Chapter 13—Energy Efficiency

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

Energy Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

R-values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1

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

Figure 13.1. Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Figure 13.2. Potential Effects of Radiant Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4

Figure 13.3. Common Floor Insulation Flaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

Figure 13.4. Insulation Cavity Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-6

Figure 13.5. Solar Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

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

Healthy Housing Reference Manual 1

Contents
“Engineering is the science of economy, of conserving the

energy, kinetic and potential, provided and stored up by

nature for the use of man. It is the business of engineering to

utilize this energy to the best advantage, so that there may

be the least possible waste.”

William A. Smith

1908

Introduction

Using energy efficiently can reduce the cost of heating,

ventilating, and air-conditioning, which account for a

significant part of the overall cost of housing. Energy

costs recur month-to-month and are hard to reduce after

a home has been designed and built. The development of

an energy-efficient home or building must be thought

through using a systems approach. Planning for energy

efficiency involves considering where the air is coming

from, how it is treated, and where it is desired in the

home. Improper use or installation of sealing and

insulating materials may lead to moisture saturation or

retention, encouraging the growth of mold, bacteria, and

viruses. In addition, toxic chemicals may be created or

contained within the living environment. These building

errors may result in major health hazards. The major

issues that must be balanced in using a systems approach

to energy efficiency are energy cost and availability, longterm affordability and sustainability, comfort and

efficiency, and health and safety. 

Energy Systems

Making sound decisions in designing, constructing, or

updating dwellings will ensure not only greater use and

enjoyment of the space, but also can significantly lower

energy bills and help residents avoid adverse health

effects. Systematic planning for energy efficiency also can

assist prospective homeowners in qualifying for

mortgages because lower fuel bills translate into lower

total housing and utility payments. Some banks and

credit unions take this into account when qualifying

prospective homeowners for mortgages. “Energyefficient” mortgages provide buyers with special benefits

when purchasing an energy-efficient home.

Energy use and efficiency should be addressed in the

context of selection of fuel types and appliances, location

of the equipment, equipment sizing and backup systems,

and programmed use when making decisions on space

heating, water heating, space cooling, window glazing,

and lighting. Usage variables, such as taking excessively

long showers, turning off lights when leaving rooms, or

using appliances at full or near-full capacity, may increase

or decrease energy use, depending on occupancy. Many

of these demands can be optimized in the design stage of

housing for new construction. However, when

remodeling dwellings, making modifications to improve

energy efficiency is often difficult. Preconstruction

consultations with architects and energy specialists can

produce tradeoffs that retain the aesthetics and special

aspects of a dwelling, while making appropriate

investments in energy efficiency. 

A price is paid for poor design and lack of proper

insulation of dwellings, both in dollars for utility bills

and in comfort of the occupants. The layout of rooms

and overall tightness of a house in terms of air exchange

affect energy requirements. In addition, home occupants

and owners often are called on to make relatively minor

decisions affecting total energy consumption, such as

selecting lighting fixtures and bulbs and selecting settings

for thermostats. Buying energy-efficient appliances can

save energy, but the largest reduction in energy use can

be derived from major decisions, such as considering the

R-value of roof systems, insulation, and windows.

R-values

Thermal resistance (a material’s resistance to heat flow) is

rated by R-value. Higher R values mean greater

insulating power, which means greater household energy

savings and commensurate cost savings. Table 13.1 is a

guideline for choosing R-values that are right for a

particular home based on the climate, household heating

system, and area in which it is located.

Another way of understanding R-value is to see it as the

resistance to heat losses from a warmer inside

temperature to the outside temperature through a

material or building envelope (wall, ceiling or roof

assembly, or window). Total heat loss is a function of the

thermal conductivity of materials, area, time, and

construction in a house.

The R-value of thermal insulation depends on the type

of material, its thickness, and its density. In calculating

the R-value of a multilayered installation, the R-values of

the individual layers are added. Installing more insulation

increases R-value and the resistance to heat flow. 

The effectiveness of an insulated wall or ceiling also

Chapter 13: Energy Efficiency

Healthy Housing Reference Manual 13-1
depends on how and where the insulation is installed. For

example, insulation that is compressed will not provide its

full rated R-value. Also, the overall R-value of a wall or

ceiling will be somewhat different from the R-value of the

insulation itself because some heat flows around the

insulation through the studs and joists. That is, the

overall R-value of a wall with insulation between wood

studs is less than the R-value of the insulation itself

because the wood provides a thermal short-circuit around

the insulation. The short-circuiting through metal

framing is much greater than that through wood-framed

walls; sometimes the metal wall’s overall R-value can be as

low as half the insulation’s R-value. With careful design,

this short-circuiting can be reduced.

Roofs

Roofs are composite structures, with composite R-values.

The total R-value for the roof components shown in

Figure 13.1 is 14.54 (Table 13.2). In general, a composite

structure with a composite R-value of more than R-38

provides a substantial barrier to heat loss. Of course, in

the winter the outside air temperature would vary

significantly between locations such as Pensacola, Florida,

and Fairbanks, Alaska, and would affect the cost13-2 Energy Efficiency

Table 13.1. Cost-effective Insulation R-values for Existing Homes [a;1]
effectiveness of additional insulation and construction

using various roofing components (Table 13.2).

The location of a house is usually a fixed variable in

calculating R-values once the lot is purchased. However,

the homeowner should consider the value of additional

insulation by comparing its cost with the savings resulting

from the increase in energy efficiency. Roof construction,

including components such as ridge vents and insulating

materials, is quite important and is often one of the more

cost-effective ways to lower energy costs. 

Ridge Vents

Ridge vents are important to roofs for at least three

reasons. First, ridge vents help lower the temperature in

the roof structure and, consequently, in the attic and in

the habitable space below. Second, ridge vents and

rotating turbine vents help prolong the life of the roofing

materials, particularly asphalt shingles and plywood

sheathing. Third, ridge vents assist in air circulation and

help avoid problems with excessive moisture. 

Fan-powered Attic Ventilation

Attic ventilators are small fans that remove hot air and

reduce attic temperature. Adequate inlet vents are

important. Typically these vents are located under the

eaves of the house. The fan should be located near the

peak of the roof for best performance.

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

comfort and cuts electricity or natural gas costs for

heating and cooling. For instance, the use of R-19

insulation in houses in Hawaii [3] could have the

following results: 

• Reduce indoor air temperature by 4°F (-16°C) in

the afternoon. 

• Lower the ceiling temperature, perhaps by more

than 15°F (-9.4°C). Insulation [radiant barrier]

can reduce ceiling temperatures from 101°F

(38°C) in bright sun on Oahu to 83°F (28°C).

(Figure 13.2).

• Reduce or eliminate the need for an airconditioner. 

Energy savings, of course, will vary depending on energy

prices. The payback afforded by additional insulation or

investment in energy conservation measures is the average

amount of time it will require for the initial capital cost

to be recovered as a result of the savings in energy bills. A

payback of 3 to 5 years might be economic, because the

average homeowner stays in a home that long. However,

payback criteria can vary by individual, and renters, for

example, often face the dilemma of not wanting to make

improvements for which they may not be able to fully

realize the benefits. Described below are a few insulation

alternatives.

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

Healthy Housing Reference Manual 13-3

Figure 13.1. Roof Components [2]

Table 13.2. Potential Effects of Radiant Barriers [3]
insulation may be available. For the best performance,

insulation should be 5 to 6 inches thick. It can be installed

in attics of new and existing homes. It is typically the best

choice for framed ceilings in new homes, but can be costly

to install in existing framed ceilings. It is very important

that this type of insulation be treated for fire resistance.

Foamboard (R-10, 1.5 to 2 inches) provides more insulation

per inch than does cellulose or fiberglass, but is also more

expensive. It is best where other insulation cannot be

used, such as open-beam ceilings. It is applicable for new

construction or when roofing is replaced on an existing

home. Two common materials are polystyrene and

polyisocyanurate. Polystyrene is better in moist conditions,

and polyisocyanurate has a higher R-value per inch

(millimeter). However, some of these insulations present

serious fire spread hazards. They should be evaluated to

ensure that they are covered with fire-retardant materials

and meet local fire and building codes.

Radiant barrier insulation is a reflective foil sheet

installed under the roof deck like regular roof sheathing.

The effectiveness of a radiant barrier (Figure 13.2)

depends on its emissivity (the relative power of the surface

to emit heat by radiation). In general, the shinier the foil

the better. Radiant barrier insulation cuts the amount of

heat radiated from the hot roof to the ceiling below. It

may be draped over the rafters before the roof is installed

or stapled to the underside of the rafters. The shiny side

should face downward for best performance. Some

manufacturers claim that the radiant barrier prevents up to

97% of the sun’s heat from entering the attic.

Wall Insulation

As shown in Table 13.1, it makes sense to insulate to high

R-values in the ceiling. Insulation in walls should range

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

pump, to electric resistance, will also affect the payback of

additional wall insulation due to variation in energy fuel

prices. For regions identified as “cold,” careful attention

should be made in selecting energy fuel type; in

particular, a heat pump may not be a practical option.

A homeowner exploring designs and construction methods

should examine the value of using structural insulated

panels. The incorporation of high levels of insulation

directly from the factory on building wall and ceiling

components makes them outstanding barriers to heat and

moisture. These integrated systems, if appropriately used,

can save substantial amounts of energy when compared

with traditional stick-built systems using 2×4 or 2×6

lumber. Also, building energy-efficient features (as well as

electrical, plumbing, and other elements) directly into the

building envelope at the factory can result in labor cost

savings over the more traditional methods of construction.

Floor Insulation

Warm air expands and rises above surrounding cooler air.

This process of heat transfer is called convection. Warm

air, which is lighter, rises and, as it cools, falls, creating a

convection current of air. The two other processes of heat

transfer are conduction (kinetic energy transferred from

particle to particle, such as in a water- or electrically

heated floor) and radiation (radiant energy emitted in the

form of waves or particles such as in a fireplace or hot

glowing heating element). Floor insulation limits all three

modes of heat loss. A warmer floor reduces the temperature

difference that drives convection. Floor insulation also

directly impedes conduction and radiation to the colder

air below the floor.

Batt Insulation 

The advantage of floor insulation lies in adding extra

R-value without a significant increase in cost. It is cheaper to

13-4 Energy Efficiency

Figure 13.2. Potential Effects of Radiant Barriers [3]
put more insulation under the floor than to add foam

sheathing or change the type of wall construction to

accommodate greater insulation levels. 

Like walls, floor cavities should be completely filled with

insulation-without gaps, missing insulation, or cavity

voids. Floor insulation must contact the subfloor and

both joists. In many cases, it is worth the extra cost to

buy enough insulation to fill the entire cavity.

The amount of floor insulation required by some codes

can be less than the space available. For example, an R-19

fiberglass batt is 61⁄4 inches thick. A floor framed with

2×8s is about 71⁄2 inches deep, while a 2×10 floor is

91⁄2 inches deep. A builder following a code’s minimum

insulation level will leave extra space that will allow for

greater heat loss. To avoid this situation, the batt must be

pushed up into the cavity. With the proper support, this

can be done. Springy metal rods are commonly used to

hold insulation up in the top of the floor cavity. Another

viable option is the use of plastic straps. Figure 13.3

shows batt insulation improperly applied to the floor

above a crawl space or a basement.

The thickness of typical fiberglass batts can assist the

designer and the builder in creating a floor system that

works for the occupants. Table 13.3 shows a list of R-values,

along with the associated batt thickness. Individual

brands can vary by as much as 1 inch. 

Cavity Fill 

According to Oikos, a commercial Web site devoted to

serving professionals whose work promotes sustainable

design and construction, “Buying a thicker batt may be a

better option than trying to lift a thinner batt into the

proper position. Material costs will climb slightly but labor

should be the same. Attaching the insulation support to the

bottom of the floor joist will be easier. It could also lead to a

higher quality job because there is less chance for

compression or gaps” (Figure 13.4) [4]. 

In some areas, it’s common to hang plastic mesh over

floor joists. Installers drop the insulation onto the mesh

before the subfloor is

installed. However,

hanging the mesh

creates sagging bellies.

Insulation compresses

near the framing and

sags in the middle. Mesh

should be attached to the

bottom of the floor

framing [4]. 

Each stage of increased

floor insulation, from

R-19 to R-30 or R-30 to

R-38, can save energy over

the life of the house. This energy translates into energy

savings that are multiples of the initial installation costs.

Floor insulation will generate the greatest savings in

colder climates; in moderate climates, the target

insulation level should depend on economics.

Blow-In Insulation

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

walls and ceilings. That said, heat loss follows the path of

least resistance; therefore, doors should be selected that

Healthy Housing Reference Manual 13-5

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.

Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc.,

publisher of Oikos.com.

Table 13.3. Floor Insulation [5]
are functional and add to the energy-efficiency of the

house. Doors usually have lower R-values than the

surrounding wall.

Storm doors can add R-1 to R-2 to the existing door’s Rvalue. They are a valuable addition to doors that are

frequently used and those that are exposed to cold winds,

snow, and other weather. Screens allow natural breezes to

circulate air from outside, rather than totally relying on

air-conditioning, which can be energy intensive.

When considering replacement doors, select insulated,

metal foam-core doors. Besides insulation, metal doors

provide good security, seal more tightly, tend to warp less.

Metal doors also are more soundproof than conventional

wood doors. 

Sliding Glass Doors

Although sliding glass doors have aesthetic appeal, they

have very low R-values and hence are minimally energy

efficient. To improve the energy efficiency of existing

sliding glass doors, the homeowner should ensure that

they seal tightly and are properly weather-stripped.

Additionally, heavy insulated drapes with weights, which

impede the airflow, can cut down on heat loss through

sliding glass doors.

13-6 Energy Efficiency

Figure 13.4a. Insulation Cavity Fill [4]. 

Lath provides a sturdy support for insulation.

Figure 13.4b. Insulation Cavity Fill [4]. 

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]. 

Mesh should be attached to the bottom of the framing. Draping the mesh over

the joists leads to compression that reduces insulating value.

Figure 13.4d. Insulation Cavity Fill [4]. 

Polypropylene twine resists rot, mildew, rodents, and other dangers. It is to be

stapled every 12 to 18 inches.

Source: Reprinted from Energy Source Builder 38 with permission of Iris Communications, Inc., publisher of Oikos.com.
Door Installation

Doors must be installed as recommended by the

manufacturer. Care must be taken to be sure that doors

are installed in a manner that does not trap moisture or

allow unintended introduction of air. Numerous types of

sealing materials are available that range from foam to

plastic, to metal flanging and magnetic strips.

Hot Water Systems

The hot water tank can be insulated to make it more

efficient, unless the heat loss is used within the space

where it is located. Special insulation is available for this

type of appliance, and insulating it will reduce the energy

required to deliver the hot water needed by the occupants

of the dwelling. Of course, any pipe that is subject to

extreme temperatures also should be insulated to decrease

heat loss.

Windows

Windows by nature are transparent. They allow occupants

of a dwelling to see outside and bring in sunlight and

heat from the sun. They make space more pleasant and

often provide lighting for tasks undertaken in the space.

Especially in the winter, these desirable characteristics

offset the heat loss. Heat gain in the summer through

windows can be undesirable.

Rather than give them up, it is important to use windows

prudently and to keep energy considerations in mind in

their design and their insulating characteristics (air, glass,

plastic, or gas filler). Good design takes advantage of day

lighting. Weather-stripping and sealing leaks around

windows can enhance comfort and energy savings. Energy

Star windows are highly recommended. Housekeeping

measures can improve the efficiency of retaining heat.

Heat loss follows the path of least resistance: caulking,

weather-stripped framing, and films can help. These

measures are relatively labor intensive, low to very low in

cost, and can be quite satisfying to the homeowner if

accomplished correctly. On the other hand, it is not easy

finding the perfect materials or even replacement parts for

old windows.

When working with older windows, remember that there

is the risk for leaded paint and the dispersion of toxic lead

dust into the work area. Please refer to the lead section of

Chapter 5, Indoor Air Pollutants and Toxic Materials.

Caulking and Weather-Stripping 

According to the U.S. Department of Energy, caulking

and weather-stripping have substantial housekeeping 

benefits in preventing energy loss or unwanted heat gain.

Caulking

Caulks are airtight compounds (usually latex or silicone)

that fill cracks and holes. Before applying new caulk, old

caulk or paint residue remaining around a window should

be removed using a putty knife, stiff brush, or special

solvent. After old caulk is removed, new caulk can then

be applied to all joints in the window frame and the joint

between the frame and the wall. The best time to apply

caulk is during dry weather when the outdoor

temperature is above 45°F (7.2°C). Low humidity is

important during application to prevent cracks from

swelling with moisture. Warm temperatures are also

necessary so the caulk will set properly and adhere to the

surface [5].

Weather-stripping

Weather-stripped frames are narrow pieces of metal, vinyl,

rubber, felt, or foam that seal the contact area between

the fixed and movable sections of a window joint. They

should be applied between the sash and the frame, but

should not interfere with the operation of the window [6].

Replacing Window Frames 

The heat-loss characteristics and the air tightness of a window

vary with the type and quality of the window frame. The

types of available window frames are fixed-pane,

casement, double- and single-hung, horizontal sliding,

hopper, and awning. Each type varies in energy efficiency. 

Correctly installed fixed-pane windows are the most

airtight and inexpensive choice, but are not suited to

places that require ventilation. The air infiltration

properties of casement windows (which open sideways

with hand cranks), awning windows (which are similar to

casement windows but have hinges at the top), and

hopper windows (inverted awning windows with hinges

at the bottom) are moderate. Double-hung windows,

which have top and bottom sashes (the part of the

window that can slide), tend to be leaky. The advantage

of the single-hung window over the double-hung is that it

tends to restrict air leakage because there is only one

moving part. Horizontal sliding windows, though suitable

for small, narrow spaces, provide minimal ventilation and

are the least airtight. 

In buildings with large older windows, there are often

weight cavity areas that hide counter balances that make

it easy to raise and lower heavy windows. These areas

should be insulated to reduce energy loss.

Healthy Housing Reference Manual 13-7
Tinted Windows

Another way to conserve energy is the installation of

tinted windows. Window tinting can be installed that will

both conserve energy and also prevent damaging ultraviolet

light from entering the room and potentially fading wood

surfaces, fabrics, and carpeting. Low-emissivity coatings,

called low-e coatings, are also available. These coatings are

designed for specific geographic regions. 

Reducing Heat Loss and Condensation 

The energy efficiency of windows is measured in terms of

their U-values (measure of the conductance of heat) or

their R-values. Besides a few highly energy-efficient

exceptions, window R-values range from 0.9 to 3.0.

When comparing different windows, it is advisable to

focus on the following guidance for R- and U-values:

• R- and U-values are based on standards set by the

American Society of Heating, Refrigerating, and

Air-Conditioning Engineers [7].

• R- and U-values are calculated for the entire

window, which includes the frame.

• R- and U-values represent the same style and size

of windows.

The R-value of a window in an actual house is affected by

the type of glazing material, the number of layers of glass,

the amount of space between layers and the nature of the

gas filling them, the heat-conducting properties of the frame

and spacer materials, and the airtightness associated with

manufacturing. 

For windows, rating and approval by the National Fenestration

Rating Council or equivalent rating and approval is

strongly recommended [8].

Please refer to the window section of Chapter 6, Housing

Structure. 

Glazing

Glazing refers to cutting and fitting windowpanes into

frames. Glass has been traditionally the material of choice

for windowpanes, but that is changing. Several new

materials are available that can increase the energy

efficiency of windows. These include the following:

• Low-emissivity (low-e) glass uses a surface coating

to minimize transmission of heat through the

window by reflecting 40% to 70% of incident

heat while letting full light pass through the pane.

• Heat-absorbing glass is specially tinted to absorb

approximately 45% of the incoming solar energy;

some of this energy passes through the pane.

• Reflective glass has a reflective film that reduces heat

gain by reflecting most of the incident solar radiation.

• Plastic glazing materials such as acrylic,

polycarbonate, polyester, polyvinyl fluoride, and

polyethylene are stronger, lighter, cheaper, and

easier to cut than glass. However, they are less

durable and tend to be affected by the weather

more than glass is. 

• Storm windows can improve the energy efficiency

of single-pane windows. The simplest example of

storm windows would be plastic film, available in

prepackaged kits, taped to the inside of the

window frame. Because this can affect visibility

and be easily damaged, a better choice would be

to attach rigid or semirigid plastic sheets such as

plexiglass, acrylic, polycarbonate, or fiberreinforced polyester directly to the window frame

or mounting it in channels around the frame on

the outside of the building. Care should be taken

in installation to avoid ripples or blemishes that

will affect visibility.

Layering

The insulating capacity of single-pane windows is minimal,

around R-1. Multiple layers of glass can be used to increase

the energy efficiency of windows. Double- or triple-pane

windows have air-filled or gas-filled spaces, coupled with

multiple panes that resist heat flow. The space between

the panes is critical because the air spaces that are too

wide (more than 5/8 inch) or too narrow (less than 1⁄2 inch)

allow excessive heat transfer. Modern windows use inert

gases, such as argon and krypton, to fill the spaces

between panes because these gases are much more

resistant to heat flow than air is. These gas-filled windows

are more expensive than regular double-pane windows. 

• Frame and spacer materials may be aluminum,

wood, vinyl, fiberglass, or a combination of these

materials, such as vinyl- or aluminum-clad wood. 

• Aluminum frames are strong and are ideal for

customized window design, but they conduct heat

and are prone to condensation. The deterioration

of these frames can be avoided by anodizing or

coating. Their thermal resistance can be boosted 

13-8 Energy Efficiency
using continuous strips of plastic between the

interior and exterior of the frame. 

• Wood frames are superior to aluminum frames in

having higher R-values, tolerance to temperature

extremes, and resistance to condensation. On the

other hand, wood frames require considerable

maintenance in the form of painting or staining.

Improper maintenance can lead to rot or warping.

• Vinyl window frames made from polyvinyl

chloride are available in a wide range of styles and

shapes, can be easily customized, have moderate

R-values, and can be competitively priced. Large

windows made of vinyl frames are reinforced

using aluminum or steel bars. Vinyl windows

should be selected only after consideration of the

concerns surrounding the use of vinyl materials

and their off-gassing characteristics.

• Fiberglass frames have the highest R-values and

are not given to warping, shrinking, swelling,

rotting, or corroding. Fiberglass is not weatherresistant, so it should also be painted. Some

fiberglass frames are hollow; others are filled with

fiberglass insulation.

• Spacers separating multiple windowpanes in a

window use aluminum to separate glass in

multipane windows, but it conducts heat. In

addition, in cold weather, the thermal resistance

around the edge of such a window is lower than

that in the center, allowing heat to escape and

condensation to occur along the edges. 

• Polyvinyl chloride foam separators placed along

the edges of the frame reduce heat loss and

condensation. Window manufacturers use foam

separators, nylon spacers, and insulation materials

such as polystyrene and rock wool insulation

between the glass panes inside windows.

Other Options

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.

Solar Energy

Solar energy is a form of renewable energy available to

homeowners for heating, cooling, and lighting. The more

energy-efficient new structures are designed to store solar

energy. Remodeled structures may be retrofitted to increase

energy efficiency by improving insulation characteristics,

improving airflow and airtightness of the structure, and

enhancing the ability to use solar energy. Solar energy

systems are active and passive. Whereas active solar systems use

some type of mechanical power to collect, store, and

distribute the sun’s energy, passive systems use the

materials and design elements in the structure itself. 

Active Solar Systems

Active solar systems use devices to collect, convert, and

deliver solar energy. Solar collectors on roofs or other

south-facing surfaces can be used to heat water and air

and generate electricity. Active solar systems can be

installed in new or existing buildings and periodically

need to be inspected and maintained. Active solar energy

equipment consists of collectors, a storage tank, piping or

ductwork, fans, motors, and other hardware. Flat panel

collectors (Figure 13.5) can be placed on the roof or on

walls. Typically, the collector will be a sandwich of one or

two sheets of glass or plastic and another air space above a

metal absorber plate, which is painted black to enhance

heat absorption. After collection, when the sun’s energy is

converted to heat, a transfer is made to a liquid storage

tank. The heated liquid travels through coils in the hot

water tank, and the heat is transferred to the water and

perhaps the heating system. Most hot water systems use a

liquid collector system because it is more efficient and less

costly than an air-type system.

In the southwest United States, solar roof ponds have

become popular for solar cooling. Evaporative cooling

systems depend on water vaporization to lower the

temperature of the air. These have been shown to be more

effective in dry climates than in areas with extremely high

relative humidity.

In certain climates, like those in the Hawaiian Islands,

using solar energy is cost-effective for providing hot water.

Figure 13.5. Solar Panels

Healthy Housing Reference Manual 13-9
Some builders even include it as a standard feature in

their homes. The total cost to the homeowner of solar

energy systems consists of the capital, operational, and

maintenance costs. The real cost of capital may be

lowered by the availability of tax credits offered at the

federal (to lower federal income taxes) and state levels. 

Homeowners and builders can benefit from tax credits

because they lower the total upfront investment cost of

installing active solar systems. This is the major portion of

the total cost of using solar energy, because operation and

maintenance costs are small in comparison to initial

system costs.

Passive Solar Systems

Buildings designed to use passive solar energy have

features incorporated into their design that absorb and

slowly release the sun’s heat. In cold climates, the design

allows the light and heat of the sun to be stored in the

structure, while insulating against the cold. In warm

climates, the best effect is achieved by admitting light

while rejecting heat. A building using passive solar

systems may have the following features in the floor plan:

• Large south-facing windows

• Small windows in other directions, particularly on

the north side of the structure

• Designs that allow daylight and solar heat to

permeate the main living areas

• Special glass to block ultraviolet radiation

• Building materials that absorb and slowly

reradiate the solar heat

• Structural features such as overhangs, baffles, and

summer shading to eliminate summer

overheating.

Passive design can be a direct-gain system when the sun

shines directly into the building, thereby heating it and

storing this heat in the building materials (concrete, stone

floor slabs, and masonry partitions). Alternatively, it may

be an indirect gain system where the thermal mass is

located between the sun and the living space. Isolated

gain is yet another type of system that is separated from

the main living area (such as a sunroom or a solar

greenhouse), with convective loops for space conditioning

into the living space.

Energy Star is a program supported and promoted by the

U.S. Environmental Protection Agency (EPA) that helps

individuals protect the environment through superior

energy efficiency. For the individual in his or her home,

energy-efficient choices can save families about one third

on their energy bill, with similar savings of greenhouse

gas emissions, without sacrificing features, style, or

comfort. When replacing household products, look for

ones that have earned the Energy Star; these products

meet strict energy-efficiency guidelines set by EPA and

the U.S. Department of Energy. When looking for a new

home, look for one that has earned the Energy Star

approval. If you are planning to make larger

improvements to your home, EPA offers tools and

resources to help you plan and undertake projects to

reduce your energy bills and improve home comfort [9].

In 2004 alone, Americans, with the help of Energy Star,

saved enough energy to power 24 million homes and

avoid greenhouse gas emissions equivalent to those from

20 million cars-all while saving $10 billion.

Conducting an Energy Audit

Energy audits can help identify areas where energy

investments can be made, thereby reducing energy used in

lighting, heating, cooling, or meeting other demands of

housing occupants. An inspection can evaluate the

worthiness or compliance with codes of energy-saving

measures, including accepted or written standards. For

example, if a new addition requires the equivalent of R-19

insulation in the ceilings, this can be validated in the

inspection process. Whereas an audit is generally

informational, an inspection should validate that

materials and workmanship have yielded a structure that

protects the occupants from the elements, such as rain,

snow, wind, cold, and heat. Potentially hazardous

situations within a structure should be evaluated in an

inspection. The overall goal of a housing inspection in the

case of energy efficiency is to identify potential hazardous

conditions and help to create conditions under which the

health and welfare of the occupants can be enhanced,

rather than put at risk.

The housing inspector should be aware that there is

variation (sometimes quite significant differences) in

heating degree days or cooling loads and in relative

humidity conditions within given regions. Local and

regional topography, as well as site conditions, can affect

temperatures and moisture.

Numerous Web sites listed in this chapter’s Additional

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 costeffective conservation measures for given areas of the

United States.

References

1. Lawrence Berkeley National Laboratory. Energy

star insulation project: R-value guidelines.

Berkeley, CA: Lawrence Berkeley National

Laboratory; 2004. Available from URL:

http://enduse.lbl.gov/Projects/Rvalue.html.

2. RoofHelp.com. R-value. Fort Worth, TX:

RoofHelp; 1999. Available from URL:

http://www.roofhelp.com/Rvalue.htm.

3. State of Hawaii, Department of Business,

Economic Development, and Tourism, Energy

Resources and Technology Division. Ceiling

insulation. Honolulu, HI: State of Hawaii,

Department of Business, Economic Development,

and Tourism; no date. Available from

URL:http://www.hawaii.gov/dbedt/

ert/rf_insul.html. 

4. Oikos. Filling a floor with batt insulation. Energy

Source Builder 1995 [Apr]; 38. Available from

URL: http://oikos.com/esb/38/

floorinsulation.html.

5. US Department of Energy. Energy savers: fact

sheets. Washington, DC: US Department of

Energy; no date. Available from URL:

http://www.eere.energy.gov/consumerinfo/

factsheets.html.

6. US Department of Energy. Advances in glazing

materials for windows. Washington, DC: US

Department of Energy; 1994. 

7. American Society of Heating, Refrigerating and

Air-Conditioning Engineers (ASHRAE).

Standards; no date. Atlanta: American Society of

Heating, Refrigerating and Air-Conditioning

Engineers. Available from URL:

http://www.ashrae.org.

8. National Fenestration Rating Council. Search for

energy performance ratings. Silver Spring, MD:

National Fenestration Rating Council; no date.

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

windowshop/surveybegin.aspx.

9. US Environmental Protection Agency. What is

Energy Star? Washington, DC: US Environmental

Protection Agency; no date. Available from URL:

http://www.energystar.gov/

index.cfm?c=about.ab_index.

Additional Sources of Information

Alliance to Save Energy. Save energy at home. Available

from URL: http://www.ase.org/section/

_audience/educators/edsavhome/.

Christian J, Kosnay J. Home Calculating whole wall Rvalues on the Net. Energy Magazine Online,

November/December 1999. 

Energy Information Administration. Available from URL:

http://www.eia.doe.gov.

Environmental Solar Systems. Available from URL:

http://www.environmentalsolarsystems.com/systems/.

Enviro$en$e: Common sense solutions to environmental

problems. Available from URL: http://es.epa.gov/.

Florida Power and Light. Building shell: insulation.

Available from URL: http://www.fpl.com/savings/

energy_advisor/PA_45.html.

Florida Power and Light. Online home energy survey.

Available from URL:

http://www.fpl.com/home/ohes/contents/

online_home_energy_survey.shtml.

Hawaii Department of Business, Economic Development

and Tourism. Ceiling insulation. Available from URL:

http://www.state.hi.us/dbedt/ert/rf_insul.html.

National Association of State Energy Officials. Available

from URL: http://www.naseo.org.

Nexus Energyguide. Available from URL:

http://www.energyguide.com/default.asp.

Oak Ridge National Laboratory Buildings Technology

Center. Available from URL:

http://www.ornl.gov/ORNL/BTC.

Oak Ridge National Laboratory. Whole-wall thermal

calculator performance. Available from URL:

http://www.ornl.gov/roofs+walls/

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