for other purposes,

such as toilet flushing, bathing, cooking, cleaning, and

• Determine the quality needed for the intended

lawn watering.

purpose (drinking water quality needs to be

evaluated under the SDWA).

The amount of water we use in our homes varies during

the day:

• For wells and springs, test the water for

bacteriologic quality. This should be done with

several samples taken over a period of time to

Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources (Horizontal Distance) [1]

8-2

Rural Water Supplies and Water-quality Issues

Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters

establish a history on the source. With few

However, if the area of well construction has any sources

exceptions, surface water and groundwater sources

of chemical contamination nearby, the local public health

are always presumed to be bacteriologically unsafe

authority should be contacted. In areas with karst

and, as a minimum, must be disinfected.

topography (areas characterized by a limestone landscape

with caves, fissures, and underground streams), wells of

• Analyze for chemical quality, including both legal

any type are a health risk because of the long distances

(primary drinking water) standards and aesthetic

that both chemical and biologic contaminants can travel.

(secondary) standards.

When determining where a water well is to be located,

• Determine the economical and technical restraints

several factors should be considered:

(e.g., cost of equipment, operation and

maintenance costs, cost of alternative sources,

•

the groundwater aquifer to be developed,

availability of power).

•

depth of the water-bearing formations,

• Treat if necessary and feasible.

•

the type of rock formations that will be encountered,

Well Construction

Many smaller communities obtain drinking water solely

•

freedom from flooding, and

from underground aquifers. In addition, according to the

last census with data on water supply systems, 15% of

•

relation to existing or potential sources

people in the United States are on individual water supply

of contamination.

systems. In some sections of the country, there may be a

choice of individual water supply sources that will supply

water throughout the year. Some areas of the country may

be limited to one source. The various sources of water

include drilled wells, driven wells, jetted wells, dug wells,

bored wells, springs, and cisterns. Table 8.2 provides a

more detailed description of some of these wells.

Regardless of the choice for a water supply source, special

safety precautions must be taken to assure the potability

of the water. Drainage should be away from a well. The

casings of the well should be sealed with grout or some other

mastic material to ensure that surface water does not seep

along the well casing to the water source. In Figure 8.2,

the concrete grout has been reinforced with steel and a

drain away from the casing has been provided to assist in

protecting this water source. Additionally, research

suggests that a minimum of 10 feet of soil is essential to

filter unwanted biologic organisms from the water source.

Figure 8.2. Cross Section of a Driven Well

Healthy Housing Reference Manual

8-3

The overriding concern is to protect any kind of well

covers the well opening (Figure 8.3). If pumping at the

from pollution, primarily bacterial contamination.

design rate causes drawdown in the well, a vent through a

Groundwater found in sand, clay, and gravel formations is

tapped opening should be provided. The upper end of the

more likely to be safer than groundwater extracted from

vent pipe should be turned downward and suitably

limestone and other fractured rock formations. Whatever

screened to prevent the entry of insects and foreign matter.

the strata, wells should be protected from

Pump Selection

• surface water entering directly into the top of the well,

A variety of pump types and sizes exist to meet the needs

of individual or community water systems. Some of the

• groundwater entering below ground level without

factors to be considered in selecting a pump for a specific

filtering through at least 10 feet of earth, and

application are well depth, system design pressure,

demand rate in gallons per minute, availability of power,

• surface water entering the space between the well

and economics.

casing and surrounding soil.

Dug and Drilled Wells

Also, a well should be located in such a way that it is

Dug wells (Figures 8.4 and 8.5) were one of the most

accessible for maintenance, inspection, and pump or pipe

common types of wells for individual water supply in the

replacement when necessary. Driven wells (Figure 8.2) are

United States before the 1950s. They were often

typically installed in sand or soil and do not penetrate

constructed with one person digging the hole with a

base rock. They are, as a result, hammered into the ground

shovel and another pulling the dirt from the hole with a

and are quite shallow, resulting in frequent contamination by

rope, pulley, and bucket. Of course, this required a hole

both chemical and bacterial sources.

of rather large circumference, with the size increasing the

potential for leakage from the surface. The dug well also

Sanitary Design and Construction

was traditionally quite shallow, often less than 25 feet,

Whenever a water-bearing formation is penetrated (as in

which often resulted in the water source being

well construction), a direct route of possible water

contamination exists unless satisfactory precautions are

taken. Wells should be provided with casing or pipe to an

adequate depth to prevent caving and to permit sealing of

the earth formation to the casing with watertight cement

grout or bentonite clay, from a point just below the

surface to as deep as necessary to prevent entry of

contaminated water.

Once construction of the well is completed, the top of the

well casing should be covered with a sanitary seal, an

approved well cap, or a pump mounting that completely

Figure 8.3. Well Seal

Figure 8.4. Converted Dug Well [1]

8-4

Rural Water Supplies and Water-quality Issues

contaminated by surface water as it ran through cracks

disinfect the water because of their shallow depth and

and crevices in the ground to the aquifer. Dug wells

possible biologic impurity during changing drainage and

provide potable water only if they are properly located

weather conditions above ground. Figure 8.7 shows a dug

and the water source is free of biologic and chemical

well near the front porch of a house and within 5 feet of a

contamination. The general rule is, the deeper the well,

drainage ditch and 6 feet of a rural road. This well is

the more likely the aquifer is to be free of contaminants,

likely to be contaminated with the pesticide used to

as long as surface water does not leak into the well

termite-proof the home and from whatever runs off the

without sufficient soil filtration.

nearby road and drainage ditch. The well shown is about

15 feet deep. The brick structure around the well holds

Two basic processes are used to remediate dug wells. One

the centrifugal pump and a heater to keep the water from

is to dig around the well to a depth of 10 feet and install

freezing. Although dangerous to drink from, this well is

a solid slab with a hole in it to accommodate a well casing

and an appropriate seal (Figures 8.4 and 8.5). The dirt is

then backfilled over the slab to the surface, and the casing

is equipped with a vent and second seal, similar to a

drilled well, as shown in Figure 8.6. This results in a

considerable reduction in the area of the casing that needs

to be protected. Experience has shown that the disturbed

dirt used for backfilling over the buried slab will continue

to release bacteria into the well for a short time after

modification. Most experts in well modification suggest

installing a chlorination system on all dug wells to

Figure 8.6. Drilled Well [4]

Figure 8.5. Recapped and Sealed Dug Well [1]

Figure 8.7. Typical Dug Well

Healthy Housing Reference Manual

8-5

typical of dug wells used in rural areas of the United

well is so close to the house, the casing is open, and the land

States for drinking water.

slopes toward the well, it is a major candidate for

contamination and not a safe water source.

Samples should not be taken from such wells because they

instill a false sense of security if they are negative for both

Springs

chemicals and biologic organisms. The quality of the

Another source of water for individual water supply is

water in such wells can change in just a few hours

natural springs. A spring is groundwater that reaches the

through infiltration of drainage water. Figure 8.8 shows

surface because of the natural contours of the land.

the septic tank discharge in the drainage ditch 5 feet

upstream of the dug well in Figure 8.7. This potential

Springs are common in rolling hillside and mountain

combination of drinking water and waste disposal presents

areas. Some provide an ample supply of water, but most

an extreme risk to the people serviced by the dug well.

provide water only seasonally. Without proper precautions, the

Sampling is not the answer; the water source should be

water may be biologically or chemically contaminated and

changed under the supervision of qualified environmental

not considered potable.

health professionals.

To obtain satisfactory (potable) water from a spring, it is

Figure 8.9 shows a drilled well. On the left side of the picture

necessary to

is the corner of the porch of the home. The well appears

not to have a sanitary well seal and is likely open to the

• find the source,

air and will accept contaminants into the casing. Because the

• properly develop the spring,

• eliminate surface water outcroppings above the

spring to its source,

• prevent animals from accessing the spring area, and

• provide continuous chlorination.

Figure 8.10 illustrates a properly developed spring. Note

that the line supplying the water is well underground, the

spring box is watertight, and surface water runoff is

diverted away from the area. Also be aware that the water

quality of a spring can change rapidly.

Figure 8.8. Sewage in Drainage Ditch

Cisterns

A cistern is a watertight, traditionally underground

reservoir that is filled with rainwater draining from the

Figure 8.9. Drilled Well

Figure 8.10. Spring Box [5]

8-6

Rural Water Supplies and Water-quality Issues

roof of a building. Cisterns will not provide an ample

The understanding of certain terms (blue box, next page)

supply of water for any extended period of time, unless

is necessary in talking about chlorination.

the amount of water used is severely restricted. Because

the water is coming off the roof, a pipe is generally

Table 8.4 is a chlorination guide for specific water conditions.

installed to allow redirection of the first few minutes of

rainwater until the water flows clear. Disinfection is,

Chlorine is the most commonly used water disinfectant.

nevertheless, of utmost importance. Diverting the first

It is available in liquid, powder, gas, and tablet form.

flow of water does not assure safe, non-polluted water

Chlorine gas is often used for municipal water

because chemicals and biologic waste from birds and other

disinfection, but can be hazardous if mishandled.

animals can migrate from catchment surfaces and from

Recommended liquid, powder, and tablet forms of

windblown sources. In addition, rainwater has a low pH,

chlorine include the following:

which can corrode plumbing pipes and fixtures if not treated.

• Liquid—Chlorine laundry bleach (about 5%

Disinfection of Water Supplies

chlorine). Swimming pool disinfectant or

Water supplies can be disinfected by a variety of methods

concentrated chlorine bleach (12%-17% chlorine).

including chlorination, ozonation, ultraviolet radiation,

heat, and iodination. The advantages and disadvantages of

• Powder—Chlorinated lime (25% chlorine), dairy

each method are noted in Table 8.3.

sanitizer (30% chlorine), and high-test calcium

hypochlorite (65%-75% chlorine).

Table 8.3. Disinfection Methods

Healthy Housing Reference Manual

8-7

Table 8.4. Chlorination Guide for Specific Water Conditions

Definitions of Terms Related to Chlorination

Breakpoint chlorination—A process sometimes used to ensure the presence of free chlorine in public water supplies by

adding enough chlorine to the water to satisfy the chlorine demand and to react with all dissolved ammonia that might

be present. The concentrations of chlorine needed to treat a variety of water conditions are listed in Table 8.4.

Chlorine concentration—The concentration (amount) of chlorine in a volume of water is measured in parts per million

(ppm). In 1 million gallons of water, a chlorine concentration of 1 ppm would require 8.34 pounds of 100% chlorine.

Contact time—The time, after chlorine addition and before use, given for disinfection to occur. For groundwater systems,

contact time is minimal. However, in surface water systems, a contact time of 20 to 30 minutes is common.

Dosage—The total amount of chlorine added to water. Given in parts per million (ppm) or milligrams per liter

(mg/L).

Demand—Chlorine solution used by reacting with particles of organic matter such as slimes or other chemicals and

minerals that may be present. The difference between the amount of chlorine applied to water and total available

chlorine remaining at the end of a specified contact period.

Parts per million—A weight-to-weight comparison; 1 ppm equals 1 pound per million pounds. Because water weighs

8.34 pounds per gallon, it takes 8.34 pounds of any substance per million gallons to equal 1 ppm. In water chemistry,

1 ppm equals 1 mg/L.

Residual—The amount of chlorine left after the demand is met; available (free) chlorine. This portion provides a ready

reserve for bactericidal action. Both combined and free chlorine make up chlorine residual and are involved in disinfection.

Total available chlorine = free chlorine + combined chlorine.

8-8

Rural Water Supplies and Water-quality Issues

• Tablets—High-test calcium hypochlorite

the required chlorine residual. Chlorine residual should be

(65%-75% chlorine).

tested at least once a week to assure effective equipment

operation and solution strengths.

• Gas—Gas chlorine is an economical and

convenient way to use large amounts of chlorine.

A dated record should be kept of solution preparation,

It is stored in steel cylinders ranging in size from

type, proportion of chlorine used, and residual-test results.

100 to 2,000 pounds. The packager fills these

Sensing devices are available that will automatically shut off

cylinders with liquid chlorine to approximately

the pump and activate a warning bell or light when the

85% of their total volume; the remaining 15% is

chlorinator needs servicing.

occupied by chlorine gas. These ratios are required

to prevent tank rupture at high temperatures. It is

Well Water Shock Chlorination

important that direct sunlight never reaches gas

Shock chlorination is used to control iron and sulfate-

cylinders. It is also important that the user of

reducing bacteria and to eliminate fecal coliform bacteria

chlorine knows the maximum withdrawal rate of

in a water system. To be effective, shock chlorination

gas per day per cylinder. For example, the

must disinfect the following: the entire well depth, the

maximum withdrawal rate from a 150-pound

formation around the bottom of the well, the pressure

cylinder is approximately 40 pounds per day at room

system, water treatment equipment, and the distribution

temperature discharging to atmospheric pressure.

system. To accomplish this, a large volume of super-

chlorinated water is siphoned down the well to displace

Chlorine Carrier Solutions

the water in the well and some of the water in the

On small systems or individual wells, a high-chlorine carrier

formation around the well. Check specifications on the

solution is mixed in a tank in the pump house and pumped

water treatment equipment to ensure appropriate protection

by the chlorinator into the system. Table 8.5 shows how

of the equipment.

to make a 200-ppm carrier solution. By using 200 ppm,

only small quantities of this carrier have to be added.

With shock chlorination, the entire system-from the

Depending on the system, other stock solutions may be

water-bearing formation through the well-bore and the

needed to better use existing chemical feed equipment.

distribution system-is exposed to water that has a concentration

of chlorine strong enough to kill iron and sulfate-reducing

bacteria. The shock chlorination process is complex and

tedious. Exact procedures and concentrations of chlorine

for effective shock treatment are available [6,7].

Backflow, Back-siphonage, and Other Water

Quality Problems

In addition to contamination at its source, water can

Table 8.5. Preparing a 200-ppm Chlorine Solution

become contaminated with biologic materials and toxic

construction or unsuitable joint materials as it flows

Routine Water Chlorination (Simple)

through the water distribution system in the home. Water

Most chlorinated public water supplies use routine water

flowing backwards (backflow) in the pipes sucks materials

chlorination. Enough chlorine is added to the water to

back (back-siphonage) into the water distribution system,

meet the chlorine demand, plus enough extra to supply

creating equally hazardous conditions. Other water quality

0.2 to 0.5 ppm of free chlorine when checked after 20 minutes.

problems relate to hardness, dissolved iron and iron bacteria,

acidity, turbidity, color, odor, and taste.

Simple chlorination may not be enough to kill certain

viruses. Chlorine as a disinfectant increases in

Backflow

effectiveness as the chlorine residual is increased and as

Backflow is any unwanted flow of nonpotable water into

the contact time is increased.

a potable water system. The direction of flow is the

reverse of that intended for the system. Backflow may be

Chlorine solutions should be mixed and chlorinators

caused by numerous factors and conditions. For example,

adjusted according to the manufacturer’s instructions.

the reverse pressure gradient may be a result of either a

Chlorine solutions deteriorate gradually when standing.

loss of pressure in the supply main (back-siphonage) or

Fresh solutions must be prepared as necessary to maintain

the flow from a pressurized system through an unprotected

Healthy Housing Reference Manual

8-9

cross-connection (back-pressure). A reverse flow in a

• Color coding in all buildings where there is any

distribution main or in a customer’s system can be created

possibility of connecting two separate systems or

by a change of system pressure wherein the pressure at the

taking water from the wrong source (blue-potable,

supply point becomes lower than the pressure at the point

yellow-nonpotable, and other-chemical and gases).

of use. When this happens, the water at the point of use

will be siphoned back into the system, potentially

An air gap is a physical separation between the incoming

polluting or contaminating it. It is also possible that

water line and maximum level in a container of at least

contaminated or polluted water could continue to

twice the diameter of the incoming water line. If an air

backflow into the public distribution system. The point at

gap cannot be installed, then a vacuum breaker should be

which nonpotable water comes in contact with potable

installed. Vacuum breakers, unlike air gaps, must be

water is called a cross-connection.

installed carefully and maintained regularly. Vacuum

breakers are not completely failsafe.

Examples of backflow causes include supplemental

supplies, such as a standby fire protection tank; fire

Other Water Quality Problems

pumps; chemical feed pumps that overpower the potable

Water not only has to be safe to drink; it should also be

water system pressure; and sprinkler systems.

aesthetically pleasing. Various water conditions affect

water quality. Table 8.6 describes symptoms, causes,

Back-Siphonage

measurements, and how to correct these problems.

Back-siphonage is a siphon action in an undesirable or

reverse direction. When there is a direct or indirect

Protecting the Groundwater Supply

connection between a potable water supply and water of

Follow these tips to help protect the quality of

questionable quality due to poor plumbing design or

groundwater supplies:

installation, there is always a possibility that the public

water supply may become contaminated. Some examples

•

Periodically inspect exposed parts of wells for

of common plumbing defects are

cracked, corroded, or damaged well casings;

broken or missing well caps; and settling and

• washbasins, sterilizers, and sinks with submerged

cracking of surface seals.

inlets or threaded hose bibs and hose;

•

Slope the area around wells to drain surface runoff

• oversized booster pumps that overtax the supply

away from the well.

capability of the main and thus develop negative

pressure;

•

Install a well cap or sanitary seal to prevent

unauthorized use of, or entry into, a well.

• submerged inlets and fire pumps (if the fire

pumps are directly connected into the water main,

•

Disinfect wells at least once a year with bleach or

a negative pressure will develop); and

hypochlorite granules, according to the

manufacturer’s directions.

• a threaded hose bib in a health-care facility (which

is technically a cross-connection).

•

Have wells tested once a year for coliform bacteria,

nitrates, and other constituents of concern.

There are many techniques and devices for preventing

back-flow and back-siphonage. Some examples are

•

Keep accurate records of any well maintenance,

such as disinfection or sediment removal, that

• Vacuum breakers (nonpressure and pressure);

require the use of chemicals in the well.

• Back-flow preventers (reduced pressure principle,

•

Hire a certified well driller for new well construction,

double gate-double check valves, swing-

modification, or abandonment and closure.

connection, and air gap-double diameter

separation);

•

Avoid mixing or using pesticides, fertilizers,

herbicides, degreasers, fuels, and other pollutants

• Surge tanks (booster pumps for tanks, fire system

near wells.

make-up tank, and covering potable tanks); and

•

Do not dispose of waste in dry or abandoned wells.

8-10

Rural Water Supplies and Water-quality Issues

Table 8.6. Analyzing and Correcting Water Quality Problems (continued)

US Census Bureau. Historical census of housing

7. Boulder GNS Water Well Service and Supply.

graphs: water supply. Washington, DC: US

Chlorination of water systems. Boulder, CO:

Census Bureau; no date. Available from URL:

Boulder GNS Water Well Service and Supply;

http://www.census.gov/hhes/www/housing/

2002. Available from URL: http://www.waterwell.cc/

census/historic/swgraph.html.

CHLORIN.HTM.

US Census Bureau. American housing survey.

8. Iowa State University Diagnosing and solving

Washington, DC: US Census Bureau; 2003.

common water-quality problems. Ames, IA: Iowa

Available from URL: http://www.census.gov/hhes/

State University; 1994. Available from URL:

www/housing/ahs/nationaldata.html.

http://www.abe.iastate.edu/HTMDOCS/

aen152.pdf.

National Ground Water Association. Well system

material. Westerville, OH: National Ground

Additional Sources of Information

Water Association; 2003. Available from URL:

American Water Works Association. Available from URL:

http://www.ngwa.org/pdf/wellsystemmaterials.pdf.

http://www.awwa.org.

US Environmental Protection Agency. Spring

Drexel University: Drinking water outbreaks. Available

development. Chicago: US Environmental

from URL: http://water.sesep.drexel.edu/outbreaks/.

Protection Agency; 2001.

US Environmental Protection Agency: Ground water and

Government of Alberta. Shock chlorination—well

drinking water. Available from URL:

maintenance. Edmonton, Alberta, Canada: Alberta

http://www.epa.gov/safewater.

Agriculture, Food & Rural Development;2001.

Available from URL: http://www1.agric.gov.ab.ca/

$department/deptdocs.nsf/all/wwg411.

8-12

Rural Water Supplies and Water-quality Issues

Chapter 9: Plumbing

“The society which scorns excellence in plumbing as a

humble activity and tolerates shoddiness in philosophy

because it is an exalted activity will have neither good

plumbing nor good philosophy: neither its pipes nor its

theories will hold water.”

John W. Gardner, Secretary,

Department of Health, Education, and Welfare, 1965

Introduction

Plumbing may be defined as the practice, materials, and

fixtures used in installing, maintaining, and altering

piping, fixtures, appliances, and appurtenances in

connection with sanitary or storm drainage facilities, a

venting system, and public or private water supply

Figure 9.1. Typical Home Water System [1]

systems. Plumbing does not include drilling water wells;

installing water soften ing equipment; or manufacturing

It is, therefore, very important that the housing inspector

or selling plumbing fixtures, appliances, equipment, or

be completely familiar with all elements of these systems

hardware. A plumbing system consists of three parts: an

so that inade quacies of the structure’s plumbing and

adequate potable water supply system; a safe, adequate

other code violations will be recognized. To aid the

drainage system; and ample fixtures and equipment.

inspector in understanding the plumbing system, a schematic

of a home plumbing system is shown in Figure 9.1.

The housing inspector’s prime concern while inspecting

plumbing is to ensure the provision of a safe water

Water Service

supply system, an adequate drainage system, and ample

The piping of a house service line should be as short as

and proper fixtures and equipment that do not

possible. Elbows and bends should be kept to a minimum

contaminate water. The inspector must make sure that

because they reduce water pressure and, therefore, the

the system moves waste safely from the home and

supply of water to fixtures in the house. The house

protects the occupants from backup of waste and

service line also should be protected from freezing.

dangerous gases. This chapter covers the major features

Four feet of soil is a commonly accepted depth to bury

of a residential plumbing system and the basic plumbing

the line to prevent freezing. This depth varies, however,

terms and principles the inspector must know and

across the country from north to south. The local or state

understand to identify housing code violations that

plumbing code should be consulted for recommended

involve plumbing. It will also assist in identifying the

depths. The minimum service line size should be ¾ inch.

more complicated defects that the inspector should refer

The minimum water supply pressure should be 40 pounds

to the appropriate agencies. This chapter is not a

per square inch (psi), no cement or concrete joints

plumbing code, but should provide a base of knowledge

should be allowed, no glue joints between different types

sufficient to evaluate household systems.

of plastic should be allowed, and no female threaded

PVC fittings should be used.

Elements of a Plumbing System

The primary purposes of a plumbing system are

The materials used for a house service may be approved

plastic, copper, cast iron, steel, or wrought iron. The

• To bring an adequate and potable supply of hot

connections used should be compatible with the type of

and cold water to the inhabitants of a house, and

pipe used. A typical house service installation is pictured

in Figure 9.2. The elements of the service installation are

• To drain all wastewater and sewage discharge

described below.

from fixtures into the public sewer or a private

disposal system.

Corporation stop—The corporation stop is connected to

the water main. This connection is usually made of brass

Healthy Housing Reference Manual

9-1

and can be connected to the main with a special tool

without shutting off the municipal supply. The valve

incorporated in the corporation stop permits the pressure

to be maintained in the main while the service to the

building is completed.

Curb stop—The curb stop is a similar valve used to

isolate the building from the main for repairs,

nonpayment, of water bills or flooded basements. Because

the corporation stop is usually under the street and it is

necessary to break the pavement to reach the valve, the

curb stop is used as the isolation valve.

Curb stop box—The curb stop box is an access box to

Figure 9.2. House Service Installation [1]

the curb stop for opening and closing the valve. A long-

handled wrench is used to reach the valve.

Definitions of Terms Related to Home Water Systems

Air chambers—Pressure-absorbing devices that eliminate water hammer. Air chambers should be installed as close as possible

to the valves or faucet and at the end of long runs of pipe.

Air gap (drainage system)—The unobstructed vertical distance through the free atmosphere between the outlet of a water

pipe and the flood level rim of the receptacle into which it is discharging.

Air gap (water distribution system)—The unobstructed vertical distance through the free atmosphere between the lowest

opening from any pipe or faucet supplying water to a tank, plumbing fixture, or other device and the flood level rim of the

receptacle.

Backflow—The flow of water or other liquids, mixtures, or substances into the distributing pipes of a potable water sup-

ply from any source or sources other than the intended source. Back siphonage is one type of backflow.

Back siphonage—The flowing back of used, contaminated, or polluted water from a plumbing fixture or vessel into a

potable water supply because of negative pressure in the pipe.

Branch—Any part of the piping system other than the main, riser, or stack.

Branch vent—A vent connecting one or more individual vents with a vent stack.

Building drain—Part of the lowest piping of a drainage system that receives the discharge from soil, waste, or other

drainage pipes inside the walls of the building (house) and conveys it to the building sewer beginning 3 feet outside the

building wall.

Cross connection—Any physical connection or arrangement between two otherwise separate piping systems (one of

which contains potable water and the other which contains either water of unknown or questionable safety or steam, gas,

or chemical) whereby there may be a flow from one system to the other, the direction of flow depending on the pressure dif-

ferential between the two systems. (See Backflow and Back siphonage.)

Disposal field—An area containing a series of one or more trenches lined with coarse aggregate and conveying the efflu-

ent from a septic tank through vitrified clay pipe or perforated, nonmetallic pipe, laid in such a manner that the flow will

be distributed with reasonable uniformity into natural soil.

Drain—Any pipe that carries wastewater or waterborne waste in a building (house) drainage system.

Flood level rim—The top edge of a receptacle from which water overflows.

Flushometer valve—A device that discharges a predetermined quantity of water to fixtures for flushing purposes and is

closed by direct water pressures.

Flushometer toilet—a toilet using a flushometer valve that uses pressure from the water supply system rather than the

force of gravity to discharge water into the bowl, designed to use less water than conventional flush toilets.

Flush valve—A device located at the bottom of the tank for flushing toilets and similar fixtures.

9-2

Plumbing

Meter stop—The meter stop is a valve placed on the

outside. The water meter is not shown in Figure 9.2

street side of the water meter to isolate it for installation

because of regional differences in location of the unit.

or maintenance. Many codes require a gate valve on the

house side of the meter to shut off water for plumbing

Because the electric system is sometimes grounded to an

repairs. The curb and meter stops can be ruined in a short

older home’s water line, a grounding loop device should

time if used very frequently.

be installed around the meter. Many meters come with a

yoke that maintains electrical continuity even though the

The water meter is a device used to measure the amount

meter is removed.

of water used in the house. It is usually the property of

the water provider and is a very delicate instrument that

Hot and Cold Water Main Lines

should not be abused. In cold climates, the water meter is

The hot and cold water main lines are usually hung from

often inside the home to keep it from freezing. When the

the basement ceiling or in the crawl space of the home

meter is located inside the home, the company providing

and are attached to the water meter and hot water tank

the water must make appointments to read the meter,

on one side and the fixture supply risers on the other. These

which often results in higher water costs unless the meter

pipes should be installed neatly and should be supported by

is equipped with a signal that can be observed from the

pipe hangers or straps of sufficient strength and number to

Definitions of Terms Related to Home Water Systems

Grease trap—See Interceptor.

Hot water—Potable water heated to at least 120°F-130°F (49°C-54°C) and used for cooking, cleaning, washing dishes,

and bathing.

Insanitary—Unclean enough to endanger health.

Interceptor—A device to separate and retain deleterious, hazardous, or undesirable matter from normal waste and permit

normal sewage or liquid waste to discharge into the drainage system by gravity.

Main vent—The principal artery of the venting system, to which vent branches may be connected.

Leader—An exterior drainage pipe for conveying storm water from roof or gutter drains to the building storm drain,

combined building sewer, or other means of disposal.

Main sewer—See Public sewer.

Pneumatic—Pertaining to devices making use of compressed air as in pressure tanks boosted by pumps.

Potable water—Water having no impurities present in amounts sufficient to cause disease or harmful physiologic effects

and conforming in its bacteriologic and chemical quality to the requirements of the U.S. Environmental Protection

Agency’s Safe Drinking Water Act or meeting the regulations of other agencies having jurisdiction.

P & T (pressure and temperature) relief valve—A safety valve installed on a hot water storage tank to limit temperature

and pressure of the water.

P-trap—A trap with a vertical inlet and a horizontal outlet.

Public sewer—A common sewer directly controlled by public authority.

Relief vent—An auxiliary vent that permits additional circulation of air in or between drainage and systems.

Septic tank—A watertight receptacle that receives the discharge of a building’s sanitary drain system or part thereof and

is designed and constructed to separate solid from liquid, digest organic matter through a period of detention, and allow

the liquids to discharge into the soil outside of the tank through a system of open-joint or perforated piping or through a

seepage pit.

Sewerage system—A system comprising all piping, appurtenances, and treatment facilities used for the collection and

disposal of sewage, except plumbing inside and in connection with buildings served, and the building drain.

Soil pipe—The pipe that directs the sewage of a house to the receiving sewer, building drain or building sewer.

Soil stack—The vertical piping that terminates in a roof vent and carries off the vapors of a plumbing system.

Stack vent—An extension of a solid or waste stack above the highest horizontal drain connected to the stack, sometimes

called a waste vent or a soil vent.

Healthy Housing Reference Manual

9-3

prevent sagging. Older homes that have copper pipe with

In homes without basements, the water lines are

soldered pipes can pose a lead poisoning risk, particularly

preferably located in the crawl space or under the slab.

to children. In 1986, Congress banned lead solder

The water lines are sometimes placed in the attic;

containing greater than 0.2% lead and restricted the lead

however, because of freezing, condensation, or leaks, this

content of faucets, pipes, and other plumbing materials to

placement can result in major water damage to the home.

no more than 8%. The water should be tested to

In two-story or multistory homes, the water line

determine the presence or level of lead in the water. Until

placement for the second floor is typically between the

such tests can be conducted, the water should be run for

studs and, then, for the shortest distance to the fixture,

about 2 minutes in the morning to flush any such

between the joists of the upper floors.

material from the line. Hot and cold water lines should

be approximately 6 inches apart unless the hot water line

Hot and Cold Water Piping Materials

is insulated. This is to ensure that the cold water line does

Care must be taken when choosing the piping materials.

not pick up heat from the hot water line [2].

Some state and local plumbing codes prohibit using some

of the materials listed below in water distribution systems.

The supply mains should have a drain valve stop and waste

valve to remove water from the system for repairs. These

Polyvinyl Chloride (PVC). PVC is a white plastic pipe

valves should be on the low end of the line or on the end of

used outside. It should be used only for cold water. Its

each fixture riser.

uses include water service between the meter and building

and irrigation [3]. PVC, or vinyl, is one of the most

The fixture risers start at the basement main and rise

commonly used materials in the marketplace. It is in

vertically to the fixtures on the upper floors. In a one-

water pipes, packaging, construction and automotive

family dwelling, riser branches will usually proceed from

material, toys, and medical equipment. PVC is also

the main riser to each fixture grouping. In any event, the

known as chloroethene, chloroethylene, and ethylene

fixture risers should not depend on the branch risers for

monochloride. It is a known human carcinogen; PVC

support, but should be supported with a pipe bracket.

causes liver cancer, angiosarcomas, and other health

The size of basement mains and risers depends on the

problems in people who are exposed to it in their work

number of fixtures supplied. However, a ¾-inch pipe is

environment. Significant exposure can occur when the

usually the minimum size used. This allows for deposits

material is heated or in the process of manufacturing the

on the pipe due to hardness in the water and will usually

material. As a result, PVC is closely regulated in the work

give satisfactory volume and pressure.

environment and not commonly recommended for use as

hot water piping.

Definitions of Terms Related to Home Water Systems

Storm sewer—A sewer used for conveying rain water, surface water, condensate, cooling water, or similar liquid waste.

Trap—A fitting or device that provides a liquid seal to prevent the emission of sewer gases without materially affecting

the flow of sewage or wastewater through it.

Vacuum breaker—A device to prevent backflow (back siphonage) by means of an opening through which air may be drawn

to relieve negative pressure (vacuum).

Vapor lock—A bubble of air that restricts the flow of water in a pipe.

Vent stack—The vertical vent pipe installed to provide air circulation to and from the drainage system and that extends

through one or more stories.

Water hammer—The loud thump of water in a pipe when a valve or faucet is suddenly closed.

Water service pipe—The pipe from the water main or other sources of potable water supply to the water-distributing

system of the building served.

Water supply system—Consists of the water service pipe, the water-distributing pipes, the necessary connecting pipes,

fittings, control valves, and all appurtenances in or adjacent to the building or premises.

Wet vent—A vent that receives the discharge of waste other than from water closets.

Yoke vent—A pipe connecting upward from a soil or waste stack to a vent stack to prevent pressure changes in the stacks.

9-4

Plumbing

PVC also contains phthalates, which accumulate in body

saturated water, the pipe will become severely restricted

tissues and can damage the liver and lungs. It has been

by corrosion that eventually fills the pipe completely.

shown in lower mammals to damage reproductive organs.

Another problem is that the mismatch of metals between

Phthalates are freely given off by the plastics in which it is

the brass valves and the steel results in corrosion.

used; and, because it is fat soluble, is found in meats and

Whenever steel pipe meets copper or brass, the steel pipe

cheeses packaged in PVC. Although phthalates show

will rapidly corrode. Dielectric unions can be used

almost no toxicity in adult humans in acute (short-term)

between copper and steel pipes; however, these unions

doses, even at high doses, the cumulative nature of

will close off flow in a short time. The problem with

phthalate toxicity results in toxic effects even at very low

dielectric unions is that they break the grounding effect if

dosages with chronic exposure (over a long period of

a live electrical wire comes in contact with a pipe. Some

time). Very young infants do not metabolize phthalates as

cities require the two pipes to be bonded electrically to

well as do adults, and so are at greater risk for harm. The

maintain the safety of grounded pipes.

availability of phthalates in the consumer environment

causes inevitable chronic ingestion for almost all modern

PEX. PEX is an acronym for a cross-formulated

industrial consumers.

polyethylene. “PE” refers to the raw material used to make

PEX (polyethylene), and “X” refers to the cross-linking of

Lead is used as a hardening agent to manufacture PVC

the polyethylene across its molecular chains. The

materials. Therefore, it is very important that third-party

molecular chains are linked into a three-dimensional

testing be done on PVC piping. PVC piping should have

network that makes PEX remarkably durable within a wide

the stamp of both the testing laboratory and a potable

range of temperatures, pressures, and chemicals [6].

water (PW) mark to indicate that it meets appropriate

standards for use as potable water piping.

PEX is flexible and can be installed with fewer fittings

than rigid plumbing systems. It is a good choice for

Chlorinated PVC (CPVC). CPVC is a slightly yellow

repiping and for new homes and works well for corrosive

plastic pipe used inside homes. It has a long service life,

water conditions. PEX stretches to accommodate the

but is not quite as tough as copper. Some areas with

expansion of freezing water and then returns to its

corrosive water will benefit by using chlorinated PVC

original size when water thaws. Although it is highly

piping. CPVC piping is designed and recommended for

freeze-resistant, no material is freeze-proof.

use in hot and cold potable water distribution systems [4].

Kitec. Kitec is a multipurpose pressure pipe that uniquely

Copper. Copper comes in three grades:

unites the advantages of both metal and plastic. It is made

of an aluminum tube laminated to interior and exterior

• Mfor thin wall pipe (used mainly inside homes);

layers of plastic. Kitec provides a composite piping system

for a wide range of applications, often beyond the scope of

• L for thicker wall pipe (used mainly outside for

metal or plastic alone. Unlike copper and steel materials,

water services); and

Kitec is noncorroding and resists most acids, salt

solutions, alkalis, fats, and oils.

• K, the thickest (used mainly between water mains

and the water meter).

Poly. Poly pipe is a soft plastic pipe that comes in coils

and is used for cold water. It can crack with age or wear

Copper lasts a long time, is durable, and connects well to

through from rocks. Other weak points can be the

valves. It should not be installed if the water has a pH of

stainless steel clamps or galvanized couplings.

6.5 or less. Most public utilities supply water at a pH

between 7.2 and 8.0. Many utilities that have source

Polybutylene [Discontinued]. Polybutylene pipe is a soft

water with a pH below 6.5 treat the water to raise the

plastic pipe. This material is no longer recommended

pH. Private well water systems often have a pH below

because of early chemical breakdown. Individuals with a

6.5. When this is the case, installing a treatment system

house, mobile home, or other structure that has

to make the water less acidic is a good idea [5].

polybutylene piping with acetal plastic fittings may be

eligible for financial relief if they have replaced that

Galvanized Steel. Galvanized pipe corrodes rather easily.

plumbing system. For claims information, call 1-800-

The typical life of this piping is about 40 years. One of

392-7591 or go to www.pbpipe.com.

the primary problems with galvanized steel is that, in

Healthy Housing Reference Manual

9-5

Hot Water Safety

valves are common shutoff valves. Gate and ball valves

In the United States, more than 112,000 people enter a

cause less friction loss than do globe valves; ball valves last

hospital emergency room each year with scald burns. Of

longer and leak less than do gate valves. Shutoff valves

these, 6,700 (6%), have to be hospitalized. Almost 3,000 of

allow servicing of parts of the system without draining the

these scald burns come from tap water in the home. The

entire system.

three high risk groups are children under the age of 5 years,

the handicapped, and adults over the age of 65 years. It

Flow-control Valves. Flow-control valves provide uniform

only takes 1 second to get a serious third-degree burn

flow at varying pressures. They are sometimes needed to

from water that is 156°F (69°C). Tap water is too hot if

regulate or limit the use of water because of limited water

instant coffee granules melt in it.

flow from low-yielding wells or an inadequate pumping

system. They also may be needed with some treatment

Young children, some handicapped individuals, and

equipment. These valves are often used to limit flow to a

elderly people are particularly vulnerable to tap water

fixture. Orifices, mechanical valves, or diaphragm valves

burns. Children cannot always tell the hot water faucets

are used to restrict the flow to any one service line or

from the cold water faucets. Children have delicate skin

complete system and to assure a minimum flow rate to all

and often cannot get out of hot water quickly, so they

outlets.

suffer hot water burns most frequently. Elderly and

handicapped persons are less agile and more prone to falls

Relief Valves. Relief valves permit water or air to escape

in the bath tub. They also may have diseases, such as

from the system to relieve excess pressure. They are

diabetes, that make them unable to feel heat in some

spring-controlled and are usually adjustable to relieve

regions of the body, such as the hands and feet. Third-

varying pressures, generally above 60 psi. Relief valves

degree burns can occur quickly—in 1 second at 156°F

should be installed in systems that may develop pressures

(69°C), in 2 seconds at 149°F (65°C), in 5 seconds at

exceeding the rated limits of the pressure tank or

140°F (60°C), and in 15 seconds at 133°F (56°C).

distribution system. Positive displacement and

submersible pumps and water heaters can develop these

A tap-water temperature of 120°F-130°F (49°C-54°C) is

excessive pressures. The relief valve should be installed

hot enough for washing clothes, bedding, and dishes.

between the pump and the first shutoff valve and must be

Even at 130°F (54°C), water takes only a few minutes of

capable of discharging the flow rate of the pump. A

constant contact to produce a third-degree burn. Few

combined pressure and temperature relief valve is needed

people bathe at temperatures above 110°F (43°C), nor

on all water heaters. Combination pressure and vacuum

should they. Water heater thermostats should be set at

relief valves also should be installed to prevent vacuum

about 120°F (49°C) for safety and to save 18% of the

damage to the system.

energy used at 140°F (60°C). Antiscald devices for faucets

and showerheads to regulate water temperature can help

Pressure-reducing Valves. A pressure-reducing valve is

prevent burns. A plumber should install and calibrate

used to reduce line pressure. On main lines, this allows

these devices. Most hot water tank installations now

the use of thinner walled pipe and protects house

require an expans ion tank to reduce pressure fluctuations

plumbing. Sometimes these valves are installed on

and a heat trap to keep hot water from escaping up pipes.

individual services to protect plumbing.

Types of Water Flow Controls

Altitude Valves. Often an altitude valve is installed at the

It is essential that valves be used in a water system to

base of a hot water tank to prevent it from overflowing.

allow the system to be controlled in a safe and efficient

Altitude valves sense the tank level through a pressure line

manner. The number, type, and size of valves required

to the tank. An adjustable spring allows setting the level

will depend on the size and complexity of the system. Most

so that the valve closes and prevents more inflow when

valves can be purchased in sizes and types to match the

the tank becomes full.

pipe sizes used in water system installations. Listed below

are some of the more commonly encountered valves with

Foot Valves. A foot valve is a special type of check valve

a description of their basic functions.

installed at the end of a suction pipe or below the jet in a

well to prevent backflow and loss of prime. The valve

Shutoff Valves. Shutoff valves should be installed between

should be of good quality and cause little friction loss.

the pump and the pressure tank and between the pressure

tank and service entry to a building. Globe, gate, and ball

9-6

Plumbing

Check Valves. Check valves have a function similar to

into open potable water containers. If identified, these

foot valves. They permit water flow in only one direction

conditions should be corrected immediately to prevent

through a pipe. A submersible pump may use several

the spread of disease or poisoning from high concentrations

check valves. One is located at the top of the pump to

of organic or inorganic chemicals in the water.

prevent backflow from causing back spin of the impellers.

Some systems use another check valve and a snifter valve.

Water Heaters

They will be in the drop pipe or pitless unit in the well

Water heaters (Figure 9.3) are usually powered by

casing and allow a weep hole located between the two

electricity, fuel oil, gas, or, in rare cases, coal or wood.

valves to drain part of the pipe. When the pump is started,

They consist of a space for heating the water and a

it will force the air from the drained part of the pipe into

storage tank for providing hot water over a limited period

the pressure tank, thus recharging the pressure tank.

of time. All water heaters should be fitted with a

temperature-pressure (T&P) relief valve no matter what

Frost-proof Faucets. Frost-proof faucets are installed

fuel is used. The installation port for these valves may be

outside a house with the shutoff valve extending into the

found on the top or on the side of the tank near the top.

heated house to prevent freezing. After each use, the water

T&P valves should not be placed close to a wall or door

between the valve and outlet drains, provided the hose is

jamb, where they would be inaccessible for inspection and

disconnected, so water is not left to freeze.

use. Hot water tanks sometimes are sold without the

T&P valve, and it must be purchased separately. This fact

Frost-proof Hydrants. Frost-proof hydrants make outdoor

alone should encourage individual permitting and

water service possible during cold weather without the

inspection by counties and municipalities to ensure that

danger of freezing. The shutoff valve is buried below the

they are installed. The T&P valve should be inspected at a

frost line. To avoid submerging it, which might result in

minimum of once per year.

contamination and back siphoning, the stop-and-waste

valve must drain freely into a rock bed. These hydrants

A properly installed T&P valve will operate when either

are sometimes prohibited by local or state health authorities.

the temperature or the pressure becomes too high due to

an interruption of the water supply or a faulty thermostat.

Float Valves. Float valves respond to a high water level to

Figure 9.3 shows the correct installation of a gas water

close an inlet pipe, as in a tank-type toilet.

Miscellaneous Switches. Float switches respond to a high

and/or low water level as with an intermediate storage

tank. Pressure switches with a low-pressure cutoff stop the

pump motor if the line pressure drops to the cutoff point.

Low-flow cutoff switches are used with submersible

pumps to stop the pump if the water discharge falls below

a predetermined minimum operating pressure. High-

pressure cut-off switches are used to stop pumps if the

system pressure rises above a predetermined maximum.

Paddle-type flow switches detect flow by means of a

paddle placed in the pipe that operates a mechanical

switch when flow in the pipe pushes the paddle.

The inadvertent contamination of a public water supply

as a result of incorrectly installing plumbing fixtures is a

poten tial public health problem in all communities.

Continuous surveillance by environmental health

personnel is necessary to know whether such public

health hazards have developed as a result of additions or

alterations to an approved system. All environmental

health specialists should learn to recognize the three

general types of defects found in potable water supply

Figure 9.3. Gas Water Heater [1]

systems: backflow, back siphonage, and overhead leakage

Healthy Housing Reference Manual

9-7

heater. Particular care should be paid to the exhaust port

The appeal of demand water heaters is not only the

of the T&P valve. Figure 9.4 shows the placement of the

elimination of the tank standby losses and the resulting

T&P valve. This vent should be directed to within

lower operating costs, but also the fact that the heater

6 inches of the floor, and care must be taken to avoid

delivers hot water continuously. Most tankless models

reducing the diameter of the vent and creating any

have a life expectancy of more than 20 years. In contrast,

unnecessary bends in the discharge pipe. Most codes will

storage tank water heaters last 10 to 15 years. Most

allow only one 90° bend in the vent. The point is to

tankless models have easily replaceable parts that can

avoid any constrictions that could slow down the steam

extend their life by many years more.

release from the tank to avoid explosive pressure buildup.

Drainage System

Water heaters that are installed on wooden floors should

Water is brought into a house, used, and discharged

have water collection pans with a drainage tube that drains to

through the drainage system. This system is a sanitary

a proper drain. The pan should be checked on a regular basis.

drainage system carrying just interior wastewater.

Tankless Water Heaters

Sanitary Drainage System

A tankless unit has a heating device that is activated by

The proper sizing of the sanitary drain or house drain

the flow of water when a hot water valve is opened. Once

depends on the number of fixtures it serves. The usual

activated, the heater delivers a constant supply of hot

minimum size is 4 inches in diameter. The materials used

water. The output of the heater, however, limits the rate

are usually cast iron, vitrified clay, plastic, and, in rare

of the heated water flow. Demand water heaters are

cases, lead. The top two pipe choices for drain, waste, and

available in propane (LP), natural gas, or electric models.

vent (DWV) systems are PVC or ABS. For proper flow in

They come in a variety of sizes for different applications,

the drain, the pipe should be sized and angled so that the

such as a whole-house water heater, a hot water source for

pipe is approximately half full. This ensures proper

a remote bathroom or hot tub, or as a boiler to provide

scouring action so that the solids contained in the waste

hot water for a home heating system. They can also be

will not be deposited in the pipe.

used as a booster for dishwashers, washing machines, and a

solar or wood-fired domestic hot water system [7].

Using PVC in DWV pipe is a two-step process needing a

primer and then cement. ABS uses cement only. In most

cases the decision will be made on the basis of which

material is sold in an area. Few areas stock both materials

because local contractors usually favor one or the other.

ABS costs more than PVC in many areas, but Schedule

40 PVC DWV solid core pipe is stronger than ABS.

Their durability is similar.

Size of House Drain. The Uniform Plumbing Code

Committee has developed a method of sizing house

drains in terms of fixture units. One fixture unit equals

approximately 7½ gallons of water per minute. This is the

surge flow rate of water discharged from a wash basin in

one minute.

All other fixtures have been related to this unit. Fixture

unit values are shown in Table 9.1.

Grade of House Drain. A house drain should be sloped

toward the sewer to ensure scouring of the drain. The

usual pitch of a house or building sewer is a ¼-inch drop

in 1 foot of length. The size of the drain is based on the

fixture units flowing into the pipe and the slope of the

drain. Table 9.2 shows the required pipe size for the system.

Figure 9.4. Temperature-Pressure Valve

9-8

Plumbing

House Drain Installation. Typical branch connections to

originates in many different sections of the system,

the main are shown in Figure 9.5.

pressures vary widely in the waste lines. These pressure

differences tend to remove the water seal in the trap. The

Fixture and Branch Drains. A branch drain is a waste

waste system must be properly vented to prevent the traps

pipe that collects the waste from two or more fixtures and

from siphoning dry, thus losing their water seal and

conveys it to the sewer. It is sized in the same way as the

allowing gas from the sewer into the building.

sewer, taking into account that all toilets must have a

minimum 3-inch diameter drain, and only two toilets

Objectionable Traps. The S-trap and the ¾ S-trap

may connect into one 3-inch drain. All branch drains

(Figure 9.7) should not be used in plumbing installations.

must join the house drain with a Y-fitting as shown in

They are almost impossible to ventilate properly, and the

Figure 9.5. The same is true for fixture drains joining

¾ S-trap forms a perfect siphon. Mechanical traps were

branch drains. The Y-fitting is used to eliminate, as much

introduced to counteract this problem. It has been found,

as possible, the deposit of solids in or near the

however, that the corrosive liquids flowing in the system

connection. A buildup of these solids will block the drain.

corrode or jam these mechanical traps. For this reason, most

Recommended minimum sizes of fixture drains are shown

plumbing codes prohibit mechanical traps.

in Table 9.2.

Traps

A plumbing trap is a device used in a waste system to

prevent the passage of sewer gas into the structure and yet

not hinder the fixture’s discharge to any great extent. All

fixtures connected to a household plumbing system

should have a trap installed in the line. The effects of

sewer gases on the human body are well known; many of

the gases are extremely harmful. In addition, certain sewer

gases are explosive.

P-trap. The most commonly used trap is the P-trap

(Figure 9.6). The depth of the seal in a trap is usually

2 inches. A deep seal trap has a 4-inch seal.

As mentioned earlier, the purpose of a trap is to seal out

sewer gases from the structure. Because a plumbing

system is subject to wide variations in flow, and this flow

Table 9.1. Fixture Unit Values

Table 9.2. Sanitary House Drain Sizes

Healthy Housing Reference Manual

9-9

Figure 9.5. Branch Connections

Figure 9.6. P-trap [1]

The bag trap, an extreme form of S-trap, is seldom found.

fixture is emptied and clears

the trap. This is caused by the

Figure 9.7 also shows this type of S-trap.

pressure of air on the water of

the fixture being greater than

Traps are used only to prevent the escape of sewer gas into

the pressure of air in the waste

the structure. They do not compensate for pressure

pipe. The action of the water

variations. Only proper venting will eliminate pressure

discharging into the waste pipe

problems.

removes the air from that pipe

and thereby causes a negative

Ventilation

pressure in the waste line.

A plumbing system is ventilated to prevent trap seal loss,

material deterioration, and flow retardation.

In the case of indirect or

momentum siphonage, the

Trap Seal Loss. The seal in a plumbing trap may be lost

flow of water past the entrance

due to siphonage (direct and indirect or momentum),

to a fixture drain in the waste

back pressure, evaporation, capillary attraction, or wind

pipe removes air from the

fixture drain. This reduces the

effect. The first two are probably the most common

air pressure in the fixture

causes of loss. Figure 9.8 depicts this siphonage process;

drain, and the entire assembly

Figure 9.9 depicts loss of trap seal.

acts as an aspirator. (Figures

9.10 and 9.11 show plumbing

If a waste pipe is placed vertically after the fixture trap, as

configurations that would

in an S-trap, the wastewater continues to flow after the

allow this type of siphonage to

occur.)

Back Pressure. The flow of

water in a soil pipe varies

according to the fixtures being

used. Small flows tend to cling

to the sides of the pipe, but

large ones form a slug of waste

Figure 9.8. Trap Seal: [a]

as they drop. As this slug of

Seal Intact; [b] Fixture

water falls down the pipe, the

Draining; [c] Loss of Gas

Seal [1]

air in front of it becomes

Figure 9.7. Types of S-traps

9-10

Plumbing

pressurized. As the pressure

builds, it seeks an escape

point. This point is either a

vent or a fixture outlet. If the

vent is plugged or there is no

vent, the only escape for this

air is the fixture outlet.

The air pressure forces the

trap seal up the pipe into the

fixture. If the pressure is great

enough, the seal is blown out

of the fixture entirely. Figures

9.8 and 9.9 illustrate the

potential for this type of

problem. Large water flow past

the vent can aspirate the water

from the trap, while water

Figure 9.9. Loss of Trap Seal in

flow approaching the trap can

Lavatory Sink [1]

blow the water out of the trap.

Vent Sizing. Vent pipe installation is similar to that of soil

and waste pipe. The same fixture unit criteria are used.

Table 9.3 shows minimum vent pipe sizes.

Vent pipes of less than 1¼ inches in diameter should not

be used. Vents smaller than this diameter tend to clog and

Figure 9.10. Back-to-back Venting [Toilet]

do not perform their function.

Individual Fixture Ventilation. Figure 9.12 shows a

typical installation of a wall-hung plumbing unit. This

type of ventilation is generally used for sinks, drinking

fountains, and so forth. Air admittance valves are often

used for individual fixtures. Figure 9.13 shows a typical

installation of a bathtub or shower ventilation system.

Figure 9.14 shows the proper vent connection for toilet

fixtures and Figure 9.15 shows a janitor’s sink or slop sink

that has the proper P-trap. For the plumbing fixture to

work properly, it must be vented as in Figures 9.13 and 9.14.

Unit Venting. Figures 9.10 and 9.11 show a back-to-back

shared ventilation system for various plumbing fixtures.

The unit venting system is commonly used in apartment

Figure 9.11. Back-to-back Venting [Sink]

buildings. This type of system saves a great deal of money

and space when fixtures are placed back-to-back in

separate apartments. It does, however, pose a problem if

Total Drainage System

the vents are undersized because they will aspirate the

The drain, soil waste, and vent systems are all connected, and

water from the other trap. Figure 9.16 shows a double

the inspector should remember the following fundamentals:

combination Y-trap used for joining the fixtures to the

Working vents must provide air to all fixtures to ensure

common soil pipe fixture on the other side of the wall.

the movement of waste into the sewer. Improperly vented

fixtures will drain slowly and clog often. They also present

Wet Venting. Bathroom fixture groupings are commonly

a health risk if highly toxic and explosive sewer gases enter

wet vented; that is, the vent pipe also is used as a waste line.

the home. Correct venting is shown in Figures 9.10-9.15;

incorrect venting is shown in Figures 9.8 and 9.9. A wet

Healthy Housing Reference Manual

9-11

Table 9.3. Minimum Fixture Service Pipe Diameters

vent can result in one of the traps siphoning the other dry

when large volumes of water are poured down the drain.

Wet vents are not permitted by many state plumbing

codes because of the potential for self-siphoning.

Backup of sewage into sinks, dishwashers, and other

appliances is always a possibility unless the system is

equipped with air gaps or vacuum breakers. All

connections to the potable water system must be a

minimum of two pipe diameters above the overflow of

the appliance and, in some cases, where flat surfaces are

near, two and one-half pipe diameters above the overflow

of the appliance.

A simple demonstration of how easily siphoning can

occur is to hold a glass of water with food coloring in it

with the tip of a faucet in the colored water. If the sink’s

vegetable sprayer is directed to a second glass and sprayed,

in most cases, the colored water will be aspirated into the

faucet and then out of the sprayer into the second glass.

Weed or pest killer attachments that hook to garden hoses

Figure 9.12. Wall-hung Fixtures

work on the same principle. Figure 9.17 shows an outside

hose bib equipped with a vacuum breaker. In the areas of

the United States that freeze, these vacuum breakers must

be removed because they trap water in the area of the line

that can freeze and burst. Many vacuum breakers sold

today automatically drain to prevent freeze damage.

Figure 9.13. Unit Vent Used in Bathtub Installation

Figure 9.14. Toilet Venting

9-12

Plumbing

The

susceptibility of

metal to

corrosion is as

follows (most

susceptible to

least susceptible):

magnesium, zinc,

aluminum,

cadmium, mild

Figure 9.17. Hose Bib With Vacuum Breaker

steel, cast iron,

stainless steel (active), lead-tin solder, lead, tin, brass, gun

metal, aluminum bronze, copper, copper-nickel alloy,

Monel, titanium, stainless steel (passive), silver, gold, and

platinum.

Figure 9.15. Janitor’s Sink

Water Conservation

How much attention should be paid to fixtures that just

Devices that pull water from a utility may create negative

drip a little bit of water or that just will not quite shut

pressures that can damage water piping and pull

off? At 30 drops per minute, you will lose and pay for

dangerous substances into the line at the same time.

54 gallons per month. At 60 drops per minute, you will

These devices include power sprayers that hook to the

lose and pay for 113 gallons per month. At 120 drops per

home hose bib (outside faucets) and pressurize the spray

minute, you will lose and pay for 237 gallons per month.

by creating a vacuum on the supply side.

This is only a small loss of water considering the 5 to

Corrosion Control

7 gallons per flush used by a properly functioning toilet.

To understand the proper maintenance procedures for the

If the toilet is not properly maintained, the loss of water

prevention and elimination of water quality problems in

and its effect on the monthly water bill can be incredible.

plumbing systems, it is necessary to understand the

Lower flow toilets have been mandated to save precious

process used to determine the chemical aggressiveness of

and limited resources. Most pre-1992 toilets used up to

water. The process is used to determine when additional

7 gallons per flush. Toilets have since evolved to use 5.5,

treatment is needed. Water that is out of balance can

then 3.5, and now 1.6 gallons per flush.

result in many negative outcomes, from toxic water to

damaged and ruined equipment.

With the changes in the water usage laws in 1992, there

were many customer complaints, and plumbers were in the

Water dissolves and carries materials when it is not

bad position of installing products that nobody wanted to

saturated. An equilibrium among pH, temperature,

use. New and updated products now work better than the

alkalinity, and hardness controls water’s ability to create

old water wasters.

scale or to dissolve material. If water is saturated with

harmless or beneficial substances, such as calcium, then

According to the EPA, in 2000, a typical U.S. family of

the threat of damage can be mitigated. The Langelier

four spent approximately $820 every year on water and sewer

method, developed in the early 1930s, is a process used in

fees, plus another $230 in energy for heating water. In

boiler management,

many cities, according to the U.S. EPA, water and sewer

municipal water

costs can be more than twice those amounts. Many people do

treatment, and

not realize how much money they can save by taking simple

swimming pools to

steps to save water, and they do not know the cumulative

provide this balance. In

effects small changes can have on water resources and

the Langelier index,

environmental quality. Fixing a leaky faucet, toilet, or

saturation over 0.3 is

lawn-watering system can reduce water consumption.

scale forming, and a

Changing to water-efficient plumbing fixtures and

saturation below 0.3 is

appliances can result in major water and energy savings [9,10].

Figure 9.16. Common Y-trap

corrosive.

Healthy Housing Reference Manual

9-13

Summer droughts remind many of the need to appreciate

has a rain shutoff device and that it is

clean water as an invaluable resource. As the U.S. population

appropriately scheduled. Drip irrigation should be

increases, the need for clean water supplies continues to

considered where practical. Newer irrigation

grow dramatically and puts additional stress on our limited

systems have sensors to prevent watering while it

water resources. We can all take steps to save and conserve

is raining.

this valuable resource.

Putting It All Together

The EPA [11] suggests the following steps homeowners

These photographs, taken during construction of a home

should take right away to save water and money:

by Habitat for Humanity, show various plumbing

elements discussed in this chapter.

•

Stop leaks!—Check indoor water-using

appliances and devices for leaks. Pay particular

attention to toilets that leak.

•

Take showers—Showers use considerably less

water than do baths.

•

Replace shower heads—Replacement shower

heads are available that reduce water use.

•

Turn the water off when not needed—While

brushing your teeth, turn the water off until you

need to rinse.

•

Replace your old toilet—The largest water user

inside the home is the toilet. If a home was built

before 1992 and the toilet has never been

replaced, it is very likely that it is not a water-

Hot and cold copper water lines and drain, p-trap and vent,

efficient, 1.6 gallons-per-flush toilet. Choose a

and vent for the washer drain shown. When a house is

replacement toilet carefully to ensure that what

vacant for awhile, the P-trap should be filled with water to

you make up per individual flush, you do not lose

prevent sewer gas from entering the home. Mineral oil added

because you must flush more often.

to the water can slow the loss of fluid in the trap.

•

Replace your clothes washer—The second largest

water user in the home is the washing machine.

Energy Star-rated washers that also have a water

factor at or lower than 9.5 use 35%-50% less

water and 50% less energy per load. This saves

money on both water and energy bills.

•

Plant the right plants with proper landscape

design and irrigation—Select plants that are

appropriate for the local climate. Having a 100%

turf lawn in a dry desert climate uses a significant

amount of water. Also, home owners should consider

the benefits of a more natural landscape or wildscape.

•

Water plants only as needed—Most water wasted

in the garden is by watering when plants do not

need it or by not maintaining the irrigation system.

If manually watering, set a timer and move the

Hot and cold water pipes, soil pipe, and vent shown.

hose promptly. Make sure the irrigation controller

9-14

Plumbing

Vent for the sink and toilet, soil pipe, and cap for toilet

Mixing and antiscald water flow contro, vent for fixture, hot

connection shown. A wax or plastic seal shaped like a donut

and cold water lines, and bathtub overflow shown. At this

will be placed on the cap before bolting down the toilet.

point in construction, insulation might be considered for the

hot water lines. Water service and waste water line.

installations. Washington, DC: Occupational

Safety and Health Administration; 1988.

Polyethylene water

http://www.osha.gov/dts/hib/hib_data/

service pipe entering

hib19880520.html.

the home through the

concrete basement wall

Copper Development Association. Copper in

shown. White plastic

adapter shown

your home: plumbing, heating, cooling. New

between polyethylene

York: Copper Development Association; no date.

water service pipe and

Available from URL: http://www.copper.org/

¾ inch copper water

copperhome/PHC/phc_home.html.

line. A short distance

above the adapter is a

Plastic Pipe and Fittings Association. Cross-linked

pressure reducing

valve. To the right of

polyethylene. Glen Ellyn, IL: Plastic Pipe and

water line is the 4-inch PVC pipe waste water line.

Fittings Association; no date. Available from

URL:

http://www.ppfahome.org/pex/historypex.html.

References

NAMCO. Determine the total fixture unit load.

1. US Environmental Protection Agency. United

Dallas: NAMCO; no date. Available from URL:

States Environmental Protection Agency guidance

http://www.namco-div.com/booster/

from hotline compendium: lead ban.

sel%20criteria/fixtureload.htm.

Washington, DC: US Environmental Protection

Agency; 1988. Available from URL:

Energy Efficiency and Renewable Energy

http://www.epa.gov/safewater/wsg/wsg_H19.pdf.

Clearinghouse. Demand (tankless or

instantaneous) water heaters. Merrifield, VA:

2. Uni-Bell PVC Pipe Association. Handbook of

Energy Efficiency and Renewable Energy

PVC pipe design and construction. Dallas: Uni-

Clearinghouse; no date. Available from URL:

Bell PVC Pipe Association; 2001. Available from

http://www.toolbase.org/tertiaryT.asp?

URL: http://www.uni-bell.org/pubs/

DocumentID=3206&&&CategoryID=0.

handbook.pdf.

Public Health-Seattle and King County. Public

3. Occupational Safety and Health Administration.

health plumbing program: water supply fixture

Safety hazard information bulletin on the use of

units (WSFU) and minimum fixture branch pipe

polyvinyl chloride (PVC) pipe in above ground

sizes. Seattle, WA: Public Health-Seattle and King

Healthy Housing Reference Manual

9-15

County; no date. Available from URL: http://

www.metrokc.gov/health/plumbing/wsfu.htm.

US Environmental Protection Agency. Developing

water system financial capacity. Washington, DC:

US Environmental Protection Agency; 2002.

Available from URL:

http://www.epa.gov/safewater/dwa/

electronic/presentations/pwsoper/fincapacity.pdf.

10. US Environmental Protection Agency. Water and

wastewater pricing. Washington, DC: US

Environmental Protection Agency; no date.

Available from URL: http://www.epa.gov/water/

infrastructure/pricing/.

11. US Environmental Protection Agency. Using

water wisely in the home. Washington, DC: US

Environmental Protection Agency; 2002.

Available from URL:

http://www.epa.gov/owm/water-efficiency/

waterconservation_final.pdf.

Additional Sources of Information

American Backflow Prevention Association. Available

from URL: http://www.abpa.org.

American Society of Plumbing Engineers. Available from

URL: http://aspe.org.

American Society of Sanitary Engineering. Available from

URL: http://www.asse-plumbing.org.

American Water Works Association. Available from URL:

http://www.awwa.org.

National Sanitation Foundation. Available from URL:

http://www. nsf.org/international.

Plumbing-Heating-Cooling Contractors Association.

Available from URL: http://www.phccweb.org.

Underwriters Laboratories Inc. Available from URL:

http://www.ul.com.

For more water conservation tips and energy saving ideas

for businesses, industries, and individuals, visit the EPA’s

Water-use Efficiency Program Web site

(http://www.epa.gov/owm/water-effic iency/index.htm).

9-16

Plumbing

Chapter 10: On-site Wastewater Treatment

“Technology has made large populations possible;

These private disposal systems are typically called septic

large populations now make technology indispensable.”

tank systems. A septic tank is a sewage holding device

made of concrete, steel, fiberglass, polyethylene, or other

Joseph Wood Krutch, Author, 1932

approved material cistern, buried in a yard, which may

hold 1,000 gallons or more of wastewater. Wastewater

Introduction

flows from the home into the tank at one end and leaves

The French are considered the first to use an

the tank at the other (Figure 10.1) [2].

underground septic tank system in the 1870s. By the

mid 1880s, two-chamber, automatic siphoning septic

Proper maintenance of septic tanks is a public health

tank systems, similar to those used today, were being

necessity. Enteric diseases such as cryptospordiosis,

installed in the United States. Even now, more than a

giardiasis, salmonellosis, hepatitis A, and shigellosis may

century later, septic tank systems represent a major

be transmitted through human excrement. Historically,

household wastewater treatment option. Fully one-fourth

major epidemics of cholera and typhoid fever were

to one-third of the homes in the United States use such a

primarily caused by improper disposal of wastewater. The

system [1].

earliest epidemiology lesson learned was through the

effort of Dr. John Snow of England (1813-1858) during

On-site sewage disposal systems are used in rural areas

a devastating cholera epidemic in London [3]. Dr. Snow,

where houses are spaced so far apart that a sewer system

known as the father of field epidemiology, discovered

would be too expensive to install, or in areas around

that the city's water supply was being contaminated by

cities where the city government has not yet provided

improper disposal of human waste. He published a brief

sewers to which the homes can connect. In these areas,

pamphlet, On the Mode of Communication of Cholera,

people install their own private sewage treatment plants.

suggesting that cholera is a contagious disease caused by

As populations continue to expand beyond the reach of

a poison that reproduces in the human body and is

municipal sewer systems, more families are relying on

found in the vomitus and stools of cholera patients. He

individual on-site wastewater treatment systems and

believed that the main, although not only, means of

private water supplies. The close proximity of on-site

transmission was water contaminated with this poison.

water and wastewater systems in subdivisions and other

This differed from the commonly accepted belief at the

developed areas, reliance on marginal or poor soils for

time that diseases were transmitted by inhaling vapors.

on-site wastewater disposal, and a general lack of

understanding by homeowners about proper septic tank

Treatment of Human Waste

system maintenance pose a significant threat to public

Safe, sanitary, nuisance-free disposal of wastewater is a

health. The expertise on inspecting, maintaining, and

public health priority in all population groups, small and

installing these systems generally rests with the

large, rural or urban. Wastewater should be disposed of

environmental health staff of the local county or city

in a manner that ensures that

health departments.

• community or private drinking water supplies are

not threatened;

• direct human exposure is not possible;

• waste is inaccessible to vectors, insects, rodents,

or other possible carriers;

• all environmental laws and regulations are

complied with; and

Figure 10.1. Conventional On-site Septic System [2]

Effluent leaves home through a pipe, enters a septic tank, travels through a

distribution box to a trench absorption system composed of perforated pipe.

• odor or aesthetic nuisances are not created.

Healthy Housing Reference Manual

10-1

Epidemiology

John Snow, a London physician, was among the

first to use anesthesia. It is his work in

epidemiology, however, that earned him his

reputation as a prototype for epidemiologists.

Dr. Snow’s brief 1849 pamphlet, On the Mode of

Communication of Cholera, caused no great stir, and

his theory that the city’s water supply was

contaminated was only one of many proposed

during the epidemic.

Snow, however, was able to prove his theory in

1854, when another severe epidemic of cholera

occurred in London. Through painstaking

documentation of cholera cases and correlation of

the comparative incidence of cholera among

Figure 10.2. Straight Pipe Discharge

subscribers to the city’s two water companies, he

Source: Donald Johnson; used with permission.

showed that cholera occurred much more

frequently in customers of one water company.

This company drew its water from the lower

Thames, which become contaminated with

London sewage, whereas the other company

obtained water from the upper Thames. Snow’s

evidence soon gained many converts.

A striking incident during this epidemic has become

legendary. In one neighborhood, the intersection of

Cambridge Street and Broad Street, the

concentration of cholera cases was so great that the

number of deaths reached over 500 in 10 days.

Snow investigated the situation and concluded that

the cases were clustered around the Broad Street

pump. He advised an incredulous but panicked

assembly of officials to have the pump handle

removed, and when this was done, the epidemic

was contained. Snow was a skilled practitioner as

well as an epidemiologist, and his creative use of

the scientific information of his time is an

appropriate example for those interested in disease

Figure 10.3. Clear Creek Water Contaminated With Sewage

prevention and control [3].

Source: Donald Johnson; used with permission.

In Figure 10.2, a straight pipe from a nearby home

discharges untreated sewage that flows from a shallow

into the ground or a stream. There are various processes

drainage ditch to a roadside mountain creek in which

for accomplishing this:

many children and some adults wade and fish. The clear

water (Figure 10.3) is quite deceptive in terms of the

• Centralized treatment—Publicly owned

health hazard presented. A 4-mile walk along the creek

treatment works (POTWs) that use primary

revealed 12 additional pipes that were also releasing

(physical) treatment and secondary (biologic)

untreated sewage. Some people in the area reportedly

treatment on a large scale to treat flows of up to

regard this creek as a source of drinking water.

millions of gallons or liters per day,

Raw or untreated domestic wastewater (sewage) is

• Treatment on-site—Septic tanks and absorption

primarily water, containing only 0.1% of impurities that

fields or variations thereof, and

must be treated and removed. Domestic wastewater

contains biodegradable organic materials and, very likely,

• Stabilization ponds (lagoons)—Centralized

pathogens. The primary purpose of wastewater treatment

treatment for populations of 10,000 or less when

is to remove impurities and release the treated effluent

soil conditions are marginal and land space is ample.

10-2

On-site Wastewater Treatment

Not included are pit privies and compost toilets.

placement and installation is a key to the successful

operation of any on-site wastewater treatment system, but

Historically, wastewater disposal systems are categorized as

septic tank systems have a finite life expectancy and all

water-carrying and nonwater-carrying. Nonwater-carried

such systems will eventually fail and need to be replaced.

human fecal waste can be contained and decomposed on-

Figure 10.4 shows a typical rural home with a well and a

site, the primary examples being a pit privy or compost

septic system.

toilet. These systems are not practical for individual

residences because they are inconvenient and they expose

Septic tank systems generally are composed of the septic

users to inclement weather, biting insects, and odors.

tank, distribution box, absorption field (also known as the

Because of the depth of the disposal pit for privies, they

soil drainfield), and leach field. The septic tank serves three

may introduce waste directly into groundwater. It should

purposes: sedimentation of solids in the wastewater, storage of

be noted that these types of systems are often used and

solids, and anaerobic breakdown of organic materials.

may be acceptable in low-water-use conditions such as

small campsites or along nature trails [4-6].

To place the septic tank and absorption field in a way that

will not contaminate water wells, groundwater, or streams,

On-site Wastewater Treatment Systems

the system should be 10 feet from the house and other

As urban sprawl continues and the population increases in

structures, at least 5 feet from property lines, 50 feet from

rural areas, the cost of building additional sewage disposal

water wells, and 25 feet from streams. The entire system

systems increases. One of the prime reasons for

area should be easily identifiable. There have been

annexation is to increase the tax base without increasing

occasions when owners have paved or built over the area.

the cost of municipal government. The governments

The local health code authorities must be consulted on

involved often buy into short-term tax gains at massive

required distances in their area because of soil and

long-term costs for eventual infrastructure improvements

groundwater issues.

to annexed communities. Installing septic tank systems is

common to provide on-site disposal systems, but it is a

Aerobic, or aerated, septic systems use a suspended

temporary solution at best. Because property size must be

growth wastewater treatment process, and can remove

sufficient to allow space for septic system replacement, the

suspended solids that are not removed by simple

cost to the municipality installing a centralized sewer

sedimentation. Under appropriate conditions, aerobic

system will be dramatically increased because of the large

units may also provide for nitrification of ammonia, as

lot size.

well as significant pathogen reduction. Some type of

primary treatment usually precedes the aerated tank. The

Two microbiologic processes occur in all methods that

tanks contain an aeration chamber, with either

attempt to decompose domestic wastewater: anaerobic (by

mechanical aerators or blowers, or air diffusers, and an

bacteria that do not require oxygen) and aerobic (by

area for final clarification/settling. Aerobic units may be

bacteria that require oxygen) decomposition. Aerobic

designed as either continuous flow or batch flow systems.

decomposition is generally preferred because aerobic

bacteria decompose organic matter (sewage) at a rate

much faster than do anaerobic bacteria and odors are less

likely. Centralized wastewater treatment facilities use

aerobic processes, as do most types of lagoons. Septic tank

systems use both processes.

Septic Tank Systems

Approximately 21% of American homes are served by on-

site sewage disposal systems. Of these, 95% are septic

tank field systems. Septic tank systems are used as a

means of on-site wastewater treatment in many homes,

both in rural and urban areas, in the United States. If

maintained and operated within acceptable parameters,

they are capable of properly treating wastewater for a

limited number of years and will need both routine

maintenance and eventually major repairs. Proper

Figure 10.4. Septic Tank System [7]

Healthy Housing Reference Manual

10-3

The continuous flow type are the most commercially

to install a diversion valve for annually alternating

available units. Effluent from the aerated tank is conveyed

absorption fields.

either by gravity flow or pumping to either further

treatment/ pretreatment processes or to final treatment

Absorption Field Site Evaluation

and disposal in a subsurface soil disposal system. Various

The absorption field has a variety of names, including

types of pretreatment may be used ahead of the aerobic

leach field, tile field, drainfield, disposal field, and

units, including septic tanks and trash traps.

nitrification field. The effluent from the septic tank is

directed to the absorption field for final treatment. The

The batch flow system collects and treats wastewater over

suitability of the soil, along with other factors noted

a period of time, then discharges the settled effluent at

below, determines the best way to properly treat and

the end of the cycle [8].

dispose of the wastewater.

Aerobic units may be used by individual or clustered

Most, but unfortunately not all, states require areas not

residences and establishments for treating wastewater

served by publicly owned sewers to be preapproved for

before either further treatment/pretreatment or final on-

on-site wastewater disposal before home construction

site subsurface treatment and disposal. These units are

through a permitting process. This process typically requires a

particularly applicable where enhanced pretreatment is

site evaluation by a local environmental health specialist,

important, and where there is limited availability of land

soil scientist, or, in some cases, a private contractor. To

suitable for final on-site disposal of wastewater effluent.

assist in the site evaluation process, soil survey maps from

Because of their need for routine maintenance to ensure

the local soil conservation service office may be used to

proper operation and performance, aerobic units may be

provide general information about soils in the area.

well-suited for multiple-home or commercial applications,

where economies of scale tend to reduce maintenance

The form shown in Figure 10.6 is typical of those used in

and/or repair costs per user. The lower organic and

conducting a soil evaluation.

suspended solids content of the effluent may allow a

reduction of land area requirements for subsurface

Sites for on-site wastewater disposal are first evaluated for

disposal systems.

use with a conventional septic tank system. Evaluation

factors include site topography, landscape position, soil

A properly functioning septic tank will remove

texture, soil structure, internal drainage, depth to rock or

approximately 75% of the suspended solids, oil, and

other restrictive horizons, and useable area. If the criteria

grease from effluent. Because the detention time in the

are met, a permit is issued to allow the installation of a

tank is 24 hours or less, there is not a major kill of

conventional septic tank system. Areas that do not meet

pathogenic bacteria. The bacteria will be removed in the

the criteria for a conventional system may meet less-

absorption field (drainfield). However, there are soils and

restrictive criteria for an alternative type of system.

soil conditions that prohibit the ability of a drainfield to

absorb effluent from the septic tank.

Septic tanks are sized to retain the total volume of sewage

produced by a household in a 24-hour period. Normally a

1,000-gallon tank is the minimum size to use. State or

local codes generally require larger tanks as the potential

occupancy of the home increases (e.g., 1,250 gallons for

four bedrooms) and may require two tanks in succession

when inadequate soils require alternative system

installation. Figure 10.5 shows a typical septic tank.

Distribution boxes are not required by most on-site

plumbing codes or by the U.S. Environmental Protection

Agency. When used, distribution boxes provide a

convenient inspection port. In addition, if a split system

absorption field is installed (two separate absorption

trench systems), the distribution box is a convenient place

Figure 10.5. Septic Tank [9]

10-4

On-site Wastewater Treatment

Figure 10.6. On-site Sewage Disposal System Site Evaluation Form

Many sites are unsuitable for any type of on-site

absorption field trenches should be at least 18 inches, and

wastewater disposal system because of severe topographic

ideally no deeper than 24 inches. The absorption field

limitations, poor soils, or other evaluation criteria. Such

pipe should be laid flat with no slope. There should be a

sites should not be used for on-site wastewater disposal

minimum of 12 to 18 inches of acceptable soil below the

because of the high likelihood of system failure.

bottom of the trench to any bedrock, water table, or

restrictive horizon. The length of the trench should not

Some states and localities may require a percolation test as

exceed 100 feet for systems using a distribution box.

part of the site evaluation process. As a primary

Serpentine systems may be several hundred feet long and

evaluation method, percolation tests are a poor indicator

should be filled with crushed or fragmented clean rock or

of the ability of a soil to treat and move wastewater

gravel in the bottom 6 inches of the trench. Perforated

throughout the year. However, information obtained by

4-inch-diameter pipe is laid on top of the gravel then

percolation tests may be useful when used in conjunction

covered with an additional 2 inches of rock and leveled for

with a comprehensive soil analysis.

a total of 12 inches. A geotextile material or a biodegradable

material such as straw should be placed over the gravel

Absorption Field Trench

before backfilling the trench to prevent soil from clogging

A conventional absorption field trench (Figure 10.7), also

the spaces between the rocks.

known as a rock lateral system, is the most common

system used on level land or land with moderate slopes

One or more monitoring ports should be installed in the

with adequate soil depth above the water table or other

absorption area extending to the bottom of the gravel to

restrictive horizons. The effluent from the septic tank

allow measurement of the actual liquid depth in the

flows through solid piping to a distribution box or, in many

cases, straight to an absorption field. With the conventional

system and most alternative systems, the effluent flows

through perforated pipes into gravel-filled trenches and

subsequently seeps through the gravel into the soil.

The local regulatory agency should be consulted about

the acceptable depth of the absorption field trench. Some

states require as much as 4 feet of separation beneath the

Figure 10.7. Cross-section of an Absorption Field [10]

bottom of the trench and the groundwater. The depth of

Healthy Housing Reference Manual

10-5

gravel. This is essential for subsequent testing of the

methods that can be used if regular subsurface disposal is

adequacy of the system.

not appropriate are numerous [11]. Some of the more

common alternative systems are described below.

As a general rule, using longer and narrower trenches to

meet square footage requirements produces a better

Mound Systems

working and longer lasting ground absorption sewage

A mound system (Table 10.1) is elevated above the

disposal system. Studies have shown that as septic systems

natural soil surface to achieve the desired vertical

age, the majority of effluent absorption by the soil is

separation from a water table or impervious material. The

provided by lateral movement through the trench

elevation is accomplished by placing sand fill material on

sidewalls. Longer and narrower trenches (such as 400 feet

top of the best native soil stratum. At least 1 foot of

long by 2 feet wide instead of 200 feet by 4 feet to obtain

naturally occurring soil is necessary for a mound system to

800 square feet) greatly increase the sidewall area of the

function properly. Minimizing water usage in the home also

system for lateral movement of wastewater.

is critical to prevent effluent from weeping through the

sides of the mound (Figure 10.8).

Alternative Septic Tank Systems

As the cost of land for home building increases and the

When a mound system is constructed, the septic tank

availability of land decreases, land that was once

usually receives wastewater from the house by gravity

considered unsuitable is being developed. This land often

flow. A lift station is located in the second compartment

has poor soil and drainage properties. Such sites require a

or in a separate tank to pump the effluent up to the

considerable amount of engineering skill to design an

distribution piping in the mound. Floats in the lift station

acceptable wastewater disposal system. In many cases,

control the size of the pumped effluent dose. An alarm

sites are not acceptable for seepage systems within a

should be installed to alert the homeowner of pump failure so

reasonable cost. These systems are primarily regulated by

that repairs can be made before the pump tank overfills.

state and local government and, before use, approval must

be obtained from the appropriate regulatory agencies.

Low-Pressure Pipe Systems

Even if a site is approved in one state or county jurisdiction, a

Low-pressure pipe (LPP) systems may also be used where

similar site may not be approved in another.

the soil profile is shallow. These systems are similar to

The primary difficulty with septic tank systems is treating

mounds except that they use naturally occurring soil as it

effluent in slowly permeable or marginal soils. Low-water-

exists on-site instead of elevating the disposal field with

use devices, when installed, may make it possible to use a

soil fill material. LPP systems are installed with a

small percentage of septic tank systems in marginal soil.

trenching machine at depths of 12 to 18 inches. The LPP

However, low-water-use devices are usually required as

system consists of a septic tank, high-water alarm,

part of a larger effort to develop a usable alternative

pumping tank, supply line, manifold, lateral line, and

sewage disposal system. Alternative sewage disposal

submersible effluent pump (Figure 10.9).

Table 10.1. Mound System Advantages and Disadvantages

10-6

On-site Wastewater Treatment

Figure 10.9. Low Pressure On-site System [12]

Plant-rock Filter Systems (Constructed Wetlands)

Considered experimental in some states, plant-rock filter

systems are being used with great success in Kentucky,

Louisiana, and Michigan. Plant-rock filters generally

consist of a septic tank (two-compartment), a rock filter,

and a small overflow lateral (absorption) field. Overflow

from the septic tank is directed into the rock filter. The

Figure 10.8. Mound System Cutaway [3]

rock filter is a long narrow trench (3 to 5 feet wide and

When septic tank effluent rises to the level of the pump

60 to 100 feet long) lined with leak-proof polyvinyl

control in the pumping tank, the pump turns on, and

chloride or butylplastic to which rock is added. A 2- to

effluent moves through the supply line and distribution

4-inch-diameter rock is used below the effluent flow line

laterals. The laterals contain small holes and are typically

and larger rock above (Figure10.10).

placed 3 to 8 feet apart. From the trenches, the effluent

moves into the soil where it is treated. The pump turns

Plant-rock filter systems are typically sized to allow

off when the effluent falls to the lower control. Dosing

1.3 cubic feet of rock area per gallon of total daily waste

takes place one to two times daily, depending on the

flow. A typical size for a three-bedroom house would be

amount of effluent generated. Pump malfunctions set off

468 square feet of interior area. Various width-to-length

an alarm to alert the homeowner. The time between doses

ratios within the parameters listed above could be used to

allows the effluent to be absorbed into the soil and also

obtain the necessary square footage. The trenches can

allows oxygen to reenter the soil to break down solids that

even be designed in an “L” shape to accommodate small

may be left behind. If the pump malfunctions, an alarm

building lots.

notifies the homeowner to contact a qualified septic

system contractor. The pump must be repaired or replaced

Treatment begins in the septic tank. The partially treated

quickly to prevent the pump tank from overflowing.

wastewater enters the lined plant-rock filter cell through

Table 10.2 shows the advantages and disadvantages of LPP

solid piping, where it is distributed across the cell. The

systems.

plants within the system introduce oxygen into the

Table 10.2. Low-pressure Pipe Systems Advantages and Disadvantages

Healthy Housing Reference Manual

10-7

drain field is designed for a capacity of

120 gallons per bedroom. If near capacity, systems

may not work. Water conservation will extend the

life of the system and reduce the chances of

system failure.

•

Do fix dripping faucets and leaking toilets.

•

Do avoid long showers.

•

Do use washing machines and dishwashers only

for full loads.

•

Do not allow the water to run continually when

brushing teeth or while shaving.

•

Do avoid disposing of the following items down

Figure 10.10. Plant-rock Filter System [12]

the sink drains or toilets: chemicals, sanitary

napkins, tissues, cigarette butts, grease, cooking

wastewater through their roots. As the wastewater

oil, pesticides, kitty litter, coffee grounds,

becomes oxygenated, beneficial microorganisms and fungi

disposable diapers, stockings, or nylons.

thrive on and around the roots, which leads to digestion

of organic matter. In addition, large amounts of water are

•

Do not install garbage disposals.

lost through evapotranspiration. The kinds of plants most

widely used in these systems include cattails, bulrush,

•

Do not use septic tank additives or cleaners. They

water lilies, many varieties of iris, and nutgrass. Winter

are unnecessary and some of the chemicals can

temperatures have little effect because the roots are doing

contaminate the groundwater.

the work in these systems, and they stay alive during the

winter months. Discharge from wetlands systems may

Dos and don’ts for outside maintenance:

require disinfection. The advantages and disadvantages of

the plant-rock filter system are shown in Table 10.3.

• Do maintain adequate vegetative cover over the

absorption field.

Maintaining On-site Wastewater Treatment

Systems

• Do not allow surface waters to flow over the tank

Dos and don’ts inside the house:

and drainfield areas. (Diversion ditches or

subsurface tiles may be used to direct water away

• Do conserve water. Putting too much water into

from system.)

the septic system can eventually lead to system

failure. (Typical water use is about 60 gallons per

• Do not allow heavy equipment, trucks, or

day for each person in the family.) The standard

automobiles to drive across any part of the system.

Table 10.3. Plant-rock Filter System Advantages and Disadvantages

10-8

On-site Wastewater Treatment

• Do not dig into the absorption field or build

• Buildup of aquatic weeds or algae in lakes or

additions near the septic system or the repair area.

ponds adjacent to your home. This may indicate

that nutrient-rich septic system waste is leaching

• Do make sure a concrete riser (or manhole) is

into the surface water, which may lead to both

installed over the tank if not within 6 inches of

inconvenience and possible health problems.

the surface, providing easy access for measuring

and pumping solids. (Note: All tanks should have

• Unpleasant odors around the house. Often, an

two manholes, one positioned over the inlet

improperly vented plumbing system or a failing

device and one over the outlet device.)

septic system causes a buildup of disagreeable odors.

There is no need to add any commercial substance to

Table 10.4 is a guide to troubleshooting septic tank problems.

“start” or clean a tank to keep it operating properly. They

may actually hinder the natural bacterial action that takes

Septic Tank Inspection

place inside a septic tank. The fecal material, cereal grain,

The first priority in the inspection process is the safety of

salt, baking soda, vegetable oil, detergents, and vitamin

the homeowner, neighbors, workers, and anyone else for

supplements that routinely make their way from the

which the process could create a hazard.

house to the tank are far superior to any additive.

• Do not enter septic tanks or cesspools.

Symptoms of Septic System Problems

These symptoms can mean you have a serious septic

• Do not work alone on these tanks.

system problem:

• Do not bend or lean over septic tanks or cesspools.

•

Sewage backup in drains or toilets (often a black

liquid with a disagreeable odor).

• Note and take appropriate action regarding unsafe

tank covers.

•

Slow flushing of toilets. Many of the drains will

drain much slower than usual, despite the use of

• Note unsanitary conditions or maintenance needs

plungers or drain-cleaning products. This also can

(sewage backups, odor, seepage).

be the result of a clogged plumbing vent or a

nonvented fixture.

• Do not bring sewage-contaminated clothing into

the home.

•

Surface flow of wastewater. Sometimes liquid

seeps along the surface of the ground near your

• Have current tetanus inoculations if working in

septic system. It may or may not have much of an

septic tank inspection.

odor and will range from very clear to black in

color.

Methane and hydrogen sulfide gases are produced in a

septic tank. They are both toxic and explosive. Hydrogen

•

Lush green grass over the absorption field, even

sulfide gas is quite deceptive. It can have a very strong

during dry weather. Often, this indicates that an

odor one moment, but after exposure, the odor may not

excessive amount of liquid from the system is

be noticed.

moving up through the soil, instead of down, as it

should. Although some upward movement of

Inspection Process

liquid from the absorption field is good, too

As sewage enters a septic tank, the rate of flow is reduced

much could indicate major problems.

and heavy solids settle, forming sludge. Grease and other

light solids rise to the surface, forming a scum. The

•

The presence of nitrates or bacteria in the

sludge and scum (Figure 10.11) are retained and break

drinking water well indicates that liquid from the

down while the clarified effluent (liquid) is discharged to

system may be flowing into the well through the

the absorption field.

ground or over the surface. Water tests available

from the local health department will indicate

Sludge eventually accumulates in the bottom of all septic

whether this is a problem.

tanks. The buildup is slower in warm climates than in

colder climates. The only way to determine the sludge

Healthy Housing Reference Manual

10-9

depth is to measure the sludge with a probe inserted through

Advanced Composting Systems. Phoenix

an inspection port in the tank’s lid. Do not put this job off until

composting toilet system. Whitefish, MT:

the tank fills and the toilet overflows. If this happens, damage

Advanced Composting Systems; no date. Available

to the absorption field could occur and be expensive to repair.

from URL: http://www.compostingtoilet.com.

Scum Measurement

BioLet USA, Inc. Composting toilets.

The floating scum thickness can be measured with a probe.

Newcomerstown, OH: BioLet USA, Inc.; no date.

The scum thickness and the vertical distance from the

Available from URL: http://www.biolet.com.

bottom of the scum to the bottom of the inlet can also be

measured. If the bottom of the scum gets within

3 inches

Mankl K, Slater B. Septic system maintenance.

of the outlet, scum and grease can enter the absorption

Columbus, OH: The Ohio State University

field. If grease gets into the absorption field, percolation is

Extension; no date. Available from URL:

impaired and the field can fail. If the scum is near the

http://ohioline.osu.edu/aex-fact/0740.html.

bottom of the tee, the septic tank needs to be cleaned out.

The scum thickness can best be measured through the

Hutzler NJ, Waldorf LE, Fancy J. Aerated tanks

large inspection port. Scum should never be closer than 3

(aerobic units). In: Performance of aerobic

inches to the bottom of the baffle. The scum thickness is

treatment units. Madison, WI: University of

observed by breaking through it with a probe, usually a pole.

Wisconsin - Madison; no date. Available from

URL: http://www.ci.austin.tx.us/wri/treat5.htm.

Sludge Measurement

To measure sludge, make a sludge-measuring stick using a

Center for Disease Control. Basic housing

long pole with at least 3 feet of white cloth (e.g., an old

inspection. Atlanta: US Department of Health

towel) on the end. Lower the measuring stick into the

and Human Services; 1976.

tank, behind the outlet baffle to avoid scum particles,

until it touches the tank bottom. It is best to pump each

10. Purdue Research Foundation. Environmental

tank every 2 to 3 years. Annual checking of sludge level is

education software series. West Lafayette, IN:

recommended. The sludge level must never be allowed to

Purdue Research Foundation; 1989. Available

rise within 6 inches of the bottom of the outlet baffle. In

from URL: http://www.inspect-ny.com/

two-compartment tanks, be sure to check both compartments.

septic/trench.gif.

When a septic tank is pumped, there is no need to

deliberately leave any residual solids. Enough will remain

11. North Carolina Cooperative Extension Service.

after pumping to restart the biologic processes.

On-site wastewater treatment websites.

Jacksonville, NC: North Carolina Cooperative

References

Extension Service; 2002. Available from URL:

1. University of California Cooperative Extension,

http://www.ces.ncsu.edu/onslow/staff/drashash/

Calaveras County. Septic tanks: the real poop. San

enved/sepsites.html.

Andreas, CA: University of California Cooperative

Extension, Calaveras County; no date. Available

12. Clay Township Regional Waste District. Septic

from URL: http://cecalaveras.ucdavis.edu/realp.htm.

systems. Indianapolis: Clay Township Regional

Waste District; 2004. Available from URL:

2. University of Nebraska-Lincoln. Residential on-

http://www.ctrwd.org/septics.htm.

site wastewater treatment: septic system and

drainfield maintenance. Lincoln, NE: University

13. Jackson Purchase Resource Conservation and

of Nebraska-Lincoln; 2000. Available from URL:

Development Foundation, Inc. Septic systems: an

http://ianrpubs.unl.edu/wastemgt/g1424.htm.

overview. Cynthiana, KY: Jackson Purchase Resource

Conservation and Development Foundation, Inc.;

3. Rosenberg CE. The cholera years. Chicago: The

no date. Available from URL:

University of Chicago Press; 1962.

http://www.jpf.org/LRV/septic.htm.

4. Salvato J, Nemerow NL, Agardy FJ, editors.

Environmental engineering. 5th ed. New York:

John Wiley and Sons; 2003.

Healthy Housing Reference Manual

10-11

Chapter 11: Electricity

'“To electrize plus or minus, no more needs to be known

installation is not necessarily safe and adequate today. An

than this, that the parts of the tube or sphere that are

example would be the grounding of a home electrical

rubbed, do, in the instant of the friction, attract the

system. In the past, electrical systems could be grounded

electrical fire, and therefore take it from the thing rubbing;

to the home’s plumbing system. Today, many plumbing

the same parts immediately, as the friction upon them ceases,

systems are no longer constructed of conductive material,

are disposed to give the fire they have received to any body.”

but are made of plastic or polyvinyl chloride-based

materials. Today, the recommendations for grounding a

Benjamin Franklin

home electrical system are to use two 8-foot by 5/8-inch

Franklin’s Discovery of the Positive

copper ground rods. These must be spaced 6 feet apart

and Negative States of Electricity, 1747

and be connected by a continuous (unbroken) piece of

copper wire (the size of this wire corresponds to the size

Introduction

of the system main). It is also highly recommended that

Two basic codes concerned with residential wiring are

the system be grounded to the incoming water line if it is

important to the housing inspector. The first is the local

conductive or to the nearest conductive cold water

electrical code. The purpose of this code is to safeguard

supply line. Hazards often occur because of overloading

persons as well as buildings and their contents from

wiring systems or usage not in conformity with the code.

hazards arising from the use of electricity for light, heat,

This occurs because initial wiring did not provide for

and power. The electrical code contains basic minimum

increases in the use of electricity. For this reason, it is

provisions considered necessary for safety. Compliance

recommended that initial installations be adequate and

with this code and proper maintenance will result in an

that reasonable provisions for system changes be made

installation essentially free from hazards, but not

for further increases in the use of electricity.

necessarily efficient, convenient, or adequate for good

service or future expansion.

The other code that contains electrical provisions is the

local housing code. It establishes minimum standards for

Most local electrical codes are modeled after the National

artificial and natural lighting and ventilation, specifies

Electrical Code, published by the National Fire

the minimum number of electric outlets and lighting

Protection Association (NFPA). Reference to the “code”

fixtures per room, and prohibits temporary wiring except

in the remainder of this chapter will be to the National

under certain circumstances. In addition, the housing

Electrical Code, unless specified otherwise [1].

code usually requires that all components of an electrical

system be installed and maintained in a safe condition to

An electrical installation that was safe and adequate

prevent fire or electric shock.

under the provisions of the electrical code at the time of

Definitions of Terms Related to Electricity

Ampere—The unit for measuring intensity of flow of electricity. Its symbol is “I.”

Bonding—Applies inert material to metal surfaces to eliminate electrical potential between metal components and

prevent components and piping systems from having an elevated voltage potential.

Circuit—The flow of electricity through two or more wires from the supply source to one or more outlets and back to the

source.

Circuit breaker—A safety device used to break the flow of electricity by opening the circuit automatically in the event of

overloading or used to open or close the circuit manually.

Conductor—Any substance capable of conveying an electric current. In the home, copper wire is usually used.

• A bare conductor is one with no insulation or covering.

• A covered conductor is one covered with one or more layers of insulation.

Healthy Housing Reference Manual

11-1

Flow of Electric Current

This high-transmission voltage is stepped down (reduced)

Electricity is usually created by a generator that converts

to normal 115/230-volt household current by a transformer

mechanical energy into electrical energy. The electricity

located near the point of use (residence). The electricity is

may be the result of water, steam, or wind powering or

then transmitted to the house by a series of wires called a

turning a generator. The electricity is then run through a

service drop. In areas where the electric wiring is underground,

transformer, where voltage is increased to several hundred

the wires leading to the building are buried in the ground.

thousand volts and, in some instances, to a million or

more volts. This high voltage is necessary to increase the

For electric current to flow, it must travel from a higher

efficiency of power transmission over long distances.

to a lower potential voltage. In an electrical system, the

Definitions of Terms Related to Electricity

Conductor gauge—A numeric system used to label electric conductor sizes, given in American Wire Gauge (AWG). The

larger the AWG number, the smaller the wire size.

Current—The flow of electricity through a circuit.

• Alternating current is an electric current that reverses its direction of flow at regular intervals. For example, it

would alternate 60 times every second in a 60-cycle system. This type of power is commonly found in homes.

• Direct current is an electric current flowing in one direction. This type of current is not commonly found in

today’s homes.

Electricity—Energy that can be used to run household appliances; it can produce light and heat, shocks, and numerous

other effects.

Fuse—A safety device that cuts off the flow of electricity when the current flowing through the fuse exceeds its rated

capacity.

Ground—To connect with the earth, as to ground an electric wire directly to the earth or indirectly through a water pipe

or some other conductor. Usually, a green-colored wire is used for grounding the whole electrical system to the earth. A

copper wire is usually used to ground individual electrical components of the whole system. (The home inspector should

never assume that insulation color wiring codes have been used appropriately.)

Ground fault circuit interrupter (GFCI)—A device intended to protect people from electric shock. It de-energizes a

circuit or portion of a circuit within an established very brief period of time when a current to ground exceeds some

predetermined value (less than that required to operate the over-current protected device of the supply circuit).

Hot wires—Those that carry the electric current or power to the load; they are usually black or red.

Insulator—A material that will not permit the passage of electricity.

Kilowatt-hour (KWH)—The amount of energy supplied by one kilowatt (1,000 watts) for 1 hour (3,600 seconds), equal

to 3,600,000 joule. Electric bills are usually figured by the number of KWHs consumed.

Neutral wire—The third wire in a three-wire distribution circuit; it is usually white or light gray and is connected to the

ground.

Resistance—A measure of the difficulty of electric current to pass through a given material; its unit is the ohm.

Service—The conductor and equipment for delivering energy from the electricity supply system to the wiring system of

the premises.

Service drop—The overhead service connectors from the last pole or other aerial support to and including the splices, if

any, connecting to the service entrance conductors at the building or other structure.

Service panel—Main panel or cabinet through which electricity is brought to the building and distributed. It contains the

main disconnect switch and fuses or circuit breakers.

Short circuit—A break in the flow of electricity through a circuit due to the load caused by improper connection between

hot and neutral wires.

Volt—The unit for measuring electrical pressure of force, which is known as electromotive force. Its symbol is “E.”

Voltage drop—A voltage loss when wires carry current. The longer the cord, the greater the voltage drop.

Watt—The unit of electric power. Volts times amperes = watts.

11-2

Electricity

hot wires (black or red) are at a higher potential than are

because it is closer to the building. The equipment

the neutral or ground wire (white or green).

ground protects people from potential harm during the

use of certain electrical equipment. The system ground

Voltage is a measure of the force at which electricity is

should be a continuous wire of low resistance and of

delivered. It is similar to pressure in a water supply system.

sufficient size to conduct current safely from lightning

and overloads.

Current is measured in amperes and is the quantity of

flow of electricity. It is similar to measuring water in

Electric Service Entrance

gallons per second. A watt is equal to volts times amperes.

Service Drop

It is a measure of how much power is flowing. Electricity

To prevent accidental contact by people, the entrance

is sold in quantities of kilowatt-hours.

head (Figure 11.2) should be attached to the building at

least 10 feet above ground. The conductor should clear all

The earth, by virtue of moisture contained within the

roofs by at least 8 feet and residential driveways by 12 feet.

soil, serves as a very effective conductor. Therefore, in

For public streets, alleys, roads, and driveways on other than

power transmission, instead of having both the hot and

residential property, the clearance must be 18 feet.

neutral wires carried by the transmission poles, one lead

of the generator is connected to the ground, which serves

The wires or conductor should be of sufficient size to carry

as a conductor (Figure 11.1). All electrical utility wires are

the load and not smaller than No. 8 copper wire or equivalent.

carried by the transmission towers and are considered hot

or charged. At the house, or point where the electricity is

For connecting wire from the entrance head to the service

to be used, the circuit is completed by another

drop wires, the code requires that the service entrance

connection to ground.

conductors be installed either below the level of the

service head or below the termination of the service

The electric power utility provides a ground somewhere

entrance cable sheath. Drip loops must be formed on

in its local distribution system; therefore, there is a

individual conductors. This will prevent water from

ground wire in addition to the hot wires within the

entering the electric service system. The wires that form

service drop. In Figure 11.1 this ground can be seen at

the entrance cable should extend 36 inches from the

the power pole that contains the step-down transformer.

entrance head to provide a sufficient length to connect

service drop wires to the building with insulators. The

In addition to the ground connection provided by the

entrance cable may be a special type of armored outdoor

electric utility, every building is required to have an

cable, or it may be enclosed in a conduit. The electric

independent ground called a system ground. The system

power meter may be located either inside or outside the

ground is a connection to ground from one of the

current-carrying conductors of the electrical system.

System grounding, applied to limit overvoltages in the

event of a fault, provides personnel safety, provides a

positive means of detecting and isolating ground faults,

and improves service reliability. Therefore, the system

ground’s main purpose is to protect the electrical system

itself and offers limited protection to the user.

The system ground serves the same purpose as the power

company’s ground; however, it has a lower resistance

Figure 11.1. Utility Overview [2]

Figure 11.2. Entrance Head

Healthy Housing Reference Manual

11-3

building. In either instance, the meter must be located

Underground Service

before the main power disconnect.

When wires are run underground, they must be protected

from moisture and physical damage. The opening in the

Figure 11.3 shows an armored cable service entrance with

building foundation where the underground service enters

a fuse system. Newer construction will have circuit

the building must be moisture proof. Refer to local codes

breakers, as shown in Figure 11.4. The armored cable is

for information about allowable materials for this type of

anchored to the building with metal straps spaced every

service entrance.

4 feet. The cable is run down the wall and through a hole

drilled through the building. The cable is then connected to

Electric Meter

the service panel, which should be located within 1 foot of

The electric meter (Figure 11.6) may be located inside or

where the cable enters the building. The ground wire

outside the building. The meter itself is weatherproof and

need not be insulated. This ground wire may be either

is plugged into a weatherproof socket. The electric power

solid or stranded copper, or a material with an equivalent

company furnishes the meter; the socket may or may not

resistance.

be furnished by the power company.

Figure 11.5 shows the use of thin-wall conduit in a service

Grounding

entrance.

The system ground consists of grounding the neutral

incoming wire and the neutral wire of the branch circuits.

The equipment ground consists of grounding the metal

parts of the service entrance, such as the service switch, as

well as the service entrance conduit, armor or cable.

Figure 11.3. Armored Cable Service Entrance [2]

Figure 11.4. Breakers [2]

Figure 11.5. Thin-wall Conduit [2]

11-4

Electricity

Poor grounding at any point can result in a person

Figure 11.8 shows a typical grounding scheme at the

providing a more effective route to ground than the

service box of a residence. In this figure, only the

intended ground, resulting in electrocution. This can

grounded neutral wires are shown. The neutral strap is a

occur from damaged insulation allowing electricity to

conductive bare metal strip that is riveted directly to the

flow into the case or cabinet of the appliance.

service box. This conductive strip forms a collective

ground that joins the ground wires from the service

The system must be grounded by two 8 foot by 5/8-inch

entrance, branch circuits, and house ground.

copper ground rods of at least 8 feet in length driven into

the ground and connected by a continuous (unbroken)

Follow these key grounding points:

piece of copper wire (the size of this wire corresponds to

the size of the system main). It is highly recommended

•

Use two metal rods driven 8 feet into the ground.

that the system also be grounded to the incoming water line

or nearest cold water supply line if it is metal.

•

Bond around water heaters and filters to assure

grounding.

The usual ground connection is to a conductive water

pipe of the city water system. The connection should be

•

If water pipes are used, they must be supplement-

made to the street side of the water meter, as shown in

ed with a second ground.

Figure 11.7. If the water meter is located near the street

curb, then the ground connection should be made to the

•

Ground rod must be driven to full depth.

cold water pipe as close as possible to where it enters the

building. It is not unusual for a water meter to be

•

If ground rod resistance exceeds 25 ohms, install

removed from the building for service. If the ground

two rods at a minimum of 6 feet apart.

connection is made at a point in the water piping system

on the building side of the water meter, the ground

•

When properly grounded, the metal frame of a

circuit will be broken on removal of the meter. This

building can be used as a ground point.

broken ground circuit is a shock hazard if both sides of

the water meter connections are touched simultaneously.

•

Do not use underground gas lines as a ground.

Local or state codes should be checked to determine

compliance with correct grounding protocols.

•

Provide external grounds to other systems such as

satellite, telephone, and other services to further

In increasing instances, the connections between the

protect the electrical system from surges.

water meters and pipes are electrically very poor. In this

case, if the ground connection is made on the building

side of the water meter, there may not be an effective

ground. To prevent the two aforementioned situations,

the code requires effective bonding by a properly sized

jumper-wire around any equipment that is likely to be

disconnected for repairs or replacement.

Often, the house ground will be disconnected. Therefore,

the housing inspector should always check the house

ground to see if it is properly connected.

Figure 11.6. Electric Meter

Figure 11.7. Typical Service Entrance [2]

Healthy Housing Reference Manual

11-5

for small appliances and electric lights. The result is a

doubling of the number of circuits, and, possibly, a

corresponding increase in the number of branch circuits,

with a reduction in the probability of fire caused by

overloading electrical circuits if the electrical demands

exceed the capacity.

Residential Wiring Adequacy

The use of electricity in the home has risen sharply since

the 1930s. Many homeowners have failed to repair or

improve their wiring to keep it safe and up to date. In the

1970s, the code recommended that the main distribution

panel in a home be a minimum of 100 amps. Because the

number of appliances that use electricity has continued to

grow, so has the size of recommended panels. For a

normal house (2,500 to 3,500 square feet), a 200-amp

panel is recommended. The panel must be of the breaker

type with a main breaker for the entire system (Figure 11.4).

Figure 11.8. Grounding Scheme [2]

Fuse boxes are not recommended for new housing.

• If the water service pipes to the home are not

This type of service is sufficient in a one-family house or

metal or if all of the service components in the

dwelling unit to provide safe and adequate electricity for

home are not metal, then the water system cannot

the lighting, refrigerator, iron, and an 8,000-watt cooking

play a role in grounding.

range, plus other appliances requiring a total of up to

10,000 watts.

Bonding is necessary to provide a route for electricity to

flow around isolated elements of a piping system to

Some older homes have a 60-ampere, three-wire service

ensure electrical potential is minimized for both the

(Figure 11.10). It is recommended that these homes be

protection of the system from corrosion and to protect

rewired for at least the minimum of 200-amperes

individuals from electrical shock.

recommended in the code. The 60-amp service is safely

capable of supplying current for only lighting and

Two- or Three-wire Electric Services

portable appliances, such as a cooking range and regular

One of the wires in every electrical service installation is

dryer (4,500 watts), or an electric hot water heater

supposed to be grounded. This neutral wire should always

(2,500 watts), and cannot handle additional major

be white. The hot wires are usually black, red, or some

appliances. Other older homes today have only a 30-ampere,

other color, but never white.

115-volt, two-wire service (Figure 11.11). This system can

safely handle only a limited amount of lighting, a few

The potential difference or voltage between the hot wires

minor appliances, and no major appliances. Therefore,

and the ground or neutral wire of a normal residential

this size service is substandard in terms of the modern

electrical system is 115 volts. Thus, where there is a two-

household’s needs for electricity. Furthermore, it is a fire

wire installation (one hot and one neutral), only 115 volts

hazard and a threat to the safety of the home and the

are available.

occupants.

When three wires are installed (two hot and one neutral),

either 115 or 230 volts are available. In a three-wire

system, the voltage between the neutral and either of the

hot wires is 115 volts; between the two hot wires, it is

230 (Figure 11.9). The major advantage of a three-wire

system is that it permits the operation of heavy electrical

equipment such as clothes dryers, cooking ranges, and air

conditioners, the majority of which require 230-volt

circuits. In addition, the three-wire system is split at the

service panel into two 115-volt systems to supply power

Figure 11.9. Grounding [2]

11-6

Electricity

Wire Sizes and Types

Reducing Risk

Aluminum wiring, used in some homes from the mid

Only two remedies for aluminum wiring have been

1960s to the early 1970s, is a potential fire hazard [3].

recommended by the CPSC: discontinued use of the

According to the U.S. Consumer Product Safety

aluminum circuit or the less costly option of adding

Commission (CPSC), fires and even deaths have been

copper connecting “pigtail” wires between the aluminum

caused by this hazard. Problems due to expansion can

wire and the wired device (receptacle, switch, or other

cause overheating at connections between the wire and

device). The pigtail connection must be made using only

devices (switches and outlets) or at splices. CPSC research

a special connector and special crimping tool licensed by

shows that homes wired with aluminum wire

the AMP Corporation. Emergency temporary repairs

manufactured before 1972 are 55 times more likely to

necessary to keep an essential circuit in service might be

have one or more connections reach fire hazard

possible following other procedures described by the

conditions than are homes wired with copper. Post-1972

CPSC, and in accordance with local electrical codes [4,5].

aluminum wire is also a concern. Introduction of

aluminum wire alloys around 1972 did not solve most of

Wire Sizes

the connection failure problems. Aluminum wiring is still

Electric power actually flows along the surface of the wire.

permitted and used for certain applications, including

It flows with relative ease (little resistance) in some materials,

residential service entrance wiring and single-purpose

such as copper and aluminum, and with a substantial

higher amperage circuits such as 240-volt air conditioning

amount of resistance in iron. If iron wire were used, it

or electric range circuits.

would have to be 10 times as large as copper wire to be as

effective in conducting electricity. In fine electronics, gold

is the preferred conductor because of the resistance to

corrosion and the very high conductivity.

Electricity is the movement of electrons from an area of

higher potential to one of lower potential. An analogy to

how electricity flows would be the flow of water along the

path of least resistance or down a hill. All it takes to

create the potential for electricity is the collection of

Figure 11.10. Three-wire Service [2]

Figure 11.11. Two-wire Service [2]

Healthy Housing Reference Manual

11-7

Maximum Current Recommended for AWG Wire Size

Size wire (AWG) (larger wire, smaller number)

#14

#12

#10

Maximum capacity in amperes

electrons and a pathway for them to flow to an area of

Wire Types

lesser concentration along a conductor. When a person

All wires must be marked to indicate the maximum

walks across a nylon carpet in times of low atmospheric

working voltage, the proper type letter or letters for the

humidity, his or her body will often collect electrons and

type wire specified in the code, the manufacturer’s name

serve as a capacitor (a storage container for electrons).

or trademark, and the AWG size or circular-mil area

When that person nears a grounding source, the electrons

(Figure 11.12). A variety of wire types can be used for a

will often jump from a finger to the ground, creating a

wide range of temperature and moisture conditions. The

spark and small shock.

code should be consulted to determine the proper wire

for specific conditions.

A number preceded by the letters AWG (American Wire

Gauge) indicates copper wire sizes [6]. As the AWG

Types of Cable

number of the wire becomes smaller, the size and current

Nonmetallic sheathed cable consists of wires wrapped in

capacity of the wire increases. AWG 14 is most

plastic and then a paper layer, followed by another spiral

commonly found in older residential branch circuits.

layer of paper, and enclosed in a fabric braid, which is

AWG 14 wires should be used only in a branch circuit

treated with moisture- and fire-resistant compounds.

with a 15-ampere capacity or no more than a 1,500-watt

Figure 11.12 shows this type of cable, which often is

demand. Wire sizes AWG 16, 18, and 20 are progressively

marketed under the name Romex. This type of cable can

smaller than AWG 14 and are used for extension wires or

be used only indoors and in permanently dry locations.

low-voltage systems. Wire of the correct size must be used

Romex-type wiring is normally used in residential

for two reasons: current capacity and voltage drop or loss.

construction. However, when cost permits, it is

recommended that a conduit-based system be used.

When current flows through a wire, it creates heat. The

greater the amount of flow, the greater the amount of

Armored cable is commonly known as BX or Flexsteel

heat generated. (Doubling the amperes without changing

trade names. Wires are wrapped in a tough paper and

the wire size increases the amount of heat by four times.)

covered with a strong spiral flexible steel armor. This type

The heat is electric energy (electrons) that has been

of cable is shown in Figure 11.13 and may be used only

converted into heat energy by the resistance of the wire.

in permanently dry indoor locations. Armored cable must

The heat created by the coils in a toaster is an example of

be supported by a strap or staple every 6 feet and within

designed resistance to create heat. Most heat developed by

24 inches of every switch or junction box, except for

an electrical conductor is wasted; therefore, the electric

concealed runs in old work where it is impossible to

energy used to generate it is also wasted.

mount straps.

If the amount of heat generated by the flow of current

Cables are also available with other outer coatings of metals,

through a wire becomes excessive, a fire may result.

such as copper, bronze, and aluminum for use in a variety of

Therefore, the code sets the maximum permissible current

conditions.

that may flow through a certain type and size wire. The

blue box provides examples of current capacities for

copper wire of various sizes.

In addition to heat generation, there will be a reduction in

voltage as a result of attempting to force more current

through a wire than it is designed to carry. Certain

appliances, such as induction-type electric motors, may be

damaged if operated at too low a voltage.

Figure 11.12. Wire Markings [2]

11-8

Electricity

Voluntary industry safety standards, including those of

Underwriter’s Laboratory (UL), now require that general-

use extension cords have safety closures, warning labels,

rating information about the electrical current, and other

features for the protection of children and other

Figure 11.13. Armored Cable [2]

consumers.

Flexible Cords

CPSC estimates that about 4,000 injuries associated with

In addition, UL-listed extension cords now must be

electric extension cords are treated in hospital emergency

constructed with 16-gauge or larger wire or be equipped

rooms each year. About half of the injuries involve

with integral fuses. The 16-gauge wire is rated to carry

fractures, lacerations, contusions, or sprains from people

13 amperes (up to 1,560 watts), as compared with the

tripping over extension cords. Thirteen percent of the

formerly used 18-gauge cords that were rated for

injuries involve children younger than 5 years of age;

10 amperes (up to 1,200 watts).

electrical burns to the mouth account for half the injuries

to young children [7].

Safety Suggestions

The following are CPSC recommendations [7] for

CPSC also estimates that about 3,300 residential fires

purchasing and safely using extension cords:

originate in extension cords each year, killing 50 people

and injuring about 270 others [7]. The most frequent

•

Use extension cords only when necessary and only

causes of such fires are short circuits, overloading the

on a temporary basis.

system, and damage to or misuse of extension cords.

•

Use polarized extension cords with polarize

The Problem

appliances.

Following are CPSC investigations of injuries that

illustrate the major injury patterns associated with

•

Make sure cords do not dangle from the counter

extension cords: children putting extension cords in their

or tabletops where they can be pulled down or

mouths, overloaded cords, worn or damaged cords, and

tripped over.

tripping over cords:

•

Replace cracked or worn extension cords with

• A 15-month-old girl put an extension cord in her

new 16-gauge cords that have the listing of a

mouth and suffered an electrical burn. She

nationally recognized testing laboratory, safety

required surgery.

closures, and other safety features.

• Two young children were injured in a fire caused

•

With cords lacking safety closures, cover any

by an overloaded extension cord in their family’s

unused outlets with electrical tape or with plastic

home. A lamp, TV set, and electric heater had

caps to prevent the chance of a child making

been plugged into a single, light-duty extension

contact with the live circuit.

cord.

•

Insert plugs fully so that no part of the prongs is

• A 65-year-old woman was treated for a fractured

exposed when an extension cord is in use.

ankle after tripping over an extension cord.

•

When disconnecting cords, pull the plug rather

The Standards

than the cord itself.

The code says that many cord-connected appliances

should be equipped with polarized grounding plugs.

•

Teach children not to play with plugs and outlets.

Polarized plugs can only be inserted one way into the

outlet because one blade is slightly wider than the other.

•

Use only three-wire extension cords for appliances

Polarization and grounding ensure that certain parts of

with three-prong plugs. Never remove the third

appliances that could have a higher risk of electric shock

(round or U-shaped) prong, which is a safety

when they become live are instead connected to the

feature designed to reduce the risk for shock and

neutral, or grounded, side of the circuit. Such electrical

electrocution.

products should only be used with polarized or grounded

extension cords.

Healthy Housing Reference Manual

11-9

•

In locations where furniture or beds may be

Concealed Knob and Tube Wiring

pushed against an extension cord where the cord

Concealed knob and tube wiring is a wiring method

joins the plug, use a special angle extension cord

using knobs, tubes, and flexible nonmetallic tubing for

specifically designed for use in these instances.

the protection and support of insulated wires concealed in

hollow spaces of walls and ceilings of buildings. This

•

Check the plug and the body of the extension

wiring method is similar to open wiring and, like open

cord while the cord is in use. Noticeable warming

wiring, is usually found only in older buildings.

of these plastic parts is expected when cords are

being used at their maximum rating. If the cord

Electric Service Panel

feels hot or if there is a softening of the plastic,

The service switch is a main switch that will disconnect

this is a warning that the plug wires or

the entire electrical system at one time. The main fuses or

connections are failing and that the extension

circuit breakers are usually located within the service

cord should be discarded and replaced.

switch box. The branch circuit fuse or circuit breaker may

also be located within this box.

•

Never use an extension cord while it is coiled or

looped. Never cover any part of an extension cord

According to the code, the switch must be externally

with newspapers, clothing, rugs, or any objects

operable. This condition is fulfilled if the switch can be

while the cord is in use. Never place an extension

operated without the operator being exposed to

cord where it is likely to be damaged by heavy

electrically active parts. Figure 11.14 shows a 200-amp

furniture or foot traffic.

service box. Figure 11.15 shows an external “hinged

switch” power shutoff installed on the outside of a home.

•

Do not use staples or nails to attach extension

cords to a baseboard or to another surface. This

Most of today’s older homes do not have hinged switches.

could damage the cord and present a shock or fire

Instead, the main fuse is mounted on a small insulated

hazard.

block that can be pulled out of the switch. When this

block is removed, the circuit is broken.

•

Do not overload extension cords by plugging in

appliances that draw a total of more watts than

In some installations, the service switch is a “solid

the rating of the cord.

neutral” switch, meaning that the switch or a fuse does

not break the neutral wire in the switch.

•

Use special heavy-duty extension cords for high-

wattage appliances such as air conditioners,

When circuit breakers are used in homes instead of fuses,

portable electric heaters, and freezers.

main circuit breakers may or may not be required. If it

takes more than six movements of the hand to open all

•

When using outdoor tools and appliances, use

the branch-circuit breakers, a main breaker, switch, or

only extension cords labeled for outdoor use.

fuse will be required ahead of the branch-circuit breakers.

Thus, a house with seven or more branch circuits requires

Wiring

a separate disconnect means or a main circuit breaker

Open Wiring

ahead of the branch-circuit breakers.

Open wiring is a wiring method using knobs, nonmetallic

tubes, cleats, and flexible tubing for the protection and

Over-current Devices

support of insulated conductors in or on buildings and

The amperage (current flow) in any wire is limited to the

not concealed by the structure. The term “open wiring”

maximum permitted by using an over-current device of a

does not mean exposed, bare wiring. In dry locations,

size specified by the code. Four types of over-current

when not exposed to severe physical damage, conductors

devices are common: circuit breakers, ground fault circuit

may be separately encased in flexible tubing. Tubing

interrupters (GFCIs), arc fault circuit interrupters

should be in continuous lengths not exceeding 15 feet

(AFCIs), and fuses. The over-current device of a specific

and secured to the surface by straps not more than

size is specified by the code. The over-current device must

4½ feet apart. Tubing should be separated from other

be rated at equal or lower capacity than the wire of the

conductors by at least 2½ inches and should have a

circuit it protects.

permanently maintained airspace between them and any

and all pipes they cross.

11-10

Electricity

Circuit Breakers (Fuseless Service Panels)

• A 20-ampere circuit for small appliances and

A circuit breaker looks something like an ordinary electric

power tools.

light switch. Figure 11.14 shows the service box in a 200-

amp fuseless system. Figure 11.15 shows a service switch.

• A 15-ampere circuit for general-purpose lighting,

There is a handle that may be used to turn power on or

TVs, VCRs, computers, and vacuum cleaners.

off. Inside is a simple mechanism that, in case of a circuit

overload, trips the switch and breaks the circuit. The

• Space for new circuits to be added if needed for

circuit breaker may be reset by turning the switch to off

future use.

and then simply resetting the switch to the on position. A

circuit breaker is capable of taking harmless short-period

Ground Fault Circuit Interrupters

overloads (such as the heavy initial current required in the

Unlike circuit breakers and fuses, GFCIs are installed to

starting of a washing machine or air conditioner) without

protect the user from electrocution. These devices provide

tripping, but protects against prolonged overloads. After

protection against electrical shock and electrocution from

the cause of trouble has been located and corrected, power

ground faults or contact with live parts by a grounded

is easily restored. Fuseless service panels or breaker boxes are

individual. They constantly monitor electrical currents

usually broken up into the following circuits:

flowing into a product. If the electricity flowing through

the product differs even slightly from that returning, the

• A 100-ampere or larger main circuit breaker that

GFCI will quickly shut off the current. GFCIs detect

shuts off all power.

amounts of electricity much smaller than those required

for a fuse or circuit breaker to activate and shut off the

• A 40-ampere circuit for an appliance such as an

circuit. UL lists three types of GFCIs designed for home

electric cooking range.

use that are readily available and fairly inexpensive and

simple to install:

• A 30-ampere circuit for a clothes dryer, water

heater, heat pump, or central air conditioning.

• Wall Receptacle GFCI—This type of GFCI

(Figure 11.16) is used in place of a standard

receptacle found throughout the house. It fits into

a standard outlet box and protects against ground

faults whenever an electrical product is plugged

into the outlet. If strategically located, it will also

provide protection to downstream receptacles.

• Circuit Breaker GFCI—In homes equipped with

circuit breakers, this type of GFCI may be

installed in a panel box to protect selected circuits.

A circuit breaker GFCI serves a dual purpose: it

shuts off electricity in the event of a ground fault

Figure 11.14. 200-Amp Service Box

Figure 11.15. External Power Shutoff and Meter

Healthy Housing Reference Manual

11-11

and will also trip when a short circuit or an

for fire increases. It is estimated that about one third of

overload occurs.

fires are caused by arcing faults. Normal fuses and circuit

breakers are not capable of detecting arc faults and therefore

• Portable GFCI—A portable GFCI requires no

will not open the circuit and stop the flow of electricity.

special knowledge or equipment to install. One

type contains the GFCI circuitry in a self-

Fused Ampere Service Panel (Fuse Box)

contained enclosure with plug blades in the back

Fuse-type panel boxes are generally found in older homes.

and receptacle slots in the front. It can be plugged

They are as safe and adequate as a circuit breaker of

into a receptacle, and the electrical product

equivalent capacity, provided fuses of the proper size are used.

plugged into the GFCI. Another type of portable

GFCI is an extension cord combined with a

A fuse, like a circuit breaker, is designed to protect a

GFCI. It adds flexibility in using receptacles that

circuit against overloading and short circuits and does so

are not protected by GFCIs.

in two ways.

Once a GFCI is installed, it must be checked monthly to

When a fuse is blown by a short circuit, the metal strip is

determine that it is operating properly. Pressing the test

instantly heated to an extremely high temperature, and

button can check units; the GFCI should disconnect the

this heat causes it to vaporize. A fuse blown by a short

power to that outlet. Pressing the reset button reconnects

circuit may be easily recognized because the window of

the power. If the GFCI does not disconnect the power,

the fuse usually becomes discolored.

have it checked by a qualified, certified electrician.

GFCIs should be installed on circuits in the following

In a fuse blown by an overload, the metal strip is melted

areas: garages, bathrooms, kitchens, crawl spaces,

at its weakest point, breaking the flow of current to the

unfinished basements, hot tubs and spas, pool electronics,

load. In this case, the window of the fuse remains clear;

and exterior outlets. However, they are not required on

therefore, a blown fuse caused by an overload may also be

single outlets that serve major appliances.

easily recognized.

Arc-fault Circuit Interrupters

Sometimes, although a fuse has not been blown, the

Arc-fault circuit interrupters are new devices intended to

bottom of the fuse may be severely discolored and pitted.

provide fire protection by opening the circuit if an arcing

This indicates a loose connection because the fuse was not

fault is detected. An arcing fault is an electric spark or hot

screwed in properly.

plasma field that extends from the hot wire to a ground.

An arc is a luminous discharge of electricity across an

It is critical to check that all fuses are properly rated for

insulating medium or simply a spark across an air gap.

the designed amperage. The placing of a fuse with a

Arcs occur every day in homes. For example, an arc

higher amperage than recommended presents a significant

occurs inside the switch when a light is turned on. Toy

fire hazard.

racecars and trains create arcs. The motors inside hair

dyers and power drills have tiny arcs. All of these are

Generally, all fused panel boxes are wired similarly for

controlled arcs. It is the

two- and three-wire systems. In a two-wire-circuit panel

uncontrolled or nondesigned

box, the black or red hot wire is connected to a terminal

arc that is a serious fire hazard

of the main disconnect, and the white or light gray

in the home. The arc-fault

neutral wire is connected to the neutral strip, which is then

circuit interrupter looks like

grounded to the pipe on the street side of the water meter.

the GFCI unit (Figure 11.17),

but it is not designed to

In a three-wire system, the

protect against electric shock.

black and red hot wires are

connected to separate

Because most electrical wiring

terminals of the main

in a home is hidden from

disconnect, and the neutral

view, many arc faults go

wire is grounded the same as

undetected and continue

for a two-wire system. Below

arcing indefinitely. If left in

each fuse is a terminal to

Figure 11.16. GFCI

this arcing state, the potential

which a black or red wire is

Figure 11.17. Arc Interrupter

11-12

Electricity

connected. The white or light gray neutral wires are then

electric circuit that supplies current to a limited number

connected to the neutral strip. Each fuse indicates a

of outlets and fixtures. A residence generally has many

separate circuit (Figure 11.18).

branch circuits. Each is protected against short circuits

and overloads by a 15- or 20-ampere fuse or circuit breaker.

•

Nontamperable fuses—All ordinary plug fuses

have the same diameter and physical appearance,

The number of outlets per branch circuit varies from

regardless of their current capacity, whereas

building to building. The code requires enough light

nontamperable fuses are sized by amperage load.

circuits so that 3 watts of power will be available for each

Thus, with regular fuses, if a circuit designed for a

square foot of floor area in a house. A circuit wired with

15-ampere fuse is overloaded so that the 15-ampere

14-gauge wire and protected by a 15 ampere over-current

fuse blows out, nothing will prevent a person

protection device provides 15×115 (1,725 watts); each

from replacing the 15-ampere fuse with a 20- or

circuit is enough for 1,725 divided by 3 (575 square feet).

30-ampere fuse, which may not blow out. If a

Note that 575 is a minimum figure; if future use is

circuit wired with 14-gauge wire (current capacity

considered, 500 or even 400 square feet per branch circuit

15 amperes) is fused with a 20- or 30-ampere fuse

should be used.

and an overload develops, more current than the

14-gauge wire is safely capable of carrying could

Special appliance circuits will provide electric power for

pass through the circuit. The result would be a

lighting, radio, TV, and small portable appliances.

heating of the wire and potential fire.

However, the larger electric appliances usually found in

the kitchen consume more power and must have their

•

Type-S fuses—Type-S fuses have different lengths

own special circuit.

and diameter threads for each amperage capacity.

An adapter is first inserted into the ordinary fuse

Section 220-3b of the code requires two special circuits to

holder, which adapts the fuse holder for only one

serve only appliance outlets in the kitchen, laundry,

capacity fuse. Once the adapter is inserted, it

pantry, family room, dining room, and breakfast room.

cannot be removed.

Both circuits must be extended to the kitchen; either one

or both of these circuits may serve the other rooms. No

•

Cartridge fuses—A cartridge fuse protects an

lighting outlets may be connected to these circuits, and

electric circuit in the same manner as an ordinary

they must be wired with 12-gauge wire and protected by

plug fuse, already described, protects an electric

a 20-ampere over-current device. Each circuit will have a

circuit. Cartridge fuses are often used as main fuses.

capacity of 20×115 (2,300 watts), which is not too much

when toasters often require more than 1,600 watts.

Electric Circuits

An electric circuit in good repair carries electricity

It is customary to provide a circuit for each of the

through two or three wires from the source of supply to

following appliances: range, water heater, washing

an outlet and back to the source. A branch circuit is an

machine, clothes dryer, garbage disposal, dishwasher,

furnace, water pump, air conditioner, heat pump, and air

compressor. These circuits may be either 115 volts or

230 volts, depending on the particular appliance or motor

installed.

Outlet Switches and Junction Boxes

The code requires that every switch, outlet, and joint in

wire or cable be housed in a box. Every fixture must be

mounted on a box. Most boxes are made of plastic or

metal with a galvanized coating. When a cable of any

style is used for wiring, the code requires that it be

securely anchored with a connector to each box it enters.

Grounding Outlets

An electrical appliance may appear to be in good repair,

and yet it might be a danger to the user. Older portable

Figure 11.18. Types of Fuses

Healthy Housing Reference Manual

11-13

electric drills consist of an electric motor inside a metal

grounded. If a two-opening outlet is grounded, it may be

casing. When the switch is depressed, the current flows to

adapted for use by a three-wire appliance by using an

the motor and the drill rotates. As a result of wear,

adapter. The loose-wire portion or screw tab of the

however, the insulation on the wire inside the drill may

adapter should be secured behind the metal screw of the

deteriorate and allow the hot side of the power cord to

outlet plate cover. Many appliances, such as electric

come in contact with the metal casing. This will not

shavers and some new hand tools, are double insulated

affect the operation of the drill.

and are safe without having a third ground wire.

A person fully clothed using the drill in the living room,

Polarized Plugs and Connectors

which has a dry floor, will not receive a shock, even

Plugs are polarized or unpolarized. Polarization helps

though he or she is in contact with the electrified drill

reduce the potential for shock. Consumers can easily

case. The operator’s body is not grounded because of the

identify polarized plugs; one blade-the ground prong-is

dry floor. If standing on a wet basement floor, the

wider than the other. Three-conductor plugs are

operator’s body might be grounded; and, when the

automatically polarized because they can only be inserted

electrified drill case is touched, current will pass through

one way. Polarized plugs are used to connect the most-

the operator’s body.

exposed part of an appliance to the ground wire so that if

you are touching a ground (such as a pipe, bathtub, or

To protect people from electrocution, the drill case is

faucet) and the exposed part of an appliance (the case, the

usually connected to the system ground by means of a

threaded part of a light bulb socket, etc.), you will not get

wire called an appliance ground. In this instance, as the

an electrical shock. Many appliances, such as electric

drill is plugged in, current will flow between the shorted

drills, are doubly insulated so the probability of any

hot wire and the drill case and cause the over-current

exposed part of the appliance being connected, by a short

device to break the circuit. Thus, the appliance ground

or other problem in the appliance, to either wire is very

has protected the human operator. Newer appliances and

small. Such devices often use unpolarized plugs where the

tools are equipped with two-prong polarized plugs, as

two prongs of the plug are identical.

discussed in the standards section of this manual.

Common Electrical Violations

The appliance ground (Figure 11.19) is the third wire

The most obvious things that a housing inspector must

found on many appliances. The appliance ground will be

check are the power supply; the type, location, and

of no use unless the outlet into which the appliance is

condition of the wiring; and the number and conditions of

plugged is grounded. Being in physical contact with a

wall outlets or ceiling fixtures required by the local code. In

ground outlet box grounds the outlet. Having a third

making an investigation, the following considerations will

ground wire, or a grounded conduit, as part of the circuit

serve as useful guides.

wiring grounds the outlet box.

All new buildings are required to have grounded outlets.

A two-lead circuit tester can be used to test the outlet.

The circuit tester lights when both of its leads are plugged

into the two elongated parallel openings of the outlet. In

addition, the tester lights when one lead is plugged into

the round third opening and the other is plugged into the

hot side of the outlet. Most problems can be resolved

using inexpensive testers resembling a plug with three

leads. These can be purchased in many stores and most

hardware stores for very reasonable prices.

If the conventional two-opening outlet is used, it may be

grounded if the screw that holds the outlet cover plate is

electrically connected to the third-wire ground. The tester

should light when one lead is in contact with a clean

paint-free metal outlet cover plate screw and the hot side

of the outlet. If the tester does not light, the outlet is not

Figure 11.19. Appliance Ground and Grounded Plug

11-14

Electricity

•

Power supply—Where is it, is it grounded

stairways in structures containing less than three

properly, and is it at least of the minimum

dwelling units may be supplied with conveniently

capacity required to supply current safely for

located light switches controlling an adequate

lighting and the major and minor appliances in

lighting system that may be turned on when

the dwelling?

needed, instead of full-time lighting.

•

Panel box covers or doors—These should be

•

Habitable room lighting—The standard here

accessible only from the front and should be

may be two floor convenience outlets (although

sealed in such a way that they can be operated

floor outlets are dangerous unless protected by

safely without the danger of contact with live or

proper dust and water covers) or one convenience

exposed parts of the wiring system.

outlet and one wall or ceiling electric light fixture.

This number is an absolute and often inadequate

•

Switch, outlets, and junction boxes—These also

minimum, given the contemporary widespread

must be covered to protect against danger of

use of electricity in the home. The minimum

electric shock.

should be the number required to provide

adequate lighting and power to accommodate

•

Frayed or bare wires—These are usually the result

lighting and appliances normally used in each room.

of long use and drying out and cracking of the

insulation, which leave the wires exposed, or of

•

Octopus outlets or wiring—This term is applied

constant friction and rough handling of the wire,

to outlets into which plugs have been inserted and

which cause it to fray or become bare. Wiring in

are being used to permit more than two lights or

this condition constitutes a safety hazard. Correction

portable appliances, such as a TV, lamp, or radio,

of such defects should be ordered immediately.

to be connected to the electrical system. The

condition occurs where the number of outlets is

•

Electric cords under rugs or other floor

insufficient to accommodate the normal use of

coverings—Putting electric cords in locations

the room. This practice overloads the circuit and

such as these is prohibited because of the potential

is a potential source of fire.

fire hazard caused by continuing contact over a

period of time between these heat-bearing cords

•

Outlet covers—Every outlet and receptacle must

and the flammable floor coverings. Direct the

be covered by a protective plate to prevent contact

occupant to shift the cords to a safe location, explain

of its wiring or terminals with the body,

why, and make sure it is done before you leave.

combustible objects, or water.

•

Ground fault circuit interrupter—All bathroom,

Following are six situations that can cause danger and

kitchen, and workroom outlets-where shock

should also be corrected.

hazard is great-should have GFCI outlets. Check

for lack of or nonuse of GFCI outlets.

Excessive or Faulty Fusing

The wire’s capacity must not be exceeded by the fuse or

•

Bathroom lighting—Bathrooms should include at

circuit breaker capacity or be left unprotected by faulty

least one permanently installed ceiling or wall

fusing or circuit breakers. Fuses and circuit breakers are

light fixture with a wall switch and plate located

safety devices designed to “blow” to protect against

and maintained so that there is no danger of short

overloading the electrical system or one or more of its

circuiting from use of other bathroom facilities or

circuits. Pennies under fuses are there to bypass the fuse.

splashing water. Fixture or cover plates should be

These are illegal and must be removed. Overfusing is

insulated or grounded.

done for the same reason. The latter can be prevented by

installing modern fusestats, which prevent use of any fuse of a

•

Lighting of public hallways, stairways, landings,

higher amperage than can be handled by the circuit it serves.

and foyers—A common standard is sufficient

lighting to illuminate 10 foot-candles on every part

Cords Run Through Walls or Doorways and

of these areas at all times. Sufficient lighting

Hanging Cords or Wires

means that people can clearly see their feet on all

This makeshift installation often is the work of an

parts of the stairways and halls. Public halls and

unqualified handyman or do-it-yourself occupant. The

Healthy Housing Reference Manual

11-15

inspector should check the local electrical code to

not disassemble the fuse box, circuit breaker, or other

determine the policy regarding this type of installation.

devices. Decisions must be made on what you see. If in

doubt, consult your supervisor.

Temporary Wiring

Temporary wiring should not be allowed, with the

Note whether any fuse boxes, circuit breakers, or junction

exception of extension cords that go directly from

boxes are uncovered. Examine all wiring for frayed or bare

portable lights and electric fixtures to convenience outlets.

spots; improper splicing; or rotted, worn, or inadequate

insulation. Avoid all careless touching; when in

Excessively Long Extension Cords

doubt—DON’T! If you see bare wires, have the owner

City code standards often limit the length of loose cords

call an electrician. Look for wires or cords in use in the

or extension lines to a maximum of 8 feet. This is

basement. Be certain all switch boxes and outlets are in a

necessary because cords that are too long will overheat if

tight, sound condition. Make sure that the emergency

overloaded or if a short circuit develops and, thus, create a

switch for an oil burner is at the top of the basement

fire hazard. This requirement does not apply to specially

stairs, not on top of the unit.

designed extension cords for operating portable tools and

trouble lights.

Bathrooms, kitchens, and utility rooms-where electric

shock hazard is great-should have GFCI outlets.

Dead or Dummy Outlets

These are sometimes installed to deceive the housing

While inspecting the bathroom, also check for dangerous

inspector. All outlets must be tested or the occupants

items, such as radios that are not made for bathroom use

questioned to see if these are live and functioning

or portable electric heaters. Have inappropriate items

properly. A dead outlet cannot be counted to determine

removed immediately. Such items have killed thousands

compliance with the code.

of people who touched them after getting out of the

bathtub or shower while still wet or because the appliance

Aluminum Wiring Inside the Home

fell into water the person had contact with.

Although aluminum is an excellent conductor, it tends to

oxidize on the conducting surface. The nonconductive

Electric washer and dryer combinations should have a

oxidized face of the conductor will arc from the remaining

240-volt circuit, 30-ampere service connected to a

conductive surfaces, and this arc can result in fire.

separate fuse or circuit breaker. Washer and dryer

combinations and other portable appliances should be

Inspection Steps

served by sufficiently heavy electrical service. If either of

The basic tools required by a housing inspector for

these special lines is not available under the above-stated

making an electrical inspection are fuse and circuit testers

conditions, consult your supervisor.

and a flashlight. The first thing to remember is that you

are in a strange house, and the layout is unfamiliar to

An electric range needs a 50-ampere, 240-volt circuit. A

you. The second thing to remember is that you are

dishwasher needs a 20-ampere, 120-volt circuit. A

dealing with electricity-take no chances. Go to the site of

separate three-wire circuit must be installed for an electric

the ground, usually at the water meter, and check the

water heater. Continue your inspection systematically

ground. It should connect to the water line on the street

through the house.

side of the water meter or be equipped with a jumper

wire. Do not touch any box or wire until you are sure of

To sum up, the housing inspector investigates specified

the ground. Go to the main fuse box or circuit breaker

electrical elements in a house to detect any obvious

box and check all fuses and breakers for operational

evidence of an insufficient power supply, to ensure the

integrity (proper amperage range; functional). Note the

availability of adequate and safe lighting and electrical

condition of the wiring and of the box itself and check

facilities, and to discover and correct any obvious hazard.

whether it is over-fused. Examine all wiring in the

Because electricity is a technical, complicated field, the

basement. Make sure you are standing in a dry spot

housing inspector, when in doubt, should consult his or

(concrete poses a particular problem because you cannot

her supervisor. The inspector cannot, however, close the

determine its water content from visual examination)

case until appropriate corrective action has been taken on

before touching any electrical device. Standing on a dry

all such referrals.

piece of wood is far safer than standing on concrete. Do

11-16

Electricity

References

comprehensive manual, from basic repairs to advanced

National Fire Protection Association. National

projects (Black & Decker Home Improvement Library;

electrical code handbook 2005. Florence, KY:

US edition). Chanhassen, MN: Creative Publishing

Thomson Delmar Learning; 2005.

International; 2001.

Center for Disease Control. Basic housing

Sunset Publishing. Basic wiring. 3rd edition. Menlo Park,

inspection. Atlanta: US Department of Health

CA: Sunset Books, 1995.

and Human Services; 1976.

Hometime.com. Electrical service panel: panel

British Columbia Safety Authority. The facts

components, circuit breakers, fuses, electrical glossary.

about aluminum wiring in the home. New

Hometime.com; no date. Available from URL:

Westminster, British Columbia, Canada: British

http://www.hometime.com/Howto/ projects/

Columbia Safety Authority; no date. Available

electric/elec_2.htm.

from URL: http://www.safetyauthority.ca/

services/esp/

Vandervort D. How your house works: electric systems.

The_Facts_About_Aluminum_Wiring_In_The_

Glendale, CA: Hometips.com; no date. Available from

Home.pdf.

URL: http://www.hometips.com/hyhw/

electrical/electric.html.

Consumer Product Safety Commission. May is

National Electrical Safety Month: good news for

PNM Resources. Residential subdivisions: electric service

homeowners-aluminum wiring fix still available.

requirements. In: Electric service guide. Albuquerque,

Washington, DC: Consumer Product Safety

NM: PNM; 2004. Available from URL:

Commission; 2003. Available from URL:

http://www.pnm.com/esg/chapters/56-63.pdf.

http://www.cpsc.gov/CPSCPUB/PREREL/prhtml

03/03120.html.

Textor K. Extension cord basics. Fine Homebuilding

2000, 129: 84-9. Available from URL:

Consumer Product Safety Commission. CPSC

http://www.taunton.com/finehomebuilding/

safety recommendations for aluminum wiring in

pages/h00010.asp.

homes. Washington, DC: Consumer Product

Safety Commission; 1974. Available from URL:

Consumer Product Safety Commission. Repairing

http://www.cpsc.gov/CPSCPUB/PREREL/prhtml

aluminum wiring. Washington, DC: Consumer Product

74/74040.html.

Safety Commission; 1994. CPSC #516. Available from

URL: http://www.cpsc.gov/CPSCPUB/PUBS/516.pdf.

AWG American wire gauge/diameter/resistance.

Cologne, Germany: Bernd Noack; no date.

Available from URL:

http://www.bnoack.com/data/wire-

resistance.html.

Consumer Product Safety Commission. Extension

cords fact sheet. Washington, DC: Consumer

Product Safety Commission; no date. CPSC #16.

Available from URL:

http://www.cpsc.gov/CPSCPUB/PUBS/16.html.

Additional Sources of Information

Croft T, Summers W. American electricians’ handbook.

14th edition, New York: McGraw-Hill Professional; 2002.

Tuck D, Tuck G, Woodson RD. Electrician’s instant

answers. New York: McGraw-Hill Professional; 2003.

Black and Decker. The complete guide to home wiring: a

Healthy Housing Reference Manual

11-17

Chapter 12: Heating, Air Conditioning, and Ventilating

“Our climate is warming at a faster rate than ever before recorded.”

“In many temperate countries, death rates during

the winter season are 10%-25% higher than those

D. James Baker

in the summer.” World Health Organization,

NOAA Administrator, 1993-2004

Health Evidence Network, November 1, 2004.

Introduction

This chapter provides a general overview of the heating

The quotes below provide a profound lesson in the need for

and cooling of today’s homes. Heating and cooling are

housing to provide protection from both the heat and cold.

not merely a matter of comfort, but of survival. Both

very cold and very hot temperatures can threaten health.

“France heat wave death toll set at 14,802: The

Excessive exposure to heat is referred to as heat stress and

death toll in France from August’s blistering heat

excessive exposure to cold is referred to as cold stress.

wave has reached nearly 15,000, according to a

government-commissioned report released

In a very hot environment, the most serious health risk is

Thursday, surpassing a prior tally by more than

heat stroke. Heat stroke requires immediate medical

3,000.” USA Today, September 25, 2003.

attention and can be fatal or leave permanent damage.

Heat stroke fatalities occur every summer. Heat

“In the study of the 1995 Chicago heat wave, those

exhaustion and fainting are less serious types of illnesses.

at greatest risk of dying from the heat were people

Typically they are not fatal, but they do interfere with a

with medical illnesses who were socially isolated

person’s ability to work.

and did not have access to air conditioning.”

Centers for Disease Control and Prevention,

At very cold temperatures, the most serious concern is

Morbidity and Mortality Weekly Report, July 4, 2003.

the risk for hypothermia or dangerous overcooling of the

body. Another serious effect of cold exposure is frostbite

“3 Deaths tied to cold . . .The bitter cold that

or freezing of exposed extremities, such as fingers, toes,

gripped the Northeast through the weekend and

nose, and ear lobes. Hypothermia can be fatal if

iced over roads was blamed for at least three deaths,

immediate medical attention is not received.

including that of a Philadelphia man found inside a

home without heat.” Lexington [Kentucky] Herald

Heat and cold are dangerous because the victims of heat

Leader, January 12, 2004.

stroke and hypothermia often do not notice the

Definitions of Terms Related to HVAC Systems

Air duct—A formed conduit that carries warm or cold air from the furnace or air-conditioner and back again.

Antiflooding Control—A safety control that shuts off fuel and ignition when excessive fuel oil accumulates in the

appliance.

Appliance:

High heat—A unit that operates with flue entrance temperature of combustion products above 1,500°F (820°C).

Medium heat—Same as high-heat, except above 600°F (320°C).

Low heat—same as high-heat, except below 600°F (320°C).

Boiler:

High pressure—A boiler furnishing pressure at 15 psi or more.

Low pressure (hot water or steam)—A boiler furnishing steam at a pressure less than 15 psi or hot water

not more than 30 psi.

Burner—A device that mixes fuel, air, and ignition in a combustion chamber.

Healthy Housing Reference Manual

12-1

symptoms. This means that family, neighbors, and

removed from the heat, cooled, and heavily hydrated.

friends are essential for early recognition of the onset of

Heat stroke signs and symptoms include sudden and

the conditions. The affected individual’s survival depends

severe fatigue, nausea, dizziness, rapid pulse,

on others to identify symptoms and to seek medical help.

lightheadedness, confusion, unconsciousness, extremely

Family, neighbors, and friends must be particularly

high temperature, and hot and dry skin surface. An

diligent during heat or cold waves to check on

individual who appears disorientated or confused, seems

individuals who live alone.

euphoric or unaccountably irritable, or suffers from

malaise or flulike symptoms should be moved to a cool

Although symptoms vary from person to person, the

location and medical advice should be sought

warning signs of heat exhaustion include confusion and

immediately.

profuse and prolonged sweating. The person should be

Definitions of Terms Related to HVAC Systems

Carbon monoxide (CO) detector—A device used to detect CO (specific gravity of 0.97 vs. 1.00 for oxygen, a colorless

odorless gas resulting from combustion of fuel). CO detectors should be placed on each floor of the structure at eye level

and should have an audible alarm and, when possible, a digital readout at eye level.

Chimney—A vertical shaft containing one or more passageways.

Factory-built chimney—A tested and accredited flue for venting gas appliances, incinerators and solid or liquid

fuel-burning appliances.

Masonry chimney—A field-constructed chimney built of masonry and lined with terra cotta flue or firebrick.

Metal chimney—A field-constructed chimney of metal.

Chimney connector—A pipe or breeching that connects the heating appliance to the chimney.

Clearance—The distance separating the appliance, chimney connector, plenum, and flue from the nearest surface of

combustible material.

Central cooling system—An electric or gas-powered system containing an outside compressor, cooling coils, and a

ducting system inside the structure designed to supply cool air uniformly throughout the structure.

Central heating system—A flue connected boiler or furnace installed as an integral part of the structure and designed to

supply heat adequately for the structure.

Collectors—The key component of active solar systems and are designed to meet the specific temperature requirements

and climate conditions for different end uses. Several types of solar collectors exist: flat-plate collectors, evacuated-tube

collectors, concentrating collectors, and transpired air collectors.

Controls:

High-low limit control—An automatic control that responds to liquid level changes and will shut down if they

are exceeded.

Primary safety control—The automatic safety control intended to prevent abnormal discharge of fuel at the burner

in case of ignition failure or flame failure.

Combustion safety control—A primary safety control that responds to flame properties, sensing the presence

of flame and causing fuel to be shut off in event of flame failure.

Convector—A radiator that supplies a maximum amount of heat by convection, using many closely spaced metal fins

fitted onto pipes that carry hot water or steam and thereby heat the circulating air.

Conversion—A boiler or furnace, flue connected, originally designed for solid fuel but converted for liquid or gas fuel.

Damper—A valve for regulating draft on coal-fired equipment. Generally located on the exhaust side of the combustion

chamber, usually in the chimney connector. Dampers are not allowed on oil- and gas-fired equipment.

Draft hood—-A device placed in and made a part of the vent connector (chimney connector or smoke pipe) from an

appliance, or in the appliance itself. The hood is designed to a) ensure the ready escape of the products of combustion in

the event of no draft, back draft, or stoppage beyond the draft hood; b) prevent backdraft from entering the appliance;

and c) neutralize the effect of stack action of the chimney flue upon appliance operation.

12-2

Heating, Air Conditioning, and Ventilating

Warning signs of hypothermia include nausea, fatigue,

heat, cool air, and ventilation, and helps control dust and

dizziness, irritability, or euphoria. Individuals also

moisture, which can lead to adverse health effects. The

experience pain in their extremities (e.g., hands, feet,

variables to be controlled are temperature, air quality, air

ears) and severe shivering. People who exhibit these

motion, and relative humidity. Temperature must be

symptoms, particularly the elderly and young, should be

maintained uniformly throughout the heated/cooled

moved to a heated shelter and medical advice should be

area. There is a 6°F to 10°F (-14°C to -12°C) variation

sought when appropriate.

in room temperature from floor to ceiling. The adequacy

of the HVAC system and the air-tightness of the

The function of a heating, ventilation, and air

structure or room determine the degree of personal safety

conditioning (HVAC) system is to provide for more than

and comfort within the dwelling.

human health and comfort. The HVAC system produces

Definitions of Terms Related to HVAC Systems

Draft regulator—A device that functions to maintain a desired draft in oil-fired appliances by automatically reducing the

chimney draft to the desired value. Sometimes this device is referred to in the field as air-balance, air-stat, or flue velocity

control or barometer damper.

Fuel oil—A liquid mixture or compound derived from petroleum that does not emit flammable vapor below a

temperature of 125°F (52°C).

Heat—The warming of a building, apartment, or room by a furnace or electrical stove.

Heating plant—The furnace, boiler, or the other heating devices used to generate steam, hot water, or hot air, which

then is circulated through a distribution system. It typically uses coal, gas, oil or wood as its source of heat.

Limit control—A thermostatic device installed in the duct system to shut off the supply of heat at a predetermined

temperature of the circulated air.

Oil burner—A device for burning oil in heating appliances such as boilers, furnaces, water heaters, and ranges. A burner

of this type may be a pressure-atomizing gun type, a horizontal or vertical rotary type, or a mechanical or natural draft-

vaporizing type.

Oil stove—A flue-connected, self-contained, self-supporting oil-burning range or room heater equipped with an integral

tank not exceeding 10 gallons; it may be designed to be connected to a separate oil tank.

Plenum chamber—An air compartment to which one or more distributing air ducts are connected.

Pump, automatic oil—A device that automatically pumps oil from the supply tank and delivers it in specific quantities

to an oil-burning appliance. The pump or device is designed to stop pumping automatically if the oil supply line breaks.

Radiant heat—A method of heating a building by means of electric coils, hot water, or steam pipes installed in the

floors, walls, or ceilings.

room. It may or may not be arranged to permit closing the grille.

Room heater—A self-contained, freestanding heating appliance (space heater) intended for installation in the space

being heated and not intended for duct connection.

Smoke detector—A device installed in several rooms of the structure to warn of the presence of smoke. It should provide

an audible alarm. It can be battery powered or electric, or both. If the unit is battery powered, the batteries should be

tested or checked on a routine basis and changed once per year. If the unit is equipped with a 10-year battery, it is not

necessary to replace the battery every year.

Tank—A separate tank connected, directly or by pump, to an oil-burning appliance.

Thimble—A metal or terra cotta lining for a chimney or furnace pipe.

Valve (main shut-off valve)—A manually operated valve in an oil line used to turn the oil supply to the burner on or off.

Vent system—The gas vent or chimney and vent connector, if used, assembled to form a continuous, unobstructed

passageway from the gas appliance to the outside atmosphere to remove vent gases.

Healthy Housing Reference Manual

12-3

Gas, electricity, oil, coal, wood, and solar energy are the

• Manufactured gas—This gas, as distributed, is

main energy sources for home heating and cooling. Heating

usually a combination of certain proportions of

systems commonly used are steam, hot water and hot air.

gases produced from coke, coal, and petroleum.

A housing inspector should have knowledge of the various

Its BTU value per cubic foot is generally closely

heating fuels and systems to be able to determine their

regulated, and costs are determined on a guaranteed

adequacy and safety in operation. To cover fully all

BTU basis, usually 520 to 540 BTUs per cubic foot.

aspects of the heating and cooling system, the entire area

and physical components of the system must be considered.

• Liquefied petroleum gas—Principal products of

liquefied petroleum gas are butane and propane.

Heating

Butane and propane are derived from natural gas

Fifty-one percent of the homes in the United States are

or petroleum refinery gas and are chemically

heated with natural gas, 30% are heated with electricity,

classified as hydrocarbon gases. Specifically,

and 9% with fuel oil. The remaining 11% are heated with

butane and propane are on the borderline

bottled fuel, wood, coal, solar, geothermal, wind, or solar

between a liquid and a gaseous state. At ordinary

energy [1]. Any home using combustion as a source of

atmospheric pressure, butane is a gas above 33°F

heating, cooling, or cooking or that has an attached

(0.6°C) and propane a gas at -42°F (-41°C).

garage should have appropriately located and maintained

These gases are mixed to produce commercial gas

carbon monoxide (CO) gas detectors. According to the

suitable for various climatic conditions. Butane

U.S. Consumer Product Safety Commission (CPSC),

and propane are heavier than air. The heat content of

from data collected in 2000, CO kills 200 people and

butane is 3,274 BTUs per cubic foot, whereas that

sends more than 10,000 to the hospital each year.

of propane is 2,519 BTUs per cubic foot.

The standard fuels for heating are discussed below.

Gas burners should be equipped with an automatic

shutoff in case the flame fails. Shutoff valves should be

Standard Fuels

located within 1 foot of the burner connection and on the

Gas

output side of the meter.

More than 50% of American homes use gas fuel. Gas

fuels are colorless gases. Some have a characteristic pungent

Caution: Liquefied petroleum gas is heavier than air;

odor; others are odorless and cannot be detected by smell.

therefore, the gas will accumulate at the bottom of

Although gas fuels are easily handled in heating equipment,

confined areas. If a leak develops, care should be taken to

their presence in air in appreciable quantities becomes a

ventilate the appliance before lighting it.

serious health hazard. Gases diffuse readily in the air,

making explosive mixtures possible. A proportion of

Electricity

combustible gas and air that is ignited burns with such a

Electricity has gained popularity for heating in many

high velocity that an explosive force is created. Because of

regions, particularly where costs are competitive with

these characteristics of gas fuels, precautions must be

other sources of heat energy, with usage increasing from

taken to prevent leaks, and care must be exercised when

2% in 1960 to 30% in 2000. With an electric system, the

gas-fired equipment is lit.

housing inspector should rely mainly on the electrical

inspector to determine proper installation. There are a few

Gas is broadly classified as natural or manufactured.

items, however, to be concerned with to ensure safe use of

the equipment. Check to see that the units are approved

• Natural gas—This gas is a mixture of several

by an accredited testing agency and installed according to

combustible and inert gases. It is one of the richest

the manufacturer’s specifications. Most convector-type

gases and is obtained from wells ordinarily located

units must be installed at least 2 inches above the floor

in petroleum-producing areas. The heat content

level, not only to ensure that proper convection currents

may vary from 700 to 1,300 British thermal units

are established through the unit, but also to allow

(BTUs) per cubic foot, with a generally accepted

sufficient air insulation from any combustible flooring

average figure of 1,000 BTUs per cubic foot.

material. The housing inspector should check for curtains

Natural gases are distributed through pipelines to the

that extend too close to the unit or loose, long-pile rugs

point of use and are often mixed with manufactured

that are too close. A distance of 6 inches on the floor and

gas to maintain a guaranteed BTU content.

12 inches on the walls should separate rugs or curtains

from the appliance.

12-4

Heating, Air Conditioning, and Ventilating

Heat pumps are air conditioners that contain a valve that

• The refrigerant vapor then goes back to the

allows switching between air conditioner and heater.

reversing valve to be directed to the compressor to

When the valve is switched one way, the heat pump acts

start the refrigeration cycle all over again.

like an air conditioner; when it is switched the other way,

it reverses the flow of refrigerants and acts like a heater.

Heat pumps [3] are quite efficient in their use of energy.

Cold is the absence of energy or calories of heat. To cool

However, heat pumps often freeze up; that is, the coils in

something, the heat must be removed; to warm

the outside air collect ice. The heat pump has to melt this

something, energy or calories of heat must be provided.

ice periodically, so it switches itself back to air conditioner

Heat pumps do both.

mode to heat up the coils. To avoid pumping cold air into

the house in air conditioner mode, the heat pump also

A heat pump has a few additions beyond the typical air

uses electric strip heaters to heat the cold air that the air

conditioner: a reversing valve, two thermal expansion valves,

conditioner is pumping out. Once the ice is melted, the

and two bypass valves. The reversing valve allows the unit

heat pump switches back to heating mode and turns off

to provide both cooling and heating. Figure 12.1 shows a

the burners.

heat pump in cooling mode. The unit operates as follows:

Radiant heat warms objects directly with longwave

•

The compressor compacts the refrigerant vapor

electromagnetic energy. The heating panels diffuse heating

and pumps it to the reversing valve.

energy rays in a 160° arc, distributing warmth evenly. The

goal is to achieve no more than a 4°F (-16°C) difference

•

The reversing valve directs the compressed vapor

in temperature between floor level and ceiling level.

to flow to the outside heat exchanger (condenser),

When properly installed, radiant heat warms a room

where the refrigerant is cooled and condensed to a

sooner and at lower temperature settings than do other

liquid.

kinds of heat. Extreme care must be taken to protect

against fire hazards from objects in close proximity to the

•

The air blowing through the condenser coil

infrared radiation reflectors. Inspectors dealing with this

removes heat from the refrigerant.

heat source should have specialized training. Radiant

heating is plastered into the ceiling or wall in some homes

•

The liquid refrigerant bypasses the first thermal

or in the brick or ceramic floors of bathrooms. If wires are

expansion valve and flows to the second thermal

bare in the plaster, they should be treated as open and

expansion valve at the inside heat exchanger

exposed wiring. The inspector should be knowledgeable

(evaporator) where it expands into the evaporator

about these systems, which are technical and relatively new.

and becomes vapor.

Fuel Oil

•

The refrigerant picks up heat energy from the air

Fuel oils are derived from petroleum, which consists

blowing across the evaporator coil and cool air

primarily of compounds of hydrogen and carbon

comes out at the other side of the coil. The cool

(hydrocarbons) and smaller amounts of nitrogen and

air is ducted to the occupied space as air-

sulfur. Domestic fuel oils are controlled by rigid

conditioned air.

specifications. Six grades of fuel oil—numbered 1

through 6—are generally used in heating systems; the

lighter two grades are used primarily for domestic heating:

• Grade Number 1—a volatile, distillate oil for use

in burners that prepare fuel for burning solely by

vaporization (oil-fired space heaters).

• Grade Number 2—a moderate weight, volatile,

distillate oil used for burners that prepare oil for

burning by a combination of vaporization and

atomization. This grade of oil is commonly used

in domestic heating furnaces.

Figure 12.1. Heat Pump in Cooling Mode [2]

Healthy Housing Reference Manual

12-5

Heating values of oil vary from approximately 152,000 BTU

emergency spill and overfill tanks [8]. A review of local

per gallon for number 6 oil to 136,000 BTU per gallon for

and state regulations should be completed before

number 1 oil. Oil is more widely used today than coal

installing underground tanks because many jurisdictions

and provides a more automatic source of heat and

do not allow burial of gas or oil tanks.

comfort. It also requires more complicated systems and

controls. If the oil supply is in the basement or cellar area,

Coal

certain code regulations must be followed (Figure 12.2)

The four types of coal are anthracite, bituminous, sub-

[4-7]. No more than two 275-gallon tanks may be

bituminous, and lignite. Coal is prepared in many sizes

installed above ground in the lowest story of any one

and combinations of sizes. The combustible portions of

building. The IRC recommends a maximum fuel oil

the coal are fixed carbons, volatile matter (hydrocarbons),

storage of 660 gallons. The tank shall not be closer than

and small amounts of sulfur. In combination with these

7 feet horizontally to any boiler, furnace, stove, or

are noncombustible elements composed of moisture and

exposed flame(s).

impurities that form ash. The various types differ in heat

content. Heat content is determined by analysis and is

Fuel oil lines should be embedded in a concrete or

expressed in British thermal units per pound.

cement floor or protected against damage if they run

across the floor. Each tank must have a shutoff valve that

Improper coal furnace operation can result in an

will stop the flow if a leak develops in the line to or in the

extremely hazardous and unhealthy home. Ventilation of

burner itself. A leak-tight liner or pan should be installed

the area surrounding the furnace is very important to

under tanks and lines located above the floor. They

prevent heat buildup and to supply air for combustion.

contain potential leaks so the oil does not spread over the

floor, creating a fire hazard.

Solar Energy

Solar energy has gained popularity in the last 25 years as

The tank or tanks must be vented to the outside, and a

the cost of installation of solar panels and battery storage

gauge showing the quantity of oil in the tank or tanks

has decreased. Improved technology with panels,

must be tight and operative. Steel tanks constructed

installation of panels, piping, and batteries has created a

before 1985 had a life expectancy of 12-20 years. Tanks

much larger market. Solar energy largely has been used to

must be off the floor and on a stable base to prevent

heat water. Today, there are more than a million solar

settlement or movement that may rupture the

water-heating systems in the United States. Solar water

connections. Figure 12.3 shows a buried outside tank

heaters use direct sun to heat either water or a heat-

installation. In 1985, federal legislation was passed

transfer fluid in collectors [3]. That water is then stored

requiring that the exterior components of underground

for use as needed, with a conventional system providing

storage tanks (USTs) installed after 1985 resist the effects

any necessary additional heating. A typical system will

of pressure, vibration, and movement. Federal regulations

reduce the need for conventional water heating by about

for USTs exclude the following: farm and residential tanks

two-thirds, minimizing the cost of electricity or the use of

of 1,100 gallons (420 liters) or less capacity; tanks storing

fossil fuel and thus the environmental impact associated

heating oil used on the premises; tanks on or above the

floor of basements; septic tanks; flow-through process

tanks; all tanks with capacity of 110 gallons or less; and

Figure 12.2. Piping Hookup for Inside Tank Installation [4]

Figure 12.3. Piping Hookup for Buried Outside Tank [4]

12-6

Heating, Air Conditioning, and Ventilating

with their use. The U.S. Department of Housing and

handled with care (breathing protection and protective

Urban Development and the U.S. Department of Energy

clothing) and care must be taken to prevent or contain

(DOE) have instituted initiatives to deploy new solar

release into the air [10].

technologies in the next generation of American housing

[3]. For example, DOE has the Million Solar Roofs

The furnace or boiler makes it difficult to supply air and

Initiative begun in 1997 to install solar energy systems in

ventilation for the room. Where codes and local authority

more than 1 million U.S. buildings by 2010.

permit, it may be more practical to place the furnace or

boiler in an open area. The ceiling above the furnace

Central Heating Units

should be protected to a distance of 3 feet beyond all

The boiler should be placed in a separate room whenever

furnace or boiler appurtenances, and this area should be

possible, which is usually required in new construction.

free of all storage material. The furnace or boiler should

In most housing inspections, however, the inspector is

be on a firm foundation of concrete if located in the cellar

dealing with existing conditions and must adapt the

or basement. If codes permit furnace installations on the

situation as closely as possible to acceptable safety

first floor, then they must be consulted for proper setting

standards. In many old buildings, the furnace is located in

and location.

the center of the cellar or basement. This location does

not lend itself to practical conversion to a boiler room.

Heating Boilers

The term boiler is applied to the single heat source that

Consider the physical requirements for a boiler or

can supply either steam or hot water (a boiler is often

furnace.

called a heater).

• Ventilation—More circulating air is required for

the boiler room than for a habitable room, to

reduce the heat buildup caused by the boiler or

furnace and to supply oxygen for combustion.

• Fire protection rating—As specified by various

codes (fire code, building code, and insurance

underwriters), the fire regulations must be strictly

adhered to in areas surrounding the boiler or

furnace. This minimum clearance for a boiler or

furnace from a wall or ceiling is shown in

Figures 12.4 and 12.5.

Asbestos was used in numerous places on furnaces to

Figure 12.5. Minimum Clearance for Steam or Hot Water Boiler and

protect buildings from fire and to prevent lost heat.

Mechanical Warm-air Furnace [4]

Figure 12.6 shows asbestos-coated heating ducts, for

example. Where asbestos insulation is found, it must be

Figure 12.4. Minimum Clearance for Pipeless Hot Air and Gravity Warm Air

Furnace [4]

Figure 12.6. Heating Ducts Covered With Asbestos Insulation

Healthy Housing Reference Manual

12-7

Boilers may be classified according to several kinds of

Fuel-burning Furnaces

characteristics. They are typically made from cast iron or

Some localities throughout the United States still use coal

steel. Their construction design may be sectional,

as a heating fuel, including residences, schools, colleges

portable, fire-tube, water-tube, or special. Domestic

and universities, small manufacturing facilities, and other

heating boilers are generally of low-pressure type with a

facilities located near coal sources.

maximum working pressure of 15 pounds per square inch

(psi) for steam and 30 psi for hot water. All boilers have a

In many older furnaces, the coal is stoked or fed into the

combustion chamber for burning fuel. Automatic fuel-

firebox by hand. The single-retort, underfeed-type

firing devices help supply the fuel and control the

bituminous coal stoker is the most commonly used

combustion. Hand firing is accomplished by the provision of

domestic automatic-stoking steam or hot-water boiler

a grate, ash pit, and controllable drafts to admit air under

(Figure 12.7). The stoker consists of a coal hopper, a

the fuel bed and over it through slots in the firing door. A

screw for conveying coal from hopper to retort, a fan that

check draft is required at the smoke pipe connection to

supplies air for combustion, a transmission for driving

control chimney draft. The gas passes from the

coal feed and fan, and an electric motor for supplying

combustion chamber to the flue passages (smoke pipe)

power. The air for combustion is admitted to the fuel

designed for maximum possible transfer of heat from the

through tuyeres (air inlets) at the top of the retort. The

gas. Provisions must be made for cleaning flue passages.

stoker feeds coal to the furnace intermittently in

accordance with temperature or pressure demands.

Cast-iron boilers are usually shipped in sections and

assembled at the site. They are generally classified as

Oil burners are broadly designated as distillate, domestic,

and commercial or industrial. Distillate burners are

• square or rectangular boilers with vertical

usually found in oil-fired space heaters. Domestic oil

sections; and

burners are usually power driven and are used in domestic

• round, square, or rectangular boilers with

heating plants. Commercial or industrial burners are used

horizontal pancake sections.

in larger central-heating plants for steam or power

generation.

Most steel boilers are assembled units with welded steel

construction and are called portable boilers. Large boilers

Domestic oil burners vaporize and atomize the oil and

are installed in refractory brick settings on the site. Above

deliver a predetermined quantity of oil and air to the

the combustion chamber, a group of tubes is suspended,

combustion chambers. Domestic oil burners operate

usually horizontally, between two headers. If flue gases

automatically to maintain a desired temperature.

pass through the tubes and water surrounds them, the

boiler is designated as the fire-tube type. When water

Gun-type burners atomize the oil either by oil pressure or

flows through the tubes, it is termed water-tube. Fire-tube

by low-pressure air forced through a nozzle. The oil

is the predominant type.

system pressure-atomizing burner consists of a strainer,

pump, pressure-regulating valve, shutoff valve and

Heating Furnaces

atomizing nozzle. The air system consists of a power-

Heating furnaces are the heat sources used when air is the

driven fan and an air tube that surrounds the nozzle and

heat-carrying medium. When air circulates because of the

electrode assembly.

different densities of the heated and cooled air, the

furnace is a gravity type. A fan may be included for the

air circulation; this type is called a mechanical warm-air

furnace. Furnaces may be of cast iron or steel and burn

various types of fuel.

Some new furnaces are as fuel efficient as 95%. Furnaces

with an efficiency of 90% or greater use two heat

exchangers instead of one. Energy savings come not only

from the increased efficiency, but also from improved

comfort at lower thermostat settings.

Figure 12.7. Typical Underfeed Coal Stoker Installation in Small Boilers [4]

12-8

Heating, Air Conditioning, and Ventilating

The fan and oil pump are generally connected directly to the

•

Electric—A high-voltage electric spark in the path

motor. Oil pressures normally used are about 100 psi, but

of an oil and air mixture causes ignition. This

pressures considerably in excess of this are sometimes used.

electric spark may be continuous or may operate

only long enough to ignite the oil. Electric

The form and parts of low-pressure, air-atomizing burners

ignition is almost universally used. Electrodes are

are similar to high-pressure atomizing (gun) burners

located near the nozzles, but not in the path of

(Figure 12.8) except for addition of a small air pump and

the oil spray.

a different way of delivering air and oil to the nozzle or orifice.

•

Gas pilot—A small gas pilot light that burns

The atomizing type burner, sometimes known as a

continuously is frequently used. Gas pilots usually

radiant or suspended flame burner, atomizes oil by

have expanded gas valves that automatically

throwing it from the circumference of a rapidly rotating

increase flame size when a motor circuit starts.

motor-driven cup. The burner is installed so that the

After a fixed interval, the flame reverts to normal

driving parts are protected from the heat of the flame by a

size (Figure 12.9).

hearth of refractory material at about the grate elevation.

Oil is fed by pump or gravity; the draft is mechanical or a

•

Electric gas—An electric spark ignites a gas jet,

combination of natural and mechanical.

which in turn ignites the oil-air mixture.

Horizontal rotary burners were originally designed for

•

Oil pilot—A small oil flame is used.

commercial and industrial use but are available in sizes

suitable for domestic use. In this burner, fuel oil being

•

Manual—A burning wick or torch is placed in

thrown in a conical spray from a rapidly rotating cup is

the combustion space through peepholes and thus

atomized. Horizontal rotary burners use electric gas or

ignites the charge. The operator should stand to

gas-pilot ignition and operate with a wide range of fuels,

one side of the fire door to guard against injury

primarily Numbers 1 and 2 fuel oil. Primary safety

from chance explosion.

controls for burner operation are necessary. An

antiflooding device must be a part of the system to stop

The refractory lining or material should be an insulating

oil flow if ignition in the burner should fail. Likewise, a

fireproof bricklike substance, never ordinary firebrick.

stack control is necessary to shut off the burner if the

The insulating brick should be set on end to build a

stack temperatures are exceeded, thus cutting off all power

2½-inch-thick wall from furnace to furnace. The size and

to the burner. This button must be reset before starting

shape of the refractory pot vary from furnace to furnace.

can be attempted. The newer models now use electric eye-

type control on the burner itself.

On the basis of the method used to ignite fuels, burners

are divided into five groups:

Figure 12.8. Cutaway View of Typical High-pressure Gun Burner [4]

Figure 12.9. Gas-fired Boiler

Source: HUD

Healthy Housing Reference Manual

12-9

The shape can be either round or square, whichever is

Water Heating Systems

more convenient to build. It is more important to use a

All water heating systems are similar in design and

special cement having properties similar to that of the

operating principle. The one-pipe gravity water heating

insulating refractory-type brick.

system is the most elementary of the gravity systems and

is shown in Figure 12.10. Water is heated at the lowest

Steam Heating Systems

point in the system. It rises through a single main because

Steam heating systems are classified according to the pipe

of a difference in density between hot and cold water. The

arrangement, accessories used, method of returning the

supply rise or radiator branch takes off from the top of

condensate to the boiler, method of expelling air from the

the main to supply water to the radiators. After the water

system, or the type of control used. The successful

gives up heat in the radiator, it goes back to the same

operation of a steam heating system consists of generating

main through return piping from the radiator. This cooler

steam in sufficient quantity to equalize building heat loss

return water mixes with water in the supply main and

at maximum efficiency, expelling entrapped air, and

causes the water to cool a little. As a result, the next

returning all condensate to the boiler rapidly. Steam

radiator on the system has a lower emission rate and must

cannot enter a space filled with air or water at pressure

be larger.

equal to the steam pressure. It is important, therefore, to

eliminate air and remove water from the distribution

Note in Figure 12.11 that the high points of the hot

system. All hot pipelines exposed to contact by residents

water system are vented and the low points are drained.

must be properly insulated or guarded. Steam heating

In this case, the radiators are the high points and the

systems use the following methods to return the

heater is the low point.

condensate to the boiler:

•

One-pipe forced-feed system—If a pump or

•

Gravity one-pipe air-vent system—One of the

circulator is introduced in the main near the heater

earliest types used, this method returns

of the one-pipe system, it becomes a forced

condensate to the boiler by gravity. This system is

system that can be used for much larger

generally found in one-building-type heating

applications than can the gravity type. This system

systems. The steam is supplied by the boiler and

can operate at higher water temperatures than the

carried through a single system or pipe to

gravity system can. When the water is moving

radiators, as shown in Figure 12.10. Return of the

faster and at higher temperatures, it makes a more

condensate is dependent on hydrostatic head.

responsive system, with smaller temperature drops

Therefore, the end of the stream main, where it

and smaller radiators for the same heating load.

attaches to the boiler, must be full of water

(termed a wet return) for a distance above the

•

Two-pipe gravity system—A one-pipe gravity

boiler line to create a pressure drop balance

system may become a two-pipe system if the return

between the boiler and the stream main.

radiator branch connects to a second main that

returns water to the heater (Figure 12.12). Water

Radiators are equipped with an inlet valve and an

temperature is practically the same in the entire

air valve. The air valve permits venting of air from

radiator.

the radiator and its displacement by steam.

Condensate is drained from the radiator through

the same pipe that supplies steam.

•

Two-pipe steam vapor system with return trap—

The two-pipe vapor system with boiler return trap

and air eliminator is an improvement of the one-

pipe system. The return connection of the radiator

has a thermostatic trap that permits flow of

condensate and air only from the radiator and

prevents steam from leaving the radiator. Because

the return main is at atmospheric pressure or less,

a boiler return trap is installed to equalize

condensate return pressure with boiler pressure.

Figure 12.10. Typical Gravity One-pipe Heating System [4]

12-10

Heating, Air Conditioning, and Ventilating

•

Two-pipe forced-circulation system—This system

• Heat distribution—The most common source of

is similar to a one-pipe forced-circulation system

trouble in these systems is insufficient pipe area,

except that it uses the same piping arrangement

usually in the return or cold air duct. The total

found in the two-pipe gravity system.

cross-section area of the cold duct or ducts must

be at least equal to the total cross-section area of

•

Expansion tanks—When water is heated, it tends

all warm ducts.

to expand. Therefore, an expansion tank is necessary

in a hot water system. The expansion tank, either

• Pipeless furnaces—The pipeless hot-air furnace is

open or closed, must be of sufficient size to

the simplest type of hot-air furnace and is suitable

permit a change in water volume within the

for small homes where all rooms can be grouped

heating system. If the expansion tank is open, it

about a single large register. Other pipeless gravity

must be placed at least 3 feet above the highest

furnaces are often installed at floor level. These are

point of the system. It will require a vent and an

really oversized jacketed space heaters. The most

overflow. The open tank is usually in an attic, where

common difficulty experienced with this type of

it needs protection from freezing.

furnace is supplying a return air opening of

sufficient size on the floor.

The closed expansion tank is found in modern

installations. An air cushion in the tank compresses

Forced-Warm-Air Heating Systems. The mechanical

and expands according to the change of volume

warm-air furnace is the most modern type of warm-air

and pressure in the system. Closed tanks are

equipment (Figures 12.13 and 12.14). It is the safest type

usually at the low point in the system and close to

because it operates at low temperatures. The principle of a

the heater. They can, however, be placed at almost

any location within the heating system.

Air Heating Systems

Gravity Warm-air Heating Systems. These operate

because of the difference in specific gravity of warm air

and cold air. Warm air is lighter than cold air and rises if

cold air is available to replace it (Figure 12.13).

• Operation—Satisfactory operation of a gravity

warm-air heating system depends on three factors:

size of warm air and cold air ducts, heat loss of

the building, and heat available from the furnace.

Figure 12.12. Two-pipe Gravity Water Heating System [4]

Figure 12.11. One-pipe Gravity Water Heating System [4]

Figure 12.13. Warm-air Convection Furnace [4]

Healthy Housing Reference Manual

12-11

forced-warm-air heating system is very similar to that of

instructions and warning labels to all members of

the gravity system, except that a fan or blower is added to

the household to be certain that everyone

increase air movement. Because of the assistance of the

understands how to operate the heater safely.

fan or blower, the pitch of the ducts or leaders can be

Keep the owner’s manual in a convenient place to

disregarded; therefore, it is practical to deliver heated air

refer to when needed.

in the most convenient places.

•

Choose a space heater that has been tested and

• Operation—In a forced-air system, operation of

certified by a nationally recognized testing

the fan or blower must be controlled by air

laboratory. These heaters meet specific safety

temperature in a bonnet or by a blower control

standards.

furnace stat. The blower control starts the fan or

blower when the temperature reaches a certain

•

Buy a heater that is the correct size for the area

point and turns the fan or blower off when the

you want to heat. The wrong size heater could

temperature drops to a predetermined point.

produce more pollutants and may not be an

efficient use of energy.

• Heat distribution—Dampers in the various

warm-air ducts control distribution of warm air

•

Choose models that have automatic safety

either at the branch takeoff or at the warm-air

switches that turn off the unit if it is tipped over

outlet. Humidifiers are often mounted in the

accidentally.

supply bonnet to regulate the humidity within the

residence.

•

Select a space heater with a guard around the

flame area or heating element. Place the heater on

Space Heaters

a level, hard, nonflammable surface, not on rugs

Space heaters are the least desirable type of heating from

or carpets or near bedding or drapes. Keep the

the viewpoint of fire safety and housing inspection. A

heater at least 3 feet from bedding, drapes,

space heater is a self-contained, free-standing air-heating

furniture, or other flammable materials.

appliance intended for installation in the space being

heated and not intended for duct connection. According

•

Keep doors open to the rest of the house if you

to the CPSC, consumers are not using care when

are using an unvented fuel-burning space heater.

purchasing and using space heaters. Approximately

This helps prevent pollutant build-up and

21,800 residential fires are caused by space heaters a year,

promotes proper combustion. Follow the

and 300 people die in these fires. An estimated 6,000

manufacturer’s instructions for oil heaters to

persons receive hospital emergency room care for burn

provide sufficient combustion air to prevent CO

injuries associated with contacting hot surfaces of space

production.

heaters, mostly in nonfire situations.

•

Never leave a space heater on when you go to

Individuals using space heaters should use the heaters in

sleep. Never place a space heater close to any

accordance with the following precautions:

sleeping person.

• Read and follow the manufacturer’s operating

•

Turn the space heater off if you leave the area.

instructions. A good practice is to read aloud the

Keep children and pets away from space heaters.

Children should not be permitted to either adjust

the controls or move the heater.

•

Keep any portable heater as least 3 feet away from

curtains, newspapers, or anything that might burn.

•

Have a smoke detector with fresh batteries on

each level of the house and a CO detector outside

the sleeping area. Install a CO monitor near oil

space heaters at the height recommended by the

Figure 12.14. Cross-sectional View of Building Showing Forced warm-air

manufacturer.

Heating System [4]

12-12

Heating, Air Conditioning, and Ventilating

• Be aware that mobile homes require specially

combustion. The upper part of the bowl has a flame ring

designed heating equipment. Only electric or

or collar. Figure 12.15 shows a perforated-sleeve burner.

vented fuel-fired heaters should be used.

When several space heaters are installed in a building, an

oil supply from an outside tank to all heaters is often

• Have gas and kerosene space heaters inspected

desirable. Figure 12.16 shows the condition of a burner

annually.

flame with different rates of fuel flow and indicates the

ideal flame height.

• Do not hang items to dry above or on the heater.

Electric Space Heaters

• Keep all heaters out of exit and high-traffic areas.

Electric space heaters do not need to be vented.

• Keep portable electric heaters away from sinks,

Gas-fired Space Heaters

tubs, and other wet or damp places to avoid

The three types of gas-fired space heaters (natural,

deadly electric shocks.

manufactured, and liquefied petroleum gas) have a similar

construction. All gas-fired space heaters must be vented to

• Never use or store flammable liquids (such as

prevent a dangerous buildup of poisonous gases. Each

gasoline) around a space heater. The flammable

unit console consists of an enamel steel cabinet with top

vapors can flow from one part of the room to

and bottom circulating grilles or openings, gas burners,

another and be ignited by the open flame or by an

heating elements, gas pilot, and a gas valve. The heating

electrical spark.

element or combustion chamber is usually cast iron.

Coal-fired Space Heaters (Cannon Stove)

Caution: All gas-fired space heaters and their connections

A coal stove is made entirely of cast iron. Coal on the

must be approved by the American Gas Association

grates receives primary air for combustion through the

(AGA). They must be installed in accordance with the

grates from the ash-door draft intake. Combustible gases

recommendations of that organization or the local code.

driven from the coal by heat burn in the barrel of the

stove, where they receive additional or secondary air

Venting

through the feed door. The side and top of the stove

Use of proper venting materials and correct installation of

absorb the heat of combustion and radiate it to the

venting for gas-fired space heaters is necessary to

surrounding space. Coal stoves must be vented to the flue.

minimize harmful effects of condensation and to ensure

that combustion products are carried off. (Approximately

Oil-fired Space Heaters

12 gallons of water are produced in the burning of

Oil-fired space heaters

have atmospheric

vaporizing-type

burners. The burners

require a light grade of

fuel oil that vaporizes

easily and in

comparatively low

temperatures. In

addition, the oil must

be such that it leaves

only a small amount of

carbon residue and ash

within the heater. Oil

stoves must be vented.

The burner of an oil-

Figure 12.15. Perforated-sleeve Burner

fired space heater

consists essentially of a bowl, 8 to 13 inches in diameter,

Figure 12.16. Condition of Burner Flame with Different Rates of Fuel Flow [4]

with perforations in the side that admit air for

Healthy Housing Reference Manual

12-13

1,000 cubic feet of natural gas. The inner surface of the

enough to penetrate the heat shielding and throw burning

vent must therefore be heated above the dew point of the

material onto the roof of the home.

combustion products to prevent water from forming in

the flue.) A horizontal vent must be given an upward

The vent should be run at least 3 feet above any

pitch of at least 1 inch per foot of horizontal distance.

projection within 20 feet of the building to place it above

a possible pressure zone due to wind currents (Figure 12.18).

When the smoke pipe extends through floors or walls, the

A weather cap should prevent entrance of rain and snow.

metal pipe must be insulated from the floor or wall

Gas-fired space heaters, as well as gas furnaces and water

system by an air space (Figure 12.17). Sharp bends should

heaters, must be equipped with a backdraft diverter

be avoided. A 9° vent elbow has a resistance to flow

(Figure 12.19) to protect heaters against downdrafts and

equivalent to that of a straight section of pipe with a

excessive updrafts. Only draft diverters approved by the AGA

length 10 times the elbow diameter. Be sure that vents are

should be used.

of rigid construction and resistant to corrosion by flue gas

products. Several types of venting material are available

The combustion chamber or firebox must be insulated

such as B-vent and other ceramic-type materials. A

from the floor, usually with airspace of 15 to 18 inches.

chimney lined with firebrick type of terra cotta must be

The firebox is sometimes insulated within the unit and

relined with an acceptable vent material if it is to be used

thus allows for lesser clearance firebox combustibles.

for venting gas-fired appliances.

Floors should be protected where coal space heaters are

The same size vent pipe should be used throughout its

located. The floor protection allows hot coals and ashes to

length. A vent should never be smaller than the heater

cool off if dropped while being removed from the ash

outlet except when two or more vents converge from

chamber. Noncombustible walls and materials should be

separate heaters. To determine the size of vents beyond

used when they are exposed to heated surfaces. For space

the point of convergence, one-half the area of each vent

heaters, a top or ceiling clearance of 36 inches, a wall

should be added to the area of the largest heater’s vent.

clearance of 18 inches, and a smoke pipe clearance of

Vents should be installed with male ends of inner liner

18 inches are recommended.

down to ensure condensate is kept within pipes on a cold

start. The vertical length of each vent or stack should be

Hydronic Systems

at least 2 feet greater than the length between horizontal

Hydronic (circulating water) systems involving traditional

connection and stack. Remember that the more

baseboards can be single-pipe or two-pipe. Radiant

conductive the unit, the lower the temperature of

systems are also an option. All hydronic systems require

combustion and the more byproducts of combustion are

an expansion tank to compensate for the increase in water

likely to be produced. These by-products are sometimes

volume when it is heated (i.e., the volume of 50°F [10°C]

referred to as soot and creosote. These by-products will

water increases almost 4% when it is heated to 200°F

build up in vents, stacks, and chimneys. They are extremely

[93°C]). Single-pipe hydronic systems are most

flammable and can result in fire in these units that is hot

commonly used in residences. They use a single pipe with

hot water flowing in a series loop from radiator to

radiator. Massachusetts has a prototype set of hydronic

systems requirements [11].

Figure 12.17. Wall and Ceiling Clearance Reduction [4]

Figure 12.18. Draft Relation to Height of Chimney [4]

12-14

Heating, Air Conditioning, and Ventilating

The drawback to this arrangement is that the temperature

penalty in the winter. However, increased outdoor noise

of the water decreases as it moves through each radiator.

levels, pollution, and security issues make relying on open

Thus, larger radiators are needed for those locations

windows a less attractive option in some locations today.

downstream in the loop. A common solution to this is

An air conditioning system of some kind may be installed

multiple loops or zones. Each zone has its own

in the home. It may be a window air conditioner or

temperature control with circulation provided by a small

through-the-wall unit for cooling one or two rooms, or a

pump or zone valve in each loop. Two-pipe hydronic

central split-system air conditioner or heat pump. In any

systems use a pipe for supplying hot water to the radiators

event, the performance of these systems, in terms of

and a second pipe for returning the water from the

providing adequate comfort without excessive energy use,

radiators to the boiler.

should be investigated. The age of the equipment alone

will provide some indication. If the existing system is

There are also direct- and reverse-return arrangements.

more than 10 years old, replacement should be considered

The direct-return system can be difficult to balance

because it is much less efficient than today’s systems and

because the pressure drop through the nearest radiator

nearing the end of its useful life.

piping can be significantly less than for the farthest

radiator. Reverse-return systems take care of the balancing

The refrigerant commonly used in today’s residential air

problem, but require the expense of additional piping.

conditioners is R-22. Because of the suspicion that R-22

Orifice plates at radiator inlets or balancing valves at

depletes the ozone layer, manufacturers will be prohibited

radiator outlets can also be used to balance the pressure

from producing units with R-22 in 2010. The leading

drops in a direct-return system.

replacements for R-22 are R-134A and R-410A, and new

products are now available with these nonozone-depleting

Direct Vent Wall Furnaces

refrigerants.

Direct vent wall furnaces are specifically designed for

areas where flues or chimneys are not available or cannot

The performance measure for electric air conditioners

be used. The furnace is directly vented to the outside and

with capacities less than 65,000 BTU is the seasonal

external air is used to support combustion. The air on the

energy efficiency ratio (SEER). SEER is a rating of

inside is warmed as it recirculates around a sealed chamber.

cooling performance based on representative residential

loads. It is reported in units of BTU of cooling per watt

Cooling

per hour of electric energy consumption. It includes

Air Conditioning

energy used by the unit’s compressor, fans, and controls.

Many old homes relied on passive cooling-opening windows

The higher the SEER, the more efficient the system.

and doors and using shading devices-during the summer

However, the highest SEER unit may not provide the

months. Homes were designed with windows on opposite

most comfort. In humid climates, some of the highest

walls to encourage cross ventilation and large shade trees

SEER units exhibit poor dehumidification capability

reduced solar heat gains. This approach is still viable, and

because they operate at higher evaporator temperatures to

improved thermal performance (insulating value)

attain the higher efficiency. A SEER of at least 10 is

windows are available that allow for larger window areas

required by the National Appliance Energy Conservation

to let in more air in the summer without the heat loss

Act of 1987 for conventional central split-system air-

cooled systems. The Department of Energy announced a

SEER of 13 effective January 2006.

Cooling system options vary widely, depending on the

level of control and comfort desired by the homeowner.

Fans can increase circulation and reduce cooling loads,

but they may be unsatisfactory in hot climates because

their cooling capability is directly limited by outdoor

conditions. Radiant barriers can reduce cooling loads in

very hot climates. Evaporative coolers can be a relatively

inexpensive and effective method of cooling in dry

climates, such as the Southwest. Electric air conditioning

maintains a comfortable indoor temperature and

Figure 12.19. Location and Operation of Typical Backdraft Diverter [4]

humidity even under the most severe outdoor conditions.

Healthy Housing Reference Manual

12-15

More than 75% of new homes in the United States are

Circulation Fans

equipped with some form of central air conditioning:

Air movement can make a person feel comfortable even

50% of the homes in the Northeast, 75% in the Midwest,

when dry-bulb temperatures are elevated. A circulation

95% in the South, and approximately 60% in the West.

fan (ceiling or portable) that creates an airspeed of 150 to

Electric air conditioning removes moisture from the air

200 feet per minute can compensate for a 4°F (-16°C)

and reduces its temperature. It can be a good investment

increase in temperature.

because, in most parts of the country, the payback is

significant when the house is sold.

Ceiling circulation fans also can be beneficial in the

heating season by redistributing warm air that collects

Electric air conditioners that use the vapor-compression,

along the ceiling, but they can be noisy.

refrigeration cycle are available in a variety of sizes and

configurations, ranging from small window units to large

Evaporation Coolers

central systems. The most common form of central air

In dry climates, as in the southwestern United States, an

conditioning is a split-system with a warm air furnace

evaporative cooler or “swamp” cooler may provide

(Figure 12.20). The same ductwork is used for distributing

sufficient cooling. This system cools an airstream by

conditioned air during the heating and cooling seasons.

evaporating water into it; the airstream’s relative humidity

Supply air is cooled and dehumidified as it passes over an

increases while the dry-bulb temperature decreases. A

A-shaped evaporator coil. The liquid refrigerant

95°F (35°C), 15% relative humidity airstream can be

evaporates inside the coil as it absorbs heat from the air.

conditioned to 75°F (24°C), 50% relative humidity. The

The refrigerant gas then travels through refrigerant piping

simplest direct systems are centrally located and use a

to the outdoor unit, where it is pressurized in an

pump to supply water to a saturated pad over which the

electrically driven compressor, raising its temperature and

supply air is blown. Indirect systems use a heat exchanger

pressure, and returned to a liquid state in the condenser

between the airstream that is cooled by evaporating water

as it releases, or dumps, the heat to the outdoors. A fan

and the supply airstream. The moisture level of the supply

draws outdoor air in over the condenser coil. The use of

airstream is not affected as it is cooled.

two-speed indoor fans can be advantageous in this type of

system because the cooling load often requires higher

Evaporation coolers have lower installation and operating

airflows than the heating load. The lower speed can be

costs than electric air conditioning. No ozone-depleting

used for the heating season and for improved

refrigerant is involved. They provide high levels of

dehumidification performance during the cooling season.

ventilation because they typically condition and supply

The condenser unit for a house air conditioner is shown

100% outside air.

in Figure 12.21.

The disadvantages are that bacterial contamination can

result if not properly maintained and they are only

appropriate for dry, hot climates.

Figure 12.20. Split-system Air Conditioner

Figure 12.21. External Air-conditioning Condenser Unit

12-16

Heating, Air Conditioning, and Ventilating

Safety

of the chimney above the roof either loses insulation or

Cooling homes with window air conditioners requires

the insulation peels back, it indicates potential poisonous

attention to the maintenance requirements of the unit.

gas release or water leakage problems and a need for

The filter must be cleaned or replaced as recommended

rebuilding. Exterior deterioration of the chimney, if

by the manufacturer, and the drip pan should be checked

neglected too long, will permit erosion from within the

to ensure that proper drainage from the unit is occurring.

flues and eventually block the flue opening.

The pans should be rinsed and disinfected as

Rusted flashing at the roof level will also contribute to the

recommended by the manufacturer. Both bacteria and

chimney’s deterioration. Efflorescence on the inside wall

fungi can establish themselves in these areas and present

of the chimney below the roof and on the outside of the

serious health hazards.

chimney, if exposed, will show salt accumulations—a

telltale sign of water penetration and flue gas escape and a

Condensation forms on the cooling coils of central air

sign of chimney deterioration. During rainy seasons, if

units inside and outside the home. These units should

terra cotta chimneys leak, dark areas show the number of

have a properly installed drip pan and should be drained

flues inside the masonry chimney so they can actually be

according to the manufacturer’s instructions. They also

counted. When this condition occurs, it usually requires

should receive routine maintenance, flushing, and

2 or 3 months to dry out. After drying out, the mortar

disinfection. In the spring, before starting the air

joints are discolored (brown). After a few years of this

conditioner, the unit should be checked by a professional

type of deterioration, the joints can be distinguished

or someone familiar with the operation of the system.

whether the chimney is wet or dry. These conditions

This is a good time to check drip line(s) for conditions

usually develop when coal is used and become more

such as plugs, cracks, or bacterial contamination because

pronounced 2 to 5 years after conversion to oil or gas.

many of these lines are plastic. The drip pan should be

cleaned thoroughly and disinfected if necessary or

An unlined chimney can be checked for deterioration

replaced. A plugged drip line can cause water damage by

below the roofline by looking for residue deposited at the

overflow from the drip pan. In the fall, the heat unit also

base of the chimney, usually accessible through a cleanout

should be checked before starting the system. Care should

(door or plug) or breaching. Red granular or fine powder

be taken with both window air conditioning units and

showing through coal or oil soot will generally indicate, if

central air systems to use quality air filters that are

in quantity (a handful), that deterioration is excessive and

designed for the specific units and meet the specifications

repairs are needed.

required by the system’s manufacturer.

Unlined chimneys with attached gas units will be devoid

The housing inspector should be on the alert for unvented,

of soot, but will usually show similar telltale brick powder

open flame heaters. Coil-type, wall-mounted water

and deterioration. Manufactured gas has a greater

heaters that do not have safety relief valves are not

tendency to dehydrate and decompose brick in chimney

permitted. Kerosene (portable) units for cooking or

flues than does natural gas. For gas installations in older

heating should be prohibited. Generally, open-flame

portable units are not allowed under fire safety regulations.

In oil heating units, other than integral tank units, the oil

must be filled and vented outside the building. Filling oil

within buildings is prohibited. Cutoff switches should be

close to the entry but outside of a boiler room.

Chimneys

Chimneys (Figure 12.22) are often an integral part of a

building. Masonry chimneys must be tight and sound;

flues should be terra cotta-lined; and, where no linings are

installed, the brick should be tight to permit proper draft

and elimination of combustion gases.

Chimneys that act as flues for gas-fired equipment must

Figure 12.22. Chimney Plan [4]

be lined with either B vent or terra cotta. When a portion

Healthy Housing Reference Manual

12-17

homes, utility companies usually specify chimney

Fireplace walls should be no less than 8 inches thick; if

requirements before installlation; therefore, older

built of stone or hollow masonry units, they should be no

chimneys may require the installation of terra cotta liners,

less than 12 inches thick. The faces of all walls exposed to

nonlead-lined copper liners, stainless steel liners, or transit

fire should be lined with firebrick or other suitable fire-

pipe. Black carbon deposits around the top of the

resistant material. When the lining consists of 4 inches of

chimney usually indicate an oil burner operation using a

firebrick, such lining thickness may be included in the

low air ratio and high oil consumption. Prolonged

required minimum thickness of the wall.

operation in this burner setting results in long carbon

water deposits down the chimney for 4 to 6 feet or more

The fireplace hearth should be constructed of brick,

and should indicate to the inspector a possibility of poor

stone, tile, or similar incombustible material and should

burner maintenance. This will accent the need to be more

be supported on a fireproof slab or on a brick arch. The

thorough on the next inspection. This type of condition

hearth should extend at least 20 inches beyond the

can result from other causes, such as improper chimney

chimney breast and no less than 12 inches beyond each side

height, or exterior obstructions, such as trees or buildings,

of the fireplace opening along the chimney breast. The

that will cause downdrafts or insufficient draft or

combined thickness of the hearth and its supporting

contribute to a faulty heating operation. Rust spots and soot-

construction should be no less than 6 inches at any point.

mold usually occur on deteriorated galvanized smoke pipe.

It is important that all wooden beams, joists, and studs

are set off from the fireplace and chimney so that there is

Fireplaces

no less than 2 inches of clearance between the wood

Careful attention should be given to construction of the

members and the sidewalls of the fireplace or chimney

fireplace (Figure 12.23). Improperly built fireplaces are a

and no less than 4 inches of clearance between wood

serious safety and fire hazard. The most common causes of

members and the back wall of the fireplace.

fireplace fires are thin walls, combustible materials such as

studding or trim against sides and back of the fireplace,

A gas-log set is primarily a decorative appliance. It

wood mantels, and unsafe hearths.

includes a grate holding ceramic logs, simulated embers, a

gas burner, and a variable flame controller. These sets can

be installed in most existing fireplaces. There are two

principal types: vented and unvented. Vented types

require a chimney flue for exhausting the gases. They are

only 20% to 30% efficient; and most codes require that

the flue be welded open, which results in an easy exit path

for heated room air. Unvented types operate like the

burner on a gas stove and the combustion products are

emitted into the room. They are more efficient because

no heat is lost up the flue and most are equipped with

oxygen-depletion sensors. However, unvented types are

banned in some states, including Massachusetts and

California. Gas fireplaces incorporate a gas-log set into a

complete firebox unit with a glass door. Some have built-

in dampers, smoke shelves, and heat-circulating features

that allow them to provide both radiant and convective

heat. Units can have push-button ignition, remote

control, variable heat controls, and thermostats. Gas

fireplaces are more efficient than gas logs, with efficiencies

of 60% to 80%. Many draw combustion air in from the

outside and are direct vented, eliminating the need for a

chimney. Some of these units are wall-furnace rated.

There are also electric fireplaces that provide the

ambience of a fire and, if desired, a small amount of

resistance heat. These units have no venting requirements.

The advantages are that there are no ashes or flying sparks

Figure 12.23. Fireplace Construction [4]

that occur with wood-burning fireplaces. They are not

12-18

Heating, Air Conditioning, and Ventilating

affected by wood-burning bans imposed in some areas

US Environmental Protection Agency. Overview

when air quality standards are not met. Direct-vented gas

of the federal underground storage tank program.

or electric models eliminate the need for a chimney.

Washington, DC: U.S. Environmental Protection

Agency; no date. Available from URL:

The disadvantages are that the cost for equipment and

http://www.epa.gov/swerust1/overview.htm.

running the gas line can be high.

US Department of Housing and Urban

References

Development. Initiatives Programs. Washington,

US Census Bureau. Rooms, number of bedrooms,

DC: US Department of Housing and Urban

and house heating fuel: 2000. Census 2000

Development; 2004. Available from URL:

Summary File 4 (SF4). Washington, DC: US

http://www.hud.gov/offices/cpd/energyenviron/

Census Bureau; 2000. Available from URL:

energy/initiatives.

http://factfinder.census.gov [select Data Sets, then

select Census 2000 Summary File 4 (SF 4) -

10. US Environmental Protection Agency. Sources of

Sample Data].

indoor air pollution—asbestos. Washington, DC:

U.S. Environmental Protection Agency; no date.

National Energy Efficiency Committee. Building:

Available from URL: http://www.epa.gov/

heat pumps; application of heat pumps in

iaq/asbestos.html.

Singapore. Singapore: National Environment

Agency; 2003. Available from URL:

11. The Commonwealth of Massachusetts Board of

http://www.neec.gov.sg/building/

Building Regulations and Standards (BBRS).

heat_pump.shtm.

Hydronic system requirements. Boston: The

Commonwealth of Massachusetts Board of

National Energy Efficiency Committee.

Building Regulations and Standards (BBRS); no

Renewables: solar energy. Singapore: National

date. Available from URL: http://www.mass.gov/

Environment Agency; no date. Available from

bbrs/commntry/cmpxhydr.htm.

URL: http://www.neec.gov.sg/

renewables/solar.shtm.

Additional Sources of Information

McQuiston FC, Parker JD, Spitler JD. Heating,

Center for Disease Control. Basic housing

ventilation, and air conditioning: analysis and design. 5th

inspection. Atlanta: US Department of Health

ed. Hoboken, NJ: John Wiley and Sons, Inc.; 2000.

and Human Services; 1976.

Kittle JL. Home heating and air conditioning systems.

Fairfax County. Fuel storage tanks. Fairfax, VA:

New York: McGraw-Hill; 1990.

Fairfax County; 2004. Available from URL:

http://www.co.fairfax.va.us/dpwes/construction/

Pita EG. Air conditioning principles and systems: an

fuel_tanks.htm.

energy approach. 4th ed. New York: Prentice Hall; 2001.

Wisconsin Department of Commerce.

Environmental services—residential fuel oil and

gasoline storage tanks. Madison, WI: Wisconsin

Department of Commerce; 2004. Available from

URL: http://www.commerce.state.wi.us/ER/ER-

BST-ResTk.html.

Michigan Department of Environmental Quality.

FAQ: Home heating oil tanks, Lansing, MI:

Michigan Department of Environmental Quality;

no date. Available from URL:

http://www.michigan.gov/deq/

0,1607,7-135-3311_4115_4238-9379--,00.html.

Healthy Housing Reference Manual

12-19

Chapter 13: Energy Efficiency

“Engineering is the science of economy, of conserving the

and lighting. Usage variables, such as taking excessively

energy, kinetic and potential, provided and stored up by

long showers, turning off lights when leaving rooms, or

nature for the use of man. It is the business of engineering to

using appliances at full or near-full capacity, may increase

utilize this energy to the best advantage, so that there may

or decrease energy use, depending on occupancy. Many

be the least possible waste.”

of these demands can be optimized in the design stage of

housing for new construction. However, when

William A. Smith

remodeling dwellings, making modifications to improve

1908

energy efficiency is often difficult. Preconstruction

consultations with architects and energy specialists can

Introduction

produce tradeoffs that retain the aesthetics and special

Using energy efficiently can reduce the cost of heating,

aspects of a dwelling, while making appropriate

ventilating, and air-conditioning, which account for a

investments in energy efficiency.

significant part of the overall cost of housing. Energy

costs recur month-to-month and are hard to reduce after

A price is paid for poor design and lack of proper

a home has been designed and built. The development of

insulation of dwellings, both in dollars for utility bills

an energy-efficient home or building must be thought

and in comfort of the occupants. The layout of rooms

through using a systems approach. Planning for energy

and overall tightness of a house in terms of air exchange

efficiency involves considering where the air is coming

affect energy requirements. In addition, home occupants

from, how it is treated, and where it is desired in the

and owners often are called on to make relatively minor

home. Improper use or installation of sealing and

decisions affecting total energy consumption, such as

insulating materials may lead to moisture saturation or

selecting lighting fixtures and bulbs and selecting settings

retention, encouraging the growth of mold, bacteria, and

for thermostats. Buying energy-efficient appliances can

viruses. In addition, toxic chemicals may be created or

save energy, but the largest reduction in energy use can

contained within the living environment. These building

be derived from major decisions, such as considering the

errors may result in major health hazards. The major

R-value of roof systems, insulation, and windows.

issues that must be balanced in using a systems approach

to energy efficiency are energy cost and availability, long-

R-values

term affordability and sustainability, comfort and

Thermal resistance (a material’s resistance to heat flow) is

efficiency, and health and safety.

rated by R-value. Higher R values mean greater

insulating power, which means greater household energy

Energy Systems

savings and commensurate cost savings. Table 13.1 is a

Making sound decisions in designing, constructing, or

guideline for choosing R-values that are right for a

updating dwellings will ensure not only greater use and

particular home based on the climate, household heating

enjoyment of the space, but also can significantly lower

system, and area in which it is located.

energy bills and help residents avoid adverse health

effects. Systematic planning for energy efficiency also can

Another way of understanding R-value is to see it as the

assist prospective homeowners in qualifying for

resistance to heat losses from a warmer inside

mortgages because lower fuel bills translate into lower

temperature to the outside temperature through a

total housing and utility payments. Some banks and

material or building envelope (wall, ceiling or roof

credit unions take this into account when qualifying

assembly, or window). Total heat loss is a function of the

prospective homeowners for mortgages. “Energy-

thermal conductivity of materials, area, time, and

efficient” mortgages provide buyers with special benefits

construction in a house.

when purchasing an energy-efficient home.

The R-value of thermal insulation depends on the type

Energy use and efficiency should be addressed in the

of material, its thickness, and its density. In calculating

context of selection of fuel types and appliances, location

the R-value of a multilayered installation, the R-values of

of the equipment, equipment sizing and backup systems,

the individual layers are added. Installing more insulation

and programmed use when making decisions on space

increases R-value and the resistance to heat flow.

heating, water heating, space cooling, window glazing,

The effectiveness of an insulated wall or ceiling also

Healthy Housing Reference Manual

13-1

Table 13.1. Cost-effective Insulation R-values for Existing Homes [a;1]

depends on how and where the insulation is installed. For

low as half the insulation’s R-value. With careful design,

example, insulation that is compressed will not provide its

this short-circuiting can be reduced.

full rated R-value. Also, the overall R-value of a wall or

ceiling will be somewhat different from the R-value of the

Roofs

insulation itself because some heat flows around the

Roofs are composite structures, with composite R-values.

insulation through the studs and joists. That is, the

The total R-value for the roof components shown in

overall R-value of a wall with insulation between wood

Figure 13.1 is 14.54 (Table 13.2). In general, a composite

studs is less than the R-value of the insulation itself

structure with a composite R-value of more than R-38

because the wood provides a thermal short-circuit around

provides a substantial barrier to heat loss. Of course, in

the insulation. The short-circuiting through metal

the winter the outside air temperature would vary

framing is much greater than that through wood-framed

significantly between locations such as Pensacola, Florida,

walls; sometimes the metal wall’s overall R-value can be as

and Fairbanks, Alaska, and would affect the cost-

13-2

Energy Efficiency

White Roof Surface

White roof surfaces combined with any of the measures

listed above will improve their performance significantly.

The white surface reflects much of the sun’s heat and

keeps the roof much cooler than a typical roof.

Insulation

Insulation forms a barrier to the outside elements. It can

help ensure that occupants are comfortable and that the

home is energy-efficient. Ceiling insulation improves

Figure 13.1. Roof Components [2]

comfort and cuts electricity or natural gas costs for

heating and cooling. For instance, the use of R-19

effectiveness of additional insulation and construction

insulation in houses in Hawaii [3] could have the

using various roofing components (Table 13.2).

following results:

The location of a house is usually a fixed variable in

• Reduce indoor air temperature by 4°F (-16°C) in

calculating R-values once the lot is purchased. However,

the afternoon.

the homeowner should consider the value of additional

insulation by comparing its cost with the savings resulting

• Lower the ceiling temperature, perhaps by more

from the increase in energy efficiency. Roof construction,

than 15°F (-9.4°C). Insulation [radiant barrier]

including components such as ridge vents and insulating

can reduce ceiling temperatures from 101°F

materials, is quite important and is often one of the more

(38°C) in bright sun on Oahu to 83°F (28°C).

cost-effective ways to lower energy costs.

(Figure 13.2).

Ridge Vents

• Reduce or eliminate the need for an air-

Ridge vents are important to roofs for at least three

conditioner.

reasons. First, ridge vents help lower the temperature in

the roof structure and, consequently, in the attic and in

Energy savings, of course, will vary depending on energy

the habitable space below. Second, ridge vents and

prices. The payback afforded by additional insulation or

rotating turbine vents help prolong the life of the roofing

investment in energy conservation measures is the average

materials, particularly asphalt shingles and plywood

amount of time it will require for the initial capital cost

sheathing. Third, ridge vents assist in air circulation and

to be recovered as a result of the savings in energy bills. A

help avoid problems with excessive moisture.

payback of 3 to 5 years might be economic, because the

average homeowner stays in a home that long. However,

Fan-powered Attic Ventilation

payback criteria can vary by individual, and renters, for

Attic ventilators are small fans that remove hot air and

example, often face the dilemma of not wanting to make

reduce attic temperature. Adequate inlet vents are

improvements for which they may not be able to fully

important. Typically these vents are located under the

realize the benefits. Described below are a few insulation

eaves of the house. The fan should be located near the

alternatives.

peak of the roof for best performance.

To achieve maximum effect, the method of installation

and type of insulation are of considerable importance.

The proper placement of moisture barriers is essential. If

insulation becomes moisture-saturated, its resistance to

energy loss is significantly reduced. Barriers to moisture

should be installed toward the living area because

significant moisture is generated in the home through

respiration, cooking, and the combustion of heating fuels.

Cellulose or fiberglass insulation is the most cost-effective

insulation. Blown-in cellulose or fiberglass and fiberglass

batts are similar in cost and performance. Recycled cellulose

Table 13.2. Potential Effects of Radiant Barriers [3]

Healthy Housing Reference Manual

13-3

from R-11 in relatively mild climate zones to R-38 in

New England, the northern Midwest, the Great Lakes,

and the Rocky Mountain states of Colorado and Wyoming.

Insulation requirements vary within climate zones in these

states and areas as well (for instance, mountainous areas

and areas farther north may have more heating-degree

days). The same logic of installing insulation applies to

both ceilings and walls: the insulation should provide a

barrier for heat and moisture transfer and buildup from

inside the dwelling, where temperatures will generally be

in the 68°F to 72°F (20°C to 22°C) range, compared

with the much colder or hotter temperatures outside. The

key to heat loss is the difference in temperatures and the

time that the heat transfer takes place over a given area or

surface. The choice of heating system, from gas/oil or heat

Figure 13.2. Potential Effects of Radiant Barriers [3]

pump, to electric resistance, will also affect the payback of

additional wall insulation due to variation in energy fuel

insulation may be available. For the best performance,

prices. For regions identified as “cold,” careful attention

insulation should be 5 to 6 inches thick. It can be installed

should be made in selecting energy fuel type; in

in attics of new and existing homes. It is typically the best

particular, a heat pump may not be a practical option.

choice for framed ceilings in new homes, but can be costly

to install in existing framed ceilings. It is very important

A homeowner exploring designs and construction methods

that this type of insulation be treated for fire resistance.

should examine the value of using structural insulated

panels. The incorporation of high levels of insulation

Foamboard (R-10, 1.5 to 2 inches) provides more insulation

directly from the factory on building wall and ceiling

per inch than does cellulose or fiberglass, but is also more

components makes them outstanding barriers to heat and

expensive. It is best where other insulation cannot be

moisture. These integrated systems, if appropriately used,

used, such as open-beam ceilings. It is applicable for new

can save substantial amounts of energy when compared

construction or when roofing is replaced on an existing

with traditional stick-built systems using 2×4 or 2×6

home. Two common materials are polystyrene and

lumber. Also, building energy-efficient features (as well as

polyisocyanurate. Polystyrene is better in moist conditions,

electrical, plumbing, and other elements) directly into the

and polyisocyanurate has a higher R-value per inch

building envelope at the factory can result in labor cost

(millimeter). However, some of these insulations present

savings over the more traditional methods of construction.

serious fire spread hazards. They should be evaluated to

ensure that they are covered with fire-retardant materials

Floor Insulation

and meet local fire and building codes.

Warm air expands and rises above surrounding cooler air.

This process of heat transfer is called convection. Warm

Radiant barrier insulation is a reflective foil sheet

air, which is lighter, rises and, as it cools, falls, creating a

installed under the roof deck like regular roof sheathing.

convection current of air. The two other processes of heat

The effectiveness of a radiant barrier (Figure 13.2)

transfer are conduction (kinetic energy transferred from

depends on its emissivity (the relative power of the surface

particle to particle, such as in a water- or electrically

to emit heat by radiation). In general, the shinier the foil

heated floor) and radiation (radiant energy emitted in the

the better. Radiant barrier insulation cuts the amount of

form of waves or particles such as in a fireplace or hot

heat radiated from the hot roof to the ceiling below. It

glowing heating element). Floor insulation limits all three

may be draped over the rafters before the roof is installed

modes of heat loss. A warmer floor reduces the temperature

or stapled to the underside of the rafters. The shiny side

difference that drives convection. Floor insulation also

should face downward for best performance. Some

directly impedes conduction and radiation to the colder

manufacturers claim that the radiant barrier prevents up to

air below the floor.

97% of the sun’s heat from entering the attic.

Batt Insulation

Wall Insulation

The advantage of floor insulation lies in adding extra

As shown in Table 13.1, it makes sense to insulate to high

R-value without a significant increase in cost. It is cheaper to

R-values in the ceiling. Insulation in walls should range

13-4

Energy Efficiency

put more insulation under the floor than to add foam

design and construction, “Buying a thicker batt may be a

sheathing or change the type of wall construction to

better option than trying to lift a thinner batt into the

accommodate greater insulation levels.

proper position. Material costs will climb slightly but labor

should be the same. Attaching the insulation support to the

Like walls, floor cavities should be completely filled with

bottom of the floor joist will be easier. It could also lead to a

insulation-without gaps, missing insulation, or cavity

higher quality job because there is less chance for

voids. Floor insulation must contact the subfloor and

compression or gaps” (Figure 13.4) [4].

both joists. In many cases, it is worth the extra cost to

buy enough insulation to fill the entire cavity.

In some areas, it’s common to hang plastic mesh over

floor joists. Installers drop the insulation onto the mesh

The amount of floor insulation required by some codes

before the subfloor is

can be less than the space available. For example, an R-19

installed. However,

fiberglass batt is 6¼ inches thick. A floor framed with

hanging the mesh

2×8s is about 7½ inches deep, while a 2×10 floor is

creates sagging bellies.

9½ inches deep. A builder following a code’s minimum

Insulation compresses

insulation level will leave extra space that will allow for

near the framing and

greater heat loss. To avoid this situation, the batt must be

sags in the middle. Mesh

pushed up into the cavity. With the proper support, this

should be attached to the

can be done. Springy metal rods are commonly used to

bottom of the floor

hold insulation up in the top of the floor cavity. Another

framing [4].

viable option is the use of plastic straps. Figure 13.3

shows batt insulation improperly applied to the floor

Each stage of increased

above a crawl space or a basement.

floor insulation, from

Table 13.3. Floor Insulation [5]

R-19 to R-30 or R-30 to

The thickness of typical fiberglass batts can assist the

R-38, can save energy over

designer and the builder in creating a floor system that

the life of the house. This energy translates into energy

works for the occupants. Table 13.3 shows a list of R-values,

savings that are multiples of the initial installation costs.

along with the associated batt thickness. Individual

Floor insulation will generate the greatest savings in

brands can vary by as much as 1 inch.

colder climates; in moderate climates, the target

insulation level should depend on economics.

Cavity Fill

According to Oikos, a commercial Web site devoted to

Blow-In Insulation

serving professionals whose work promotes sustainable

A blown-in insulation system allows the builder or

insulator to fill the entire cavity completely, even around

pipes, wires and other appurtenances. Using well-trained

installers will pay dividends in quality workmanship.

Doors

Today there is an endless variety of doors, ranging from

metal doors with or without insulation to hollow core to

solid wood. When properly installed into fitted frames,

doors serve as a heat barrier to maintain indoor temperatures.

Quality metal doors with insulation are best if they have a

thermal break between the interior and exterior metal

surfaces; this keeps heat from being transferred from one

side to the other.

Standard Doors

Because doors take up a small percentage of a wall,

insulating them is not as high a priority as is insulating

Figure 13.3. Common Floor Insulation Flaws [4.] Two common flaws in floor

insulation are gaps above the batt and compression of the batt in the cavity.

walls and ceilings. That said, heat loss follows the path of

least resistance; therefore, doors should be selected that

Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc.,

publisher of Oikos.com.

Healthy Housing Reference Manual

13-5

Figure 13.4a. Insulation Cavity Fill [4].

Figure 13.4b. Insulation Cavity Fill [4].

Lath provides a sturdy support for insulation.

Metal rods are available through insulation distributors. They are easy to use,

but insulation has to be compressed in the middle.

Figure 13.4c. Insulation Cavity Fill [4].

Figure 13.4d. Insulation Cavity Fill [4].

Mesh should be attached to the bottom of the framing. Draping the mesh over

Polypropylene twine resists rot, mildew, rodents, and other dangers. It is to be

the joists leads to compression that reduces insulating value.

stapled every 12 to 18 inches.

Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc., publisher of Oikos.com.

are functional and add to the energy-efficiency of the

provide good security, seal more tightly, tend to warp less.

house. Doors usually have lower R-values than the

Metal doors also are more soundproof than conventional

surrounding wall.

wood doors.

Storm doors can add R-1 to R-2 to the existing door’s R-

Sliding Glass Doors

value. They are a valuable addition to doors that are

Although sliding glass doors have aesthetic appeal, they

frequently used and those that are exposed to cold winds,

have very low R-values and hence are minimally energy

snow, and other weather. Screens allow natural breezes to

efficient. To improve the energy efficiency of existing

circulate air from outside, rather than totally relying on

sliding glass doors, the homeowner should ensure that

air-conditioning, which can be energy intensive.

they seal tightly and are properly weather-stripped.

Additionally, heavy insulated drapes with weights, which

When considering replacement doors, select insulated,

impede the airflow, can cut down on heat loss through

metal foam-core doors. Besides insulation, metal doors

sliding glass doors.

13-6

Energy Efficiency

Door Installation

Caulking

Doors must be installed as recommended by the

Caulks are airtight compounds (usually latex or silicone)

manufacturer. Care must be taken to be sure that doors

that fill cracks and holes. Before applying new caulk, old

are installed in a manner that does not trap moisture or

caulk or paint residue remaining around a window should

allow unintended introduction of air. Numerous types of

be removed using a putty knife, stiff brush, or special

sealing materials are available that range from foam to

solvent. After old caulk is removed, new caulk can then

plastic, to metal flanging and magnetic strips.

be applied to all joints in the window frame and the joint

between the frame and the wall. The best time to apply

Hot Water Systems

caulk is during dry weather when the outdoor

The hot water tank can be insulated to make it more

temperature is above 45°F (7.2°C). Low humidity is

efficient, unless the heat loss is used within the space

important during application to prevent cracks from

where it is located. Special insulation is available for this

swelling with moisture. Warm temperatures are also

type of appliance, and insulating it will reduce the energy

necessary so the caulk will set properly and adhere to the

required to deliver the hot water needed by the occupants

surface [5].

of the dwelling. Of course, any pipe that is subject to

extreme temperatures also should be insulated to decrease

Weather-stripping

heat loss.

Weather-stripped frames are narrow pieces of metal, vinyl,

rubber, felt, or foam that seal the contact area between

Windows

the fixed and movable sections of a window joint. They

Windows by nature are transparent. They allow occupants

should be applied between the sash and the frame, but

of a dwelling to see outside and bring in sunlight and

should not interfere with the operation of the window [6].

heat from the sun. They make space more pleasant and

often provide lighting for tasks undertaken in the space.

Replacing Window Frames

Especially in the winter, these desirable characteristics

The heat-loss characteristics and the air tightness of a window

offset the heat loss. Heat gain in the summer through

vary with the type and quality of the window frame. The

windows can be undesirable.

types of available window frames are fixed-pane,

casement, double- and single-hung, horizontal sliding,

Rather than give them up, it is important to use windows

hopper, and awning. Each type varies in energy efficiency.

prudently and to keep energy considerations in mind in

their design and their insulating characteristics (air, glass,

Correctly installed fixed-pane windows are the most

plastic, or gas filler). Good design takes advantage of day

airtight and inexpensive choice, but are not suited to

lighting. Weather-stripping and sealing leaks around

places that require ventilation. The air infiltration

windows can enhance comfort and energy savings. Energy

properties of casement windows (which open sideways

Star windows are highly recommended. Housekeeping

with hand cranks), awning windows (which are similar to

measures can improve the efficiency of retaining heat.

casement windows but have hinges at the top), and

Heat loss follows the path of least resistance: caulking,

hopper windows (inverted awning windows with hinges

weather-stripped framing, and films can help. These

at the bottom) are moderate. Double-hung windows,

measures are relatively labor intensive, low to very low in

which have top and bottom sashes (the part of the

cost, and can be quite satisfying to the homeowner if

window that can slide), tend to be leaky. The advantage

accomplished correctly. On the other hand, it is not easy

of the single-hung window over the double-hung is that it

finding the perfect materials or even replacement parts for

tends to restrict air leakage because there is only one

old windows.

moving part. Horizontal sliding windows, though suitable

for small, narrow spaces, provide minimal ventilation and

When working with older windows, remember that there

are the least airtight.

is the risk for leaded paint and the dispersion of toxic lead

dust into the work area. Please refer to the lead section of

In buildings with large older windows, there are often

Chapter 5, Indoor Air Pollutants and Toxic Materials.

weight cavity areas that hide counter balances that make

it easy to raise and lower heavy windows. These areas

Caulking and Weather-Stripping

should be insulated to reduce energy loss.

According to the U.S. Department of Energy, caulking

and weather-stripping have substantial housekeeping

benefits in preventing energy loss or unwanted heat gain.

Healthy Housing Reference Manual

13-7

Tinted Windows

•

Heat-absorbing glass is specially tinted to absorb

Another way to conserve energy is the installation of

approximately 45% of the incoming solar energy;

tinted windows. Window tinting can be installed that will

some of this energy passes through the pane.

both conserve energy and also prevent damaging ultraviolet

light from entering the room and potentially fading wood

•

Reflective glass has a reflective film that reduces heat

surfaces, fabrics, and carpeting. Low-emissivity coatings,

gain by reflecting most of the incident solar radiation.

called low-e coatings, are also available. These coatings are

designed for specific geographic regions.

•

Plastic glazing materials such as acrylic,

polycarbonate, polyester, polyvinyl fluoride, and

Reducing Heat Loss and Condensation

polyethylene are stronger, lighter, cheaper, and

The energy efficiency of windows is measured in terms of

easier to cut than glass. However, they are less

their U-values (measure of the conductance of heat) or

durable and tend to be affected by the weather

their R-values. Besides a few highly energy-efficient

more than glass is.

exceptions, window R-values range from 0.9 to 3.0.

When comparing different windows, it is advisable to

•

Storm windows can improve the energy efficiency

focus on the following guidance for R- and U-values:

of single-pane windows. The simplest example of

storm windows would be plastic film, available in

• R- and U-values are based on standards set by the

prepackaged kits, taped to the inside of the

American Society of Heating, Refrigerating, and

window frame. Because this can affect visibility

Air-Conditioning Engineers [7].

and be easily damaged, a better choice would be

to attach rigid or semirigid plastic sheets such as

• R- and U-values are calculated for the entire

plexiglass, acrylic, polycarbonate, or fiber-

window, which includes the frame.

reinforced polyester directly to the window frame

or mounting it in channels around the frame on

• R- and U-values represent the same style and size

the outside of the building. Care should be taken

of windows.

in installation to avoid ripples or blemishes that

will affect visibility.

The R-value of a window in an actual house is affected by

the type of glazing material, the number of layers of glass,

Layering

the amount of space between layers and the nature of the

The insulating capacity of single-pane windows is minimal,

gas filling them, the heat-conducting properties of the frame

around R-1. Multiple layers of glass can be used to increase

and spacer materials, and the airtightness associated with

the energy efficiency of windows. Double- or triple-pane

manufacturing.

windows have air-filled or gas-filled spaces, coupled with

multiple panes that resist heat flow. The space between

For windows, rating and approval by the National Fenestration

the panes is critical because the air spaces that are too

Rating Council or equivalent rating and approval is

wide (more than 5/8 inch) or too narrow (less than ½ inch)

strongly recommended [8].

allow excessive heat transfer. Modern windows use inert

gases, such as argon and krypton, to fill the spaces

Please refer to the window section of Chapter 6, Housing

between panes because these gases are much more

Structure.

resistant to heat flow than air is. These gas-filled windows

are more expensive than regular double-pane windows.

Glazing

Glazing refers to cutting and fitting windowpanes into

• Frame and spacer materials may be aluminum,

frames. Glass has been traditionally the material of choice

wood, vinyl, fiberglass, or a combination of these

for windowpanes, but that is changing. Several new

materials, such as vinyl- or aluminum-clad wood.

materials are available that can increase the energy

efficiency of windows. These include the following:

• Aluminum frames are strong and are ideal for

customized window design, but they conduct heat

• Low-emissivity (low-e) glass uses a surface coating

and are prone to condensation. The deterioration

to minimize transmission of heat through the

of these frames can be avoided by anodizing or

window by reflecting 40% to 70% of incident

coating. Their thermal resistance can be boosted

heat while letting full light pass through the pane.

13-8

Energy Efficiency

using continuous strips of plastic between the

Solar Energy

interior and exterior of the frame.

Solar energy is a form of renewable energy available to

homeowners for heating, cooling, and lighting. The more

•

Wood frames are superior to aluminum frames in

energy-efficient new structures are designed to store solar

having higher R-values, tolerance to temperature

energy. Remodeled structures may be retrofitted to increase

extremes, and resistance to condensation. On the

energy efficiency by improving insulation characteristics,

other hand, wood frames require considerable

improving airflow and airtightness of the structure, and

maintenance in the form of painting or staining.

enhancing the ability to use solar energy. Solar energy

Improper maintenance can lead to rot or warping.

systems are active and passive. Whereas active solar systems use

some type of mechanical power to collect, store, and

•

Vinyl window frames made from polyvinyl

distribute the sun’s energy, passive systems use the

chloride are available in a wide range of styles and

materials and design elements in the structure itself.

shapes, can be easily customized, have moderate

R-values, and can be competitively priced. Large

Active Solar Systems

windows made of vinyl frames are reinforced

Active solar systems use devices to collect, convert, and

using aluminum or steel bars. Vinyl windows

deliver solar energy. Solar collectors on roofs or other

should be selected only after consideration of the

south-facing surfaces can be used to heat water and air

concerns surrounding the use of vinyl materials

and generate electricity. Active solar systems can be

and their off-gassing characteristics.

installed in new or existing buildings and periodically

need to be inspected and maintained. Active solar energy

•

Fiberglass frames have the highest R-values and

equipment consists of collectors, a storage tank, piping or

are not given to warping, shrinking, swelling,

ductwork, fans, motors, and other hardware. Flat panel

rotting, or corroding. Fiberglass is not weather-

collectors (Figure 13.5) can be placed on the roof or on

resistant, so it should also be painted. Some

walls. Typically, the collector will be a sandwich of one or

fiberglass frames are hollow; others are filled with

two sheets of glass or plastic and another air space above a

fiberglass insulation.

metal absorber plate, which is painted black to enhance

heat absorption. After collection, when the sun’s energy is

•

Spacers separating multiple windowpanes in a

converted to heat, a transfer is made to a liquid storage

window use aluminum to separate glass in

tank. The heated liquid travels through coils in the hot

multipane windows, but it conducts heat. In

water tank, and the heat is transferred to the water and

addition, in cold weather, the thermal resistance

perhaps the heating system. Most hot water systems use a

around the edge of such a window is lower than

liquid collector system because it is more efficient and less

that in the center, allowing heat to escape and

costly than an air-type system.

condensation to occur along the edges.

In the southwest United States, solar roof ponds have

•

Polyvinyl chloride foam separators placed along

become popular for solar cooling. Evaporative cooling

the edges of the frame reduce heat loss and

systems depend on water vaporization to lower the

condensation. Window manufacturers use foam

temperature of the air. These have been shown to be more

separators, nylon spacers, and insulation materials

effective in dry climates than in areas with extremely high

such as polystyrene and rock wool insulation

relative humidity.

between the glass panes inside windows.

In certain climates, like those in the Hawaiian Islands,

Other Options

using solar energy is cost-effective for providing hot water.

Shades, shutters, and drapes used on windows inside the

house reduce heat loss in the winter and heat gain in the

summer. The heat gain during summer can also be minimized

by the use of awnings, exterior shutters, or screens. These

cost-effective window treatments should be considered before

deciding on window replacement. By considering orientation,

day lighting, storage of or reflection of energy from

sunshine, and materials used within the house and on the

building envelope, heat loss and gain can be decreased.

Figure 13.5. Solar Panels

Healthy Housing Reference Manual

13-9

Some builders even include it as a standard feature in

Energy Star is a program supported and promoted by the

their homes. The total cost to the homeowner of solar

U.S. Environmental Protection Agency (EPA) that helps

energy systems consists of the capital, operational, and

individuals protect the environment through superior

maintenance costs. The real cost of capital may be

energy efficiency. For the individual in his or her home,

lowered by the availability of tax credits offered at the

energy-efficient choices can save families about one third

federal (to lower federal income taxes) and state levels.

on their energy bill, with similar savings of greenhouse

gas emissions, without sacrificing features, style, or

Homeowners and builders can benefit from tax credits

comfort. When replacing household products, look for

because they lower the total upfront investment cost of

ones that have earned the Energy Star; these products

installing active solar systems. This is the major portion of

meet strict energy-efficiency guidelines set by EPA and

the total cost of using solar energy, because operation and

the U.S. Department of Energy. When looking for a new

maintenance costs are small in comparison to initial

home, look for one that has earned the Energy Star

system costs.

approval. If you are planning to make larger

improvements to your home, EPA offers tools and

Passive Solar Systems

resources to help you plan and undertake projects to

Buildings designed to use passive solar energy have

reduce your energy bills and improve home comfort [9].

features incorporated into their design that absorb and

In 2004 alone, Americans, with the help of Energy Star,

slowly release the sun’s heat. In cold climates, the design

saved enough energy to power 24 million homes and

allows the light and heat of the sun to be stored in the

avoid greenhouse gas emissions equivalent to those from

structure, while insulating against the cold. In warm

20 million cars-all while saving $10 billion.

climates, the best effect is achieved by admitting light

while rejecting heat. A building using passive solar

Conducting an Energy Audit

systems may have the following features in the floor plan:

Energy audits can help identify areas where energy

investments can be made, thereby reducing energy used in

• Large south-facing windows

lighting, heating, cooling, or meeting other demands of

housing occupants. An inspection can evaluate the

• Small windows in other directions, particularly on

worthiness or compliance with codes of energy-saving

the north side of the structure

measures, including accepted or written standards. For

example, if a new addition requires the equivalent of R-19

• Designs that allow daylight and solar heat to

insulation in the ceilings, this can be validated in the

permeate the main living areas

inspection process. Whereas an audit is generally

informational, an inspection should validate that

• Special glass to block ultraviolet radiation

materials and workmanship have yielded a structure that

protects the occupants from the elements, such as rain,

• Building materials that absorb and slowly

snow, wind, cold, and heat. Potentially hazardous

reradiate the solar heat

situations within a structure should be evaluated in an

inspection. The overall goal of a housing inspection in the

• Structural features such as overhangs, baffles, and

case of energy efficiency is to identify potential hazardous

summer shading to eliminate summer

conditions and help to create conditions under which the

overheating.

health and welfare of the occupants can be enhanced,

rather than put at risk.

Passive design can be a direct-gain system when the sun

shines directly into the building, thereby heating it and

The housing inspector should be aware that there is

storing this heat in the building materials (concrete, stone

variation (sometimes quite significant differences) in

floor slabs, and masonry partitions). Alternatively, it may

heating degree days or cooling loads and in relative

be an indirect gain system where the thermal mass is

humidity conditions within given regions. Local and

located between the sun and the living space. Isolated

regional topography, as well as site conditions, can affect

gain is yet another type of system that is separated from

temperatures and moisture.

the main living area (such as a sunroom or a solar

greenhouse), with convective loops for space conditioning

Numerous Web sites listed in this chapter’s Additional

into the living space.

Sources of Information section discuss the procedures for

conducting energy audits. Local and regional utilities

13-10

Energy Efficiency

often offer audit services and assist with selecting cost-

9. US Environmental Protection Agency. What is

effective conservation measures for given areas of the

Energy Star? Washington, DC: US Environmental

United States.

Protection Agency; no date. Available from URL:

http://www.energystar.gov/

References

index.cfm?c=about.ab_index.

Lawrence Berkeley National Laboratory. Energy

star insulation project: R-value guidelines.

Additional Sources of Information

Berkeley, CA: Lawrence Berkeley National

Alliance to Save Energy. Save energy at home. Available

Laboratory; 2004. Available from URL:

from URL: http://www.ase.org/section/

http://enduse.lbl.gov/Projects/Rvalue.html.

_audience/educators/edsavhome/.

RoofHelp.com. R-value. Fort Worth, TX:

Christian J, Kosnay J. Home Calculating whole wall R-

RoofHelp; 1999. Available from URL:

values on the Net. Energy Magazine Online,

http://www.roofhelp.com/Rvalue.htm.

November/December 1999.

State of Hawaii, Department of Business,

Energy Information Administration. Available from URL:

Economic Development, and Tourism, Energy

http://www.eia.doe.gov.

Resources and Technology Division. Ceiling

insulation. Honolulu, HI: State of Hawaii,

Environmental Solar Systems. Available from URL:

Department of Business, Economic Development,

http://www.environmentalsolarsystems.com/systems/.

and Tourism; no date. Available from

URL:http://www.hawaii.gov/dbedt/

Enviro$en$e: Common sense solutions to environmental

ert/rf_insul.html.

problems. Available from URL: http://es.epa.gov/.

Oikos. Filling a floor with batt insulation. Energy

Florida Power and Light. Building shell: insulation.

Source Builder 1995 [Apr]; 38. Available from

Available from URL: http://www.fpl.com/savings/

URL: http://oikos.com/esb/38/

energy_advisor/PA_45.html.

floorinsulation.html.

Florida Power and Light. Online home energy survey.

US Department of Energy. Energy savers: fact

Available from URL:

sheets. Washington, DC: US Department of

http://www.fpl.com/home/ohes/contents/

Energy; no date. Available from URL:

online_home_energy_survey.shtml.

http://www.eere.energy.gov/consumerinfo/

factsheets.html.

Hawaii Department of Business, Economic Development

and Tourism. Ceiling insulation. Available from URL:

US Department of Energy. Advances in glazing

http://www.state.hi.us/dbedt/ert/rf_insul.html.

materials for windows. Washington, DC: US

Department of Energy; 1994.

National Association of State Energy Officials. Available

from URL: http://www.naseo.org.

American Society of Heating, Refrigerating and

Air-Conditioning Engineers (ASHRAE).

Nexus Energyguide. Available from URL:

Standards; no date. Atlanta: American Society of

http://www.energyguide.com/default.asp.

Heating, Refrigerating and Air-Conditioning

Engineers. Available from URL:

Oak Ridge National Laboratory Buildings Technology

http://www.ashrae.org.

Center. Available from URL:

http://www.ornl.gov/ORNL/BTC.

National Fenestration Rating Council. Search for

energy performance ratings. Silver Spring, MD:

Oak Ridge National Laboratory. Whole-wall thermal

National Fenestration Rating Council; no date.

calculator performance. Available from URL:

Available from URL: http://www.nfrc.org/

http://www.ornl.gov/roofs+walls/

windowshop/surveybegin.aspx.

whole_wall/wall-a30.html.

Healthy Housing Reference Manual

13-11

Oikos. Whole wall R-value ratings. Energy Source Builder

#47; October 1996. Available from URL:

http://oikos.com/esb/47/wholewall.html.

RoofHelp.com. R-value. Available from URL:

http://www.roofhelp.com/Rvalue.htm.

Senate Committee on Energy and Natural Resources.

Highlights of the Energy Policy Act of 2003 and the

Energy Tax Incentives Act of 2003. Available from URL:

http://energy.senate.gov/news/rep_release.cfm?id=203374.

Trandt J. Americans want energy efficiency. Available

from URL: http://healthandenergy.com/

energy_efficiency.htm.

US Department of Energy, Energy Efficiency and

Renewable Energy. Building envelope. Available from

URL: http://www.eere.energy.gov/

EE/buildings_envelope.html.

US Department of Energy, Energy Information

Administration. Available from URL: http://eia.doe.gov/.

US Environmental Protection Agency. Available from

URL: http://www.epa.gov.

US Environmental Protection Agency, Energy Star.

Available from URL: http://www.energystar.gov.

Wilson A. Thermal mass and R-value: making sense of a

confusing issue. EBN 1998 7(4). Available from URL:

http://www.buildinggreen.com/features/tm/thermal.cfm.

World Energy Efficiency Association. Available from

URL: http://www.weea.org/.

13-12

Energy Efficiency

Chapter 14: Residential Swimming Pools and Spas

“Most people assume if their young child falls into the pool,

•

Fences and walls should be at least 4 feet high

there will be lots of splashing and screaming, and plenty of

and installed completely around the pool. The

time to react. In reality, a child slips into the water and

fence should be no more than 2 inches above

often goes under the surface. These drownings can happen

grade. Openings in the fence should be a

quickly and silently-without warning.”

maximum of 4 inches. A fence should be difficult

to climb over.

Hal Stratton, Chair

U.S. Consumer Product Safety Commission,

•

Fence gates should be self-closing and self-

2002-Present

latching. The latch should be out of a small

child’s reach. The gate should open away from

Introduction

the pool; the latch should face the pool.

Swimming is one of the best forms of exercise available

and having a residential swimming pool also can provide

•

Any doors with direct pool access should have an

much pleasure. Nevertheless, it takes a great deal of work

audible alarm that sounds for 30 seconds. The

and expense to make and keep the pool water clean and

alarm control must be a minimum of 54 inches

free of floating debris. Without a doubt, a properly

high and reset automatically.

maintained and operated pool is quite rewarding. Home

pools, however, are sometimes referred to as attractive

•

If the house forms one side of the barrier to the

nuisances or hazards. It is essential to be able to evaluate

pool, then doors leading from the house to the

the risks associated with a pool. A regulatory agent or

pool should be protected with alarms that

consultant must understand the total engineered pool

produce a sound when a door is opened.

system and be capable of identifying all equipment,

valves, and piping systems. The piping system for a pool

•

Young children who have taken swimming

should be color-coded to assist the pool operator or the

lessons should not be considered “drown proof”;

owner to determine the correct way to operate the

young children should always be watched

swimming pool. The specific goal is to protect the

carefully while swimming.

owners, their families, and others who may be attracted

to a residential pool.

•

A power safety cover-a motor-powered barrier

that can be placed over the water area-can be

Residential pools and spas should provide clean, clear water;

used when the pool is not in use.

water free of disease agents; and a safe recreational

environment. In addition, residential pools and spas

•

Rescue equipment and a telephone should be

should have effective, properly operating equipment and

kept by the pool; emergency numbers should be

effective maintenance and operation.

posted. Knowing cardiopulmonary resuscitation

(CPR) can be a lifesaver.

Childproofing

Although it seems obvious, close supervision of young

•

For aboveground pools, steps and ladders should

children is vital for families with a residential pool. A

be secured and locked or removed when the pool

common scenario is a young child leaving the house without

is not in use.

the parent or caregiver realizing it. Children are drawn to

water, and they can drown even if they know how to swim.

•

Babysitters should be instructed about potential

All children should be supervised at all times while in

hazards to young children in and around

and around a pool.

swimming pools and their need for constant

supervision.

The key to preventing pool tragedies is to provide layers

of protection. These layers include limiting pool access, using

•

If a child is missing, the pool should always be

pool alarms, closely supervising children, and being prepared

checked first. Seconds count in preventing death

in case of an emergency. The U.S. Consumer Product Safety

or disability.

Commission (CPSC) offers these tips to prevent drowning:

Healthy Housing Reference Manual

14-1

•

Pool alarms can be used as an added precaution.

• A clear view of the pool from the house should be

Underwater pool alarms can be used in

ensured by removing vegetation and other

conjunction with power safety covers. CPSC

obstacles that block the view.

advises consumers to use remote alarm receivers so

the alarm can be heard inside the house or in

Hazards

other places away from the pool area.

Numerous issues need to be considered before building

residential pools: location of overhead power lines,

•

Toys and flotation devices should be used in pools

installation and maintenance of ground fault circuit

only under supervision; they should not be used

interruptors, electrical system grounding, electrical wiring

in place of supervision.

sizing, location of the pool, and type of vegetation near

the pool. The commonly used solar covers that rest on the

•

Well-maintained rescue equipment (including a

surface of the pool and amplify sunlight do an excellent

ring buoy with an attached line and/or a

job of increasing the pool temperature, and they also

shepherd’s crook rescue pole should be kept by the

increase the risk for drowning. If children or pets fall in

pool.

and sink below the cover, it can be nearly impenetrable if

they attempt to surface under it.

•

Emergency procedures should be clearly written

and posted in the pool area.

Winterizing the pool also can be hazardous. The pool

water in most belowground pools is seldom drained

•

All caregivers must know how to swim, know how

because of groundwater pressure that can damage the

to get emergency help, and know CPR.

structure of the pool. Therefore, water in most home

pools is only lowered below the frost line for winter

•

Children should be taught to swim (swimming

protection. In these cases, a pool cover is installed to keep

classes are not recommended for children under

debris and leaves from filling the pool in the winter

the age of 4 years) and should always swim with a

months. The pool cover becomes an excellent mosquito-

buddy.

breeding area before the pool is reopened in the spring

because of the decomposing vegetation that is on the pool

•

Alcohol should not be consumed during or just

cover, the rain that accumulates on the top of the pool

before swimming or while supervising children.

cover during the winter, and the eggs laid on the pool

cover in early fall and early spring. The cover also

•

To prevent choking, chewing gum and eating

provides ideal conditions for mosquitoes to breed:

should be avoided while swimming, diving, or

stagnant water, protection from wind that can sink

playing in water.

floating eggs, the near absence of predators, and warm

water created by the pool cover collecting heat just below

•

Water depth should be checked before entering a

the surface (Figure 14.1).

pool. The American Red Cross recommends 9 feet

as a minimum depth for diving and jumping.

Public Health Issues

Current epidemiologic evidence indicates that correctly

•

Rules should be posted in easily seen areas. Rules

constructed and operated swimming pools are not a

should state “no running,” “no pushing,” no

drinking,” and “never swim alone.” Be sure to

enforce the rules.

•

Tables, chairs, and other objects should be placed

well away from the pool fence to prevent children

from using them to climb into the pool area.

•

When the pool is not in use, all toys should be

removed to prevent children from playing with or

reaching for them and unintentionally falling into

the water.

Figure 14.1. Pool Cover

14-2

Residential Swimming Pools and Spas

major public health problem. They are preferable to

Injuries

bathing beaches because of the engineered controls

Injuries and drowning deaths are by far the greatest problem

designed into pools. Poorly designed or operated pools,

at swimming pools. Lack of bather supervision is a prime

however, can be major public health hazards. Data from

cause, as is the improper construction, use, and maintenance

CDC between 1999 and 2000 show that 59 disease

of equipment. Injuries include evisceration, electrocution,

outbreaks from 23 states were attributed to recreational

entrapment, and entanglement. Some particular problem

water exposure and affected an estimated 2,093 people.

areas include the following:

Of the 59 recreational outbreaks, 44 (74.6%) were of

known infectious etiology. Of the 36 outbreaks involving

• lose or poorly located diving board,

gastroenteritis, 17 (47.2%) were caused by parasites;

(25.0%) by bacteria; 3 (8.3%) by viruses; 1 (2.8%) by a

• slippery decks or pool bottoms,

combination of parasites and bacteria, and the remaining

6 (16.7%) were of unknown cause. Of the

• poorly designed or located water slides,

23 nongastroenteritis-related recreational outbreaks, seven

were attributed to Pseudomonas aeruginosa, four to free-

• projecting or ungrated pipes and drains that can

living amoebae, one to Leptospira species, one to

catch hair or body parts,

Legionella species, and one to bromide. Sixteen of the

17 parasitic recreational water outbreaks involving

• drain grates of inadequate size,

gastroenteritis; nine (24.3%) were outbreaks of dermatitis;

and six (16.2%) were caused by Cryptosporidium parvum.

• improperly installed or maintained electrical

The seventeenth outbreak was caused by Giardia lamblia

equipment, and

(intestinalis). In 1999, an outbreak of Campylobacter

jejuni was associated with a private pool that did not have

• improperly vented chlorinators and mishandled

continuous chlorine disinfection and reportedly had

chlorine materials.

ducks swimming in the pool [1].

Water Testing Equipment

Diseases

It is essential that correct equipment be used and maintained

•

Intestinal diseases: Escherichia coli O157:H7,

for assessing the water quality of both swimming pools

typhoid fever, paratyphoid fever, amoebic dysentery,

and spas. The operators of pool and spas need to monitor

leptospirosis, cryptosporidiosis (highly chlorine

a wide range of chemicals that influence pool operations

resistant), and bacillary dysentery can be a

and water quality. Their equipment should test for chlorine,

problem where water is polluted by domestic or

bromine, pH, alkalinity, hardness, and cyanuric acid build

animal sewage or waste. Swimming pools have

up. The chlorine should be measurable at a range of 0 to

also been implicated in outbreaks of leptospirosis.

10 parts per million (ppm). Water pH levels should be

accurately measured with an acid or base test. A kit to

•

Respiratory diseases: Colds, sinusitis, and septic

check pool chemical levels usually includes N,N-diethyl-

sore throat can spread more readily in swimming

p-phenylene-diamine (DPD) tablet tests for free and total

areas as a result of close contact, or improperly

chlorine, and other one-step tablet tests for pH, total

treated pool water, coupled with lowered

alkalinity, calcium hardness, and cyanuric acids. The

resistance because of exertion.

homeowner should determine acid or base demand using

an already reacted pH sample in dropper bottles. Paper

•

Eye, ear, nose, throat, and skin infections: The

test strips with multiple tests (including chlorine, bromine,

exposure of delicate mucous membranes, the

and pH) are also available, but the reliability of these tests

movement of harmful organisms into ear and

varies greatly. If used, they should be kept fresh, protected

nasal passages, the excessive use of water-

from heat and moisture, and checked against other test

treatment chemicals, and the presence of harmful

systems periodically if water quality problems persist.

agents in water can contribute to eye, ear, nose,

throat, and skin infections. Close physical contact

Swimming pools are engineered systems, with demanding

and the presence of fomites (such as towels) also

safety and sanitary requirements that result in rather

help to spread athlete’s foot, impetigo, and dermatitis.

sophisticated design standards and water treatment

systems. The size, shape, and operating system of the pool

is based on the following considerations:

Healthy Housing Reference Manual

14-3

• the intended use of the pool and the maximum

time (T) in minutes (CT value = C×T ). The CT value

expected bather loading;

for Giardia is 45 and the value for Cryptosporidia is 9,600. If

a different chlorine concentration or inactivation time is

• the selection of skimmers, scuppers, or gutters,

used, CT values must remain the same. For example, to

depending on the purpose, size, and shape of the

determine the length of time needed to disinfect a pool at

pool;

15 ppm after a diarrheal accident, the following formula

is used: C×T = 9,600. Solve for time: T= 9,600÷15 ppm

• the recirculation pump, whose horsepower and

= 10.7 hours. It would, thus, take 10.7 hours to inactivate

impeller configuration are based on the distance,

Cryptosporidia at 15 ppm. You can do the same for

volume, and height of the water to be pumped;

Giardia by using the CT of 45.

• the filters, which are sized on the volume of water

CDC has Web sites that contain excellent information

to be treated and the maximum gallons (liters) of

about safe swimming recommendations, recreational

water per minute that can be delivered by the

water diseases, and disinfection procedures for fecal

pump and the type of filter media selected; and

accidents [3,4].

• the chemical feeder sizes and types, which are

Content Turnover Rate

based on the chemicals used, total quantity of the

The number of times a pool’s contents can be filtered

water in the system, expected use rates, and

though its filtration equipment in a 24-hour period is the

external environmental factors, such as quantity of

turnover rate of the pool. Because the filtered water is

sunlight and wind that affect the system.

diluted with the nonfiltered water of the pool, the

turbidity continually decreases. Once the pool water has

Disinfection

reached equilibrium with the sources of contamination, a

The length of time it takes to disinfect a pool depends,

6-hour turnover rate will result in 98% clarification if the

for example, on the type of fecal accident and the

pool is properly designed. A typical-use pool should have

chlorine levels chosen to disinfect the pool. If a fecal

a pump and filtration system capable of pumping the

accident is a formed stool, the faollowing chlorine levels

entire contents of the pool though the filters every 6 hours. To

will determine the times needed to inactivate Giardia:

determine compliance with this 6-hour turnover standard,

the following formula is used:

Chlorine Levels (ppm)

Disinfection Time

1.0

45 minutes

Turnover rate = pool volume (gallons)/

2.0

25 minutes

flow rate×60 (minutes in hour)

3.0

19 minutes

Following is a sample calculation of the pool content

These times are based on a 99.9% inactivation of Giardia

turnover rate using the rate of flow reading from the flow

cysts by chlorine, pH 7.5, and 77°F (25°C). The times

meter:

were derived from the EPA LT1ESWTR Disinfection

Profiling and Benchmarking Technical Guidance Manual

Turnover rate = 90,000 (gallons in pool)/

[2]. These times do not take into account “dead spots”

180 gallons per minute×60 (minutes in hour)

and other areas of poor pool water mixing.

8.3-hour turnover rate = 90,000 (pool volume in

If the fecal accident is diarrhea, the following chlorine

gallons)/10,800

levels will determine the times needed to inactivate

Cryptosporidia:

The above pool would not meet the required turnover

rate of 6 hours. The cause could be improperly sized

Chlorine Levels (ppm)

Disinfection Time

piping or restrictions in the piping, an undersized pump,

1.0

6.7 days

or undersized or clogged filters. This turnover rate would

10.0

16 hours

probably result in cloudy water if the pool is used at the

20.0

8 hours

normal bather load. The decreased circulation would also

make it difficult for the disinfecting equipment to meet

A CT value is the concentration (C) of free available

the required levels.

chlorine in parts per million (ppm) multiplied by the

14-4

Residential Swimming Pools and Spas

Filters

backwashing will depend on many factors, including the

Pool filters are not designed to remove bacteria, but to

size of your filter, flow rate of your plumbing, and the

make the water in the pool clear. Normal tap water looks

bather load in your pool. When the pressure reading on

quite dingy if used to fill a pool and, in some cases, the

the filter reaches the level set by the manufacturer’s

bottom of the pool is not visible. The maximum turbidity

manual, it will be ready for backwashing.

level of a pool should be less than 0.5 nephelometric

turbidity units. Pool filters should be sized to ensure that

Filter Loading Rates

the complete contents of the pool pass through the filter

The specification plate on the side of approved residential

once every 6 hours. Home pools typically use one of three

or commercial swimming pool filters contains such

types of filters.

information as the manufacturer, type of filter, serial

number, surface area, and designed loading rate. Knowing

High-rate Sand Filters

the surface area of the filter permits calculation of the

High-rate sand filters were introduced more than 30 years

number of gallons flowing through the filter per minute.

ago and reduced the size of the conventional sand filter by

An excessive flow rate can push the media into the pool

80%. The sand filter is the most popular filter on the

or force pool solids and materials thought the media,

market. High-rate sand filters use a silica sand that has

resulting in turbid water. Figure 14.2 shows a typical

been strained to give it a uniform size. It is referred to as

home pool treatment system. Regulations typically specify

pool-grade sand #20 silica. The sand is normally

how much water can be filtered through the various types

0.45 millimeters (mm) to 0.55 mm in diameter. As water

of pool filtration systems.

passes through the filter, the sharp edges of the sand trap

the dirt from the pool water. When the backpressure of

Disinfectants

the filter increases to 3 to 5 psi, the filter needs to be

Many disinfectants are used in pools and spas around the

cleaned. This is usually accomplished by reversing the

world, including halogen-based compounds (chlorine,

flow of the water through the filter and flushing the dirt

bromine, iodine), ozone, and ultraviolet light with

out the waste pipe until the water being discharged

hydrogen peroxide. Those used most often are chlorine,

appears clear. These filters perform best when used at

bromine, and iodine, and each has advantages and limitations.

pressure levels below 15 to 20 gallons per minute,

depending on the manufacturer of the filter.

Cartridge Filters

Cartridge filters have been around for many years, but

only recently have gained in popularity in the pool

industry. They are similar to the filter on a car engine.

The water is passed through the cartridge and returned to

the pool. When the pressure of a cartridge filter increases

approximately 5 psi, the pump is turned off; and the top

of the filter is removed. The cartridge is removed and

either discarded and replaced or, in some cases, washed.

Diatomaceous Earth

Diatomaceous earth (DE) is a porous powder made from

the skeletons of billions of microscopic animals that were

buried millions of years ago. There are two primary types

of DE filters, but they both work the same way. Water

comes into the filter, passes through the DE, and is

returned to the pool. If properly sized and operated, DE

filters are considered by some to provide the highest

quality of water. They are capable of filtering the smallest

particle size of all the filter types. It is usually adequate to

change the DE once every 30 days. However, if your pool

water is very dirty, it is not uncommon to change it

3-4 times a day until the water is clear. The frequency of

Figure 14.2. Typical Home Pool Equipment System

Healthy Housing Reference Manual

14-5

Chlorine—Pools can be disinfected with chlorine-

the water can interfere with ultraviolet light transmission.

releasing compounds, including hypochlorite salt

The water must be adequately treated before ultraviolet

compounds. Calcium hypochlorite is inexpensive and

light exposure. Hydrogen peroxide is often used for this

popular for cold-water pools, but not suitable for hot

purpose as it is relatively safe in low concentrations, is

pools and spas because it will promote scaling on heat

nonflammable, and produces oxygen and water as end

exchangers and piping. Chlorine levels can be rapidly

products. For the ultraviolet light plus hydrogen peroxide

reduced with high use and regular checks should be made

system to be effective, it must operate 24 hours a day.

to ensure maintenance of disinfection. Some adjustment

Ultraviolet light disinfection is not pH dependent, but

of pH is required for most forms of chlorine disinfection.

the addition of hydrogen peroxide results in slightly acidic

When chlorine gas is used, a fairly high alkalinity needs

conditions [5].

to be maintained to remove the acid formed during

dosing [5]. Sodium hypochlorite is a liquid chlorine, and

Silver-copper Ionization—Sanitizing can be

has a pH of 13, causing a slight increase in the pH of the

accomplished by using an ionizing unit that introduces

pool water, which should be adjusted with an acidic

silver and copper ions into the water by electrolysis, or by

mixture. The sun’s rays will degrade sodium hypochlorite.

passing an electric current through a silver and copper

Chlorinated isocyanate is available in three forms-

electrode. The limiting factors in using this system in the

granular, tablet, and stick. The granular form contains

pool and spa are cost, slow bactericidal action, and

55%-62% available chlorine and the stick and tablet

potentially high contaminant levels caused by bather

form contain 89% available chlorine [6].

loads. Also, black spots can form on pool surfaces if the

proper parameters of water chemistry are not maintained.

Bromine—Bromine needs to be used at levels twice those

An approved chemical disinfectant must be used with an

of chlorine to achieve similar disinfection. Bromine is

ionizing unit [6].

available as the sodium or potassium salts. In the presence

of ammonia, bromine rapidly forms relatively unstable

The effective use of halogen disinfectants is based on the

ammonia bromamines that possess disinfection

pH, hardness, and alkalinity of the water. Improper pH,

efficiencies comparable to that of free bromine. It is also

hardness, and alkalinity levels in the pool can render high

unnecessary to destroy ammonia bromamines because

levels of disinfectant useless in killing disease-causing

they do not produce irritating odors [5].

organisms. Table 14.1 summarizes water-quality problems

that affect pools and suggests corrective actions.

Iodine—Potassium iodide is a white, crystal chemical.

This chemical needs an oxidizer, such as hypochlorite, to

Effect of pH

react with organic debris and bacteria. Iodine does not

The ideal pH to avoid eye irritation is 7.3. Bacteria- or

react with ammonia, hair, or bathing suits, or cause eye

algae-killing effectiveness is improved with an even lower

irritation, but it can react with metals, producing greenish-

pH. National standards typically recommend a range of

colored pool water [6].

7.2 to 7.6, which is cost-effective. Table 14.2

demonstrates the loss of disinfection as pH increases:

Ozone—Ozone is a very powerful oxidant and is effective

against viruses. It can only be generated at the point of

Chlorine Disinfectants

use and commercial generation units are safe for use.

The options for selecting the form of chlorine disinfectant

Ozone dosing is only practical where there is water

to use in pools are quite varied, and the choices are

circulating off-pool because adequate ozone-water mixing

complex. Table 14.3 gives the properties of each form.

is essential for maximum oxidation. Ozone generators

Gas chlorine costs the least, and the relative cost of each

may be of the ultraviolet lamp or corona discharge type.

form of chlorine increases as you move right across the

The ultraviolet lamp efficiency reduces with time and the

table. The cost of the disinfectant tends to be less the

lamp and associated activated charcoal filter will need

higher the concentration of available chlorine. The safety

replacement [5].

issues are more complex than they might appear. The

hazards of gas chlorine are well known. The solid forms of

Ultraviolet Light—Ultraviolet light, like ozone, is

chlorine, such as calcium hypochlorite, are quite reactive.

sometimes used for off-pool water disinfection.

When exposed to organic compounds, they can generate

Ultraviolet light has no effect on pH or color and has

a great deal of heat and are potentially explosive. Because

little effect on the chemical composition of the water.

solid chlorine seems inert to the untrained worker, it is

However, color, turbidity, and chemical composition of

often stored beside motor oil or gasoline or left in where

14-6

Residential Swimming Pools and Spas

Table 14.2. pH Effect on Chlorine Disinfection [7]

Table 14.3. Chlorine Use in Swimming Pools

moisture can start a chemical reaction. Even a pencil with

HOCl + NHCl2 = H2O + NCl3

a graphite core that drops from a shirt pocket into a

Hypochlorous Acid + Dichloramine = Water +

container of calcium hypochlorite could result in a

Nitrogen Trichloride

chemical reaction leading to a fire that would release free

chlorine gas [7].

Tables 14.1-14.4 serve as a quick problem-solving

reference for the home pool owner and operator. The

The following chemical reactions produce chlorine by-

CDC Web site (www.cdc.gov/healthyswimming) provides

products that reduce the effectiveness of chlorine and

a great deal of useful information for both the inspector

cause most eye irritation.

and the homeowner.

Cl2 + H2O = HCl + HOCl

Pool Water Hardness and Alkalinity

Chlorine + Water = Hydrochloric Acid +

The ideal range of water hardness for a plaster pool is

Hypochlorous Acid

200 to 275 ppm. The ideal range for a vinyl, painted, or

fiberglass surface is 175 to 225 ppm. Excess hardness causes

HOCl + NH3 = H2O + NH2Cl

scaling, discoloration, and filter inefficiency. Less than

Hypochlorous Acid + Ammonia = Water +

recommended hardness results in corrosion of most

Monochloramine

contact surfaces.

HOCl + NH2Cl = H2O + NHCl2

Alkalinity should be 80 to 120 ppm. High alkaline levels cause

Hypochlorous Acid + Monochloramine = Water +

scale and high chlorine demand. Low levels cause unstable

Dichloramine

pH. Sodium bicarbonate will raise the alkalinity level. The

pool water will be cloudy if alkalinity is over 200 ppm.

14-8

Residential Swimming Pools and Spas

Erosion and Flow-through Disinfectant Feeders

US Environmental Protection Agency.

These feeders work by the action of water moving around

LT1ESWTR Disinfection profiling and

a solid cake of chlorine and eroding the cake. The feeders

benchmarking: technical guidance manual.

work quite well for smaller pools, but require

Washington, DC: US Environmental Protection

considerable care and maintenance. The variables that

Agency; 2003. Available from URL:

affect the effectiveness of erosion feeders are

http://www.epa.gov/safewater/mdbp/pdf/

profile/lt1profiling.pdf.

1. solubility of the chlorine cake or tablet;

Centers for Disease Control and Prevention.

2. surface area of the cake or tablet;

Healthy swimming. Atlanta: US Department of

Health and Human Services; no date. Available

3. amount of water flowing around the cake or

from URL:

tablet;

http://www.cdc.gov/healthyswimming/.

4. concentration of chlorine in the cake or

tablet; and

Centers for Disease Control and Prevention. Fecal

accidents response recommendations for aquatics

5. number of cakes or tablets in the feeder.

staff. Atlanta: US Department of Health and

Human Services; no date. Available from URL:

Note: For safety reasons, the disinfectant cake must not

http://www.cdc.gov/healthyswimming/fecalacc.htm.

be accessible.

Broadbent C. Guidance on water quality for

Spas and Hot Tubs

heated spas. Rundle Mall, South Australia,

Hot tubs (large tubs filled with hot water for one or more

Australia: Public Environmental Health Service;

people) or spas (a tub with aerating or swirling water) are

1996. Available from URL:

used for pleasure and are increasingly being

http://www.dh.sa.gov.au/pehs/publications/

recommended for therapy. The complexity of these

monograph-heated-spas.pdf.

devices increases with each new model manufactured.

Newer models often have both ozone and ultraviolet light

Michigan State University Pesticide Education

emitters for enhanced disinfection (see Disinfectants

Program. Swimming pool pest management:

section earlier in this chapter). However, the environment

category 5A, a training guide for commercial

of the spa and hot tub, if not cleaned and operated

pesticide applicators and swimming pool

correctly, can become a culture medium for

operators. Chapter 3: pool disinfectants and pH.

microorganisms. Because the warm water is at the ideal

East Lansing, MI: Michigan State University; no

temperature for growth of microorganisms, good

date. Available from URL:

disinfection is critical. Table 14.5 provides suggested hot

http://www.pested.msu.edu/BullSlideNews/

tub and spa operating parameters. It is essential that all

bulletins/pdf/2621/E2621chap3.pdf.

equipment works properly and that the units are cleaned

and disinfected on a routine basis. Monitoring the water

National Swimming Pool Foundation. Certified

temperature is very important and, depending on the

pool-spa operator handbook, 2004. Colorado

health of the user, can be a matter of life and death. Time

Springs, CO: National Swimming Pool

in the heated water should be limited, and the

Foundation; 2004. Available from URL:

temperature for pregnant users should be below 103°F

http://nspf.org.

(39°C) to protect the unborn baby.

Additional Sources of Information

References

American Academy of Pediatrics. Available from URL:

1. Lee HL, Levy DA, Craun GF, Beach MJ,

www.aap.org.

Calderon RL. Surveillance for waterborne-disease

outbreaks—United States, 1999-2000. MMWR

American National Standards Institute. Available from

2002; 51(SS08):1-28. Available from URL:

URL: http://www.ansi.org.

http://www.cdc.gov/mmwr/preview/mmwrhtml/

ss5108a1.htm.

American Red Cross. Available from URL:

www.redcross.org.

14-10

Residential Swimming Pools and Spas