Chapter 13—Energy EfficiencyIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1Energy Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1R-values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-1Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-2

Ridge Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3Fan-powered Attic Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3White Roof Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3

Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3Wall Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4Floor Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5Hot Water Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7

Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7Caulking and Weather-stripping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7Replacing Window Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-7Tinted Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8

Reducing Heat Loss and Condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8Glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8Layering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-8Other Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9Active Solar Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9Passive Solar Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-10

Conducting an Energy Audit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-10References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-11Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-11

Figure 13.1. Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3Figure 13.2. Potential Effects of Radiant Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-4Figure 13.3. Common Floor Insulation Flaws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5Figure 13.4. Insulation Cavity Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-6Figure 13.5. Solar Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-9

Table 13.1. Cost-effective Insulation R-values for Existing Homes . . . . . . . . . . . . . . . . . . . . . .13-2Table 13.2. R-values of Roof Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-3Table 13.3. Floor Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-5

1Healthy Housing Reference Manual

Contents

“Engineering is the science of economy, of conserving theenergy, kinetic and potential, provided and stored up bynature for the use of man. It is the business of engineering toutilize this energy to the best advantage, so that there maybe the least possible waste.”

William A. Smith1908

IntroductionUsing energy efficiently can reduce the cost of heating,ventilating, and air-conditioning, which account for asignificant part of the overall cost of housing. Energycosts recur month-to-month and are hard to reduce aftera home has been designed and built. The development ofan energy-efficient home or building must be thoughtthrough using a systems approach. Planning for energyefficiency involves considering where the air is comingfrom, how it is treated, and where it is desired in thehome. Improper use or installation of sealing andinsulating materials may lead to moisture saturation orretention, encouraging the growth of mold, bacteria, andviruses. In addition, toxic chemicals may be created orcontained within the living environment. These buildingerrors may result in major health hazards. The majorissues that must be balanced in using a systems approachto energy efficiency are energy cost and availability, long-term affordability and sustainability, comfort andefficiency, and health and safety.

Energy SystemsMaking sound decisions in designing, constructing, orupdating dwellings will ensure not only greater use andenjoyment of the space, but also can significantly lowerenergy bills and help residents avoid adverse healtheffects. Systematic planning for energy efficiency also canassist prospective homeowners in qualifying formortgages because lower fuel bills translate into lowertotal housing and utility payments. Some banks andcredit unions take this into account when qualifyingprospective homeowners for mortgages. “Energy-efficient” mortgages provide buyers with special benefitswhen purchasing an energy-efficient home.

Energy use and efficiency should be addressed in thecontext of selection of fuel types and appliances, locationof the equipment, equipment sizing and backup systems,and programmed use when making decisions on spaceheating, water heating, space cooling, window glazing,

and lighting. Usage variables, such as taking excessivelylong showers, turning off lights when leaving rooms, orusing appliances at full or near-full capacity, may increaseor decrease energy use, depending on occupancy. Manyof these demands can be optimized in the design stage ofhousing for new construction. However, whenremodeling dwellings, making modifications to improveenergy efficiency is often difficult. Preconstructionconsultations with architects and energy specialists canproduce tradeoffs that retain the aesthetics and specialaspects of a dwelling, while making appropriateinvestments in energy efficiency.

A price is paid for poor design and lack of properinsulation of dwellings, both in dollars for utility billsand in comfort of the occupants. The layout of roomsand overall tightness of a house in terms of air exchangeaffect energy requirements. In addition, home occupantsand owners often are called on to make relatively minordecisions affecting total energy consumption, such asselecting lighting fixtures and bulbs and selecting settingsfor thermostats. Buying energy-efficient appliances cansave energy, but the largest reduction in energy use canbe derived from major decisions, such as considering theR-value of roof systems, insulation, and windows.

R-valuesThermal resistance (a material’s resistance to heat flow) israted by R-value. Higher R values mean greaterinsulating power, which means greater household energysavings and commensurate cost savings. Table 13.1 is aguideline for choosing R-values that are right for aparticular home based on the climate, household heatingsystem, and area in which it is located.

Another way of understanding R-value is to see it as theresistance to heat losses from a warmer insidetemperature to the outside temperature through amaterial or building envelope (wall, ceiling or roofassembly, or window). Total heat loss is a function of thethermal conductivity of materials, area, time, andconstruction in a house.

The R-value of thermal insulation depends on the typeof material, its thickness, and its density. In calculatingthe R-value of a multilayered installation, the R-values ofthe individual layers are added. Installing more insulationincreases R-value and the resistance to heat flow. The effectiveness of an insulated wall or ceiling also

Chapter 13: Energy Efficiency

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depends on how and where the insulation is installed. Forexample, insulation that is compressed will not provide itsfull rated R-value. Also, the overall R-value of a wall orceiling will be somewhat different from the R-value of theinsulation itself because some heat flows around theinsulation through the studs and joists. That is, theoverall R-value of a wall with insulation between woodstuds is less than the R-value of the insulation itselfbecause the wood provides a thermal short-circuit aroundthe insulation. The short-circuiting through metalframing is much greater than that through wood-framedwalls; 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.

RoofsRoofs are composite structures, with composite R-values.The total R-value for the roof components shown inFigure 13.1 is 14.54 (Table 13.2). In general, a compositestructure with a composite R-value of more than R-38provides a substantial barrier to heat loss. Of course, inthe winter the outside air temperature would varysignificantly between locations such as Pensacola, Florida,and Fairbanks, Alaska, and would affect the cost-

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Table 13.1. Cost-effective Insulation R-values for Existing Homes [a;1]

effectiveness of additional insulation and constructionusing various roofing components (Table 13.2).

The location of a house is usually a fixed variable incalculating R-values once the lot is purchased. However,the homeowner should consider the value of additionalinsulation by comparing its cost with the savings resultingfrom the increase in energy efficiency. Roof construction,including components such as ridge vents and insulatingmaterials, is quite important and is often one of the morecost-effective ways to lower energy costs.

Ridge VentsRidge vents are important to roofs for at least threereasons. First, ridge vents help lower the temperature inthe roof structure and, consequently, in the attic and inthe habitable space below. Second, ridge vents androtating turbine vents help prolong the life of the roofingmaterials, particularly asphalt shingles and plywoodsheathing. Third, ridge vents assist in air circulation andhelp avoid problems with excessive moisture.

Fan-powered Attic VentilationAttic ventilators are small fans that remove hot air andreduce attic temperature. Adequate inlet vents areimportant. Typically these vents are located under theeaves of the house. The fan should be located near thepeak of the roof for best performance.

White Roof SurfaceWhite roof surfaces combined with any of the measureslisted above will improve their performance significantly.The white surface reflects much of the sun’s heat andkeeps the roof much cooler than a typical roof.

InsulationInsulation forms a barrier to the outside elements. It canhelp ensure that occupants are comfortable and that thehome is energy-efficient. Ceiling insulation improvescomfort and cuts electricity or natural gas costs forheating and cooling. For instance, the use of R-19insulation in houses in Hawaii [3] could have thefollowing results:

• Reduce indoor air temperature by 4°F (-16°C) inthe afternoon.

• Lower the ceiling temperature, perhaps by morethan 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 air-conditioner.

Energy savings, of course, will vary depending on energyprices. The payback afforded by additional insulation orinvestment in energy conservation measures is the averageamount of time it will require for the initial capital costto be recovered as a result of the savings in energy bills. Apayback of 3 to 5 years might be economic, because theaverage homeowner stays in a home that long. However,payback criteria can vary by individual, and renters, forexample, often face the dilemma of not wanting to makeimprovements for which they may not be able to fullyrealize the benefits. Described below are a few insulationalternatives.

To achieve maximum effect, the method of installationand type of insulation are of considerable importance.The proper placement of moisture barriers is essential. Ifinsulation becomes moisture-saturated, its resistance toenergy loss is significantly reduced. Barriers to moistureshould be installed toward the living area becausesignificant moisture is generated in the home throughrespiration, cooking, and the combustion of heating fuels.

Cellulose or fiberglass insulation is the most cost-effectiveinsulation. Blown-in cellulose or fiberglass and fiberglassbatts are similar in cost and performance. Recycled cellulose

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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 installedin attics of new and existing homes. It is typically the bestchoice for framed ceilings in new homes, but can be costlyto install in existing framed ceilings. It is very importantthat this type of insulation be treated for fire resistance.

Foamboard (R-10, 1.5 to 2 inches) provides more insulationper inch than does cellulose or fiberglass, but is also moreexpensive. It is best where other insulation cannot beused, such as open-beam ceilings. It is applicable for newconstruction or when roofing is replaced on an existinghome. Two common materials are polystyrene andpolyisocyanurate. Polystyrene is better in moist conditions,and polyisocyanurate has a higher R-value per inch(millimeter). However, some of these insulations presentserious fire spread hazards. They should be evaluated toensure that they are covered with fire-retardant materialsand meet local fire and building codes.

Radiant barrier insulation is a reflective foil sheetinstalled 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 surfaceto emit heat by radiation). In general, the shinier the foilthe better. Radiant barrier insulation cuts the amount ofheat radiated from the hot roof to the ceiling below. Itmay be draped over the rafters before the roof is installedor stapled to the underside of the rafters. The shiny sideshould face downward for best performance. Somemanufacturers claim that the radiant barrier prevents up to97% of the sun’s heat from entering the attic.

Wall InsulationAs shown in Table 13.1, it makes sense to insulate to highR-values in the ceiling. Insulation in walls should range

from R-11 in relatively mild climate zones to R-38 inNew England, the northern Midwest, the Great Lakes,and the Rocky Mountain states of Colorado and Wyoming.Insulation requirements vary within climate zones in thesestates and areas as well (for instance, mountainous areasand areas farther north may have more heating-degreedays). The same logic of installing insulation applies toboth ceilings and walls: the insulation should provide abarrier for heat and moisture transfer and buildup frominside the dwelling, where temperatures will generally bein the 68°F to 72°F (20°C to 22°C) range, comparedwith the much colder or hotter temperatures outside. Thekey to heat loss is the difference in temperatures and thetime that the heat transfer takes place over a given area orsurface. The choice of heating system, from gas/oil or heatpump, to electric resistance, will also affect the payback ofadditional wall insulation due to variation in energy fuelprices. For regions identified as “cold,” careful attentionshould be made in selecting energy fuel type; inparticular, a heat pump may not be a practical option.

A homeowner exploring designs and construction methodsshould examine the value of using structural insulatedpanels. The incorporation of high levels of insulationdirectly from the factory on building wall and ceilingcomponents makes them outstanding barriers to heat andmoisture. These integrated systems, if appropriately used,can save substantial amounts of energy when comparedwith traditional stick-built systems using 2×4 or 2×6lumber. Also, building energy-efficient features (as well aselectrical, plumbing, and other elements) directly into thebuilding envelope at the factory can result in labor costsavings over the more traditional methods of construction.

Floor InsulationWarm air expands and rises above surrounding cooler air.This process of heat transfer is called convection. Warmair, which is lighter, rises and, as it cools, falls, creating aconvection current of air. The two other processes of heattransfer are conduction (kinetic energy transferred fromparticle to particle, such as in a water- or electricallyheated floor) and radiation (radiant energy emitted in theform of waves or particles such as in a fireplace or hotglowing heating element). Floor insulation limits all threemodes of heat loss. A warmer floor reduces the temperaturedifference that drives convection. Floor insulation alsodirectly impedes conduction and radiation to the colderair below the floor.

Batt Insulation The advantage of floor insulation lies in adding extraR-value without a significant increase in cost. It is cheaper to

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Figure 13.2. Potential Effects of Radiant Barriers [3]

put more insulation under the floor than to add foamsheathing or change the type of wall construction toaccommodate greater insulation levels.

Like walls, floor cavities should be completely filled withinsulation-without gaps, missing insulation, or cavityvoids. Floor insulation must contact the subfloor andboth joists. In many cases, it is worth the extra cost tobuy enough insulation to fill the entire cavity.

The amount of floor insulation required by some codescan be less than the space available. For example, an R-19fiberglass batt is 6¼ inches thick. A floor framed with2×8s is about 7½ inches deep, while a 2×10 floor is9½ inches deep. A builder following a code’s minimuminsulation level will leave extra space that will allow forgreater heat loss. To avoid this situation, the batt must bepushed up into the cavity. With the proper support, thiscan be done. Springy metal rods are commonly used tohold insulation up in the top of the floor cavity. Anotherviable option is the use of plastic straps. Figure 13.3shows batt insulation improperly applied to the floorabove a crawl space or a basement.

The thickness of typical fiberglass batts can assist thedesigner and the builder in creating a floor system thatworks for the occupants. Table 13.3 shows a list of R-values,along with the associated batt thickness. Individualbrands can vary by as much as 1 inch.

Cavity Fill According to Oikos, a commercial Web site devoted toserving professionals whose work promotes sustainable

design and construction, “Buying a thicker batt may be abetter option than trying to lift a thinner batt into theproper position. Material costs will climb slightly but laborshould be the same. Attaching the insulation support to thebottom of the floor joist will be easier. It could also lead to ahigher quality job because there is less chance forcompression or gaps” (Figure 13.4) [4].

In some areas, it’s common to hang plastic mesh overfloor joists. Installers drop the insulation onto the meshbefore the subfloor isinstalled. However,hanging the meshcreates sagging bellies.Insulation compressesnear the framing andsags in the middle. Meshshould be attached to thebottom of the floorframing [4].

Each stage of increasedfloor insulation, fromR-19 to R-30 or R-30 toR-38, can save energy overthe life of the house. This energy translates into energysavings that are multiples of the initial installation costs.Floor insulation will generate the greatest savings incolder climates; in moderate climates, the targetinsulation level should depend on economics.

Blow-In InsulationA blown-in insulation system allows the builder orinsulator to fill the entire cavity completely, even aroundpipes, wires and other appurtenances. Using well-trainedinstallers will pay dividends in quality workmanship.

DoorsToday there is an endless variety of doors, ranging frommetal doors with or without insulation to hollow core tosolid 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 athermal break between the interior and exterior metalsurfaces; this keeps heat from being transferred from oneside to the other.

Standard DoorsBecause doors take up a small percentage of a wall,insulating them is not as high a priority as is insulatingwalls and ceilings. That said, heat loss follows the path ofleast resistance; therefore, doors should be selected that

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Figure 13.3. Common Floor Insulation Flaws [4.] Two common flaws in floorinsulation 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 thehouse. Doors usually have lower R-values than thesurrounding wall.

Storm doors can add R-1 to R-2 to the existing door’s R-value. They are a valuable addition to doors that arefrequently used and those that are exposed to cold winds,snow, and other weather. Screens allow natural breezes tocirculate air from outside, rather than totally relying onair-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 conventionalwood doors.

Sliding Glass DoorsAlthough sliding glass doors have aesthetic appeal, theyhave very low R-values and hence are minimally energyefficient. To improve the energy efficiency of existingsliding glass doors, the homeowner should ensure thatthey seal tightly and are properly weather-stripped.Additionally, heavy insulated drapes with weights, whichimpede the airflow, can cut down on heat loss throughsliding glass doors.

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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 overthe 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 bestapled every 12 to 18 inches.

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

Door InstallationDoors must be installed as recommended by themanufacturer. Care must be taken to be sure that doorsare installed in a manner that does not trap moisture orallow unintended introduction of air. Numerous types ofsealing materials are available that range from foam toplastic, to metal flanging and magnetic strips.

Hot Water SystemsThe hot water tank can be insulated to make it moreefficient, unless the heat loss is used within the spacewhere it is located. Special insulation is available for thistype of appliance, and insulating it will reduce the energyrequired to deliver the hot water needed by the occupantsof the dwelling. Of course, any pipe that is subject toextreme temperatures also should be insulated to decreaseheat loss.

WindowsWindows by nature are transparent. They allow occupantsof a dwelling to see outside and bring in sunlight andheat from the sun. They make space more pleasant andoften provide lighting for tasks undertaken in the space.Especially in the winter, these desirable characteristicsoffset the heat loss. Heat gain in the summer throughwindows can be undesirable.

Rather than give them up, it is important to use windowsprudently and to keep energy considerations in mind intheir design and their insulating characteristics (air, glass,plastic, or gas filler). Good design takes advantage of daylighting. Weather-stripping and sealing leaks aroundwindows can enhance comfort and energy savings. EnergyStar windows are highly recommended. Housekeepingmeasures can improve the efficiency of retaining heat.Heat loss follows the path of least resistance: caulking,weather-stripped framing, and films can help. Thesemeasures are relatively labor intensive, low to very low incost, and can be quite satisfying to the homeowner ifaccomplished correctly. On the other hand, it is not easyfinding the perfect materials or even replacement parts forold windows.

When working with older windows, remember that thereis the risk for leaded paint and the dispersion of toxic leaddust into the work area. Please refer to the lead section ofChapter 5, Indoor Air Pollutants and Toxic Materials.

Caulking and Weather-Stripping According to the U.S. Department of Energy, caulkingand weather-stripping have substantial housekeeping benefits in preventing energy loss or unwanted heat gain.

CaulkingCaulks are airtight compounds (usually latex or silicone)that fill cracks and holes. Before applying new caulk, oldcaulk or paint residue remaining around a window shouldbe removed using a putty knife, stiff brush, or specialsolvent. After old caulk is removed, new caulk can thenbe applied to all joints in the window frame and the jointbetween the frame and the wall. The best time to applycaulk is during dry weather when the outdoortemperature is above 45°F (7.2°C). Low humidity isimportant during application to prevent cracks fromswelling with moisture. Warm temperatures are alsonecessary so the caulk will set properly and adhere to thesurface [5].

Weather-strippingWeather-stripped frames are narrow pieces of metal, vinyl,rubber, felt, or foam that seal the contact area betweenthe fixed and movable sections of a window joint. Theyshould be applied between the sash and the frame, butshould not interfere with the operation of the window [6].

Replacing Window Frames The heat-loss characteristics and the air tightness of a windowvary with the type and quality of the window frame. Thetypes 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 mostairtight and inexpensive choice, but are not suited toplaces that require ventilation. The air infiltrationproperties of casement windows (which open sidewayswith hand cranks), awning windows (which are similar tocasement windows but have hinges at the top), andhopper windows (inverted awning windows with hingesat the bottom) are moderate. Double-hung windows,which have top and bottom sashes (the part of thewindow that can slide), tend to be leaky. The advantageof the single-hung window over the double-hung is that ittends to restrict air leakage because there is only onemoving part. Horizontal sliding windows, though suitablefor small, narrow spaces, provide minimal ventilation andare the least airtight.

In buildings with large older windows, there are oftenweight cavity areas that hide counter balances that makeit easy to raise and lower heavy windows. These areasshould be insulated to reduce energy loss.

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Tinted WindowsAnother way to conserve energy is the installation oftinted windows. Window tinting can be installed that willboth conserve energy and also prevent damaging ultravioletlight from entering the room and potentially fading woodsurfaces, fabrics, and carpeting. Low-emissivity coatings,called low-e coatings, are also available. These coatings aredesigned for specific geographic regions.

Reducing Heat Loss and Condensation The energy efficiency of windows is measured in terms oftheir U-values (measure of the conductance of heat) ortheir R-values. Besides a few highly energy-efficientexceptions, window R-values range from 0.9 to 3.0.When comparing different windows, it is advisable tofocus on the following guidance for R- and U-values:

• R- and U-values are based on standards set by theAmerican Society of Heating, Refrigerating, andAir-Conditioning Engineers [7].

• R- and U-values are calculated for the entirewindow, which includes the frame.

• R- and U-values represent the same style and sizeof windows.

The R-value of a window in an actual house is affected bythe type of glazing material, the number of layers of glass,the amount of space between layers and the nature of thegas filling them, the heat-conducting properties of the frameand spacer materials, and the airtightness associated withmanufacturing.

For windows, rating and approval by the National FenestrationRating Council or equivalent rating and approval isstrongly recommended [8].

Please refer to the window section of Chapter 6, HousingStructure.

GlazingGlazing refers to cutting and fitting windowpanes intoframes. Glass has been traditionally the material of choicefor windowpanes, but that is changing. Several newmaterials are available that can increase the energyefficiency of windows. These include the following:

• Low-emissivity (low-e) glass uses a surface coatingto minimize transmission of heat through thewindow by reflecting 40% to 70% of incidentheat while letting full light pass through the pane.

• Heat-absorbing glass is specially tinted to absorbapproximately 45% of the incoming solar energy;some of this energy passes through the pane.

• Reflective glass has a reflective film that reduces heatgain by reflecting most of the incident solar radiation.

• Plastic glazing materials such as acrylic,polycarbonate, polyester, polyvinyl fluoride, andpolyethylene are stronger, lighter, cheaper, andeasier to cut than glass. However, they are lessdurable and tend to be affected by the weathermore than glass is.

• Storm windows can improve the energy efficiencyof single-pane windows. The simplest example ofstorm windows would be plastic film, available inprepackaged kits, taped to the inside of thewindow frame. Because this can affect visibilityand be easily damaged, a better choice would beto attach rigid or semirigid plastic sheets such asplexiglass, acrylic, polycarbonate, or fiber-reinforced polyester directly to the window frameor mounting it in channels around the frame onthe outside of the building. Care should be takenin installation to avoid ripples or blemishes thatwill affect visibility.

LayeringThe insulating capacity of single-pane windows is minimal,around R-1. Multiple layers of glass can be used to increasethe energy efficiency of windows. Double- or triple-panewindows have air-filled or gas-filled spaces, coupled withmultiple panes that resist heat flow. The space betweenthe panes is critical because the air spaces that are toowide (more than 5/8 inch) or too narrow (less than ½ inch)allow excessive heat transfer. Modern windows use inertgases, such as argon and krypton, to fill the spacesbetween panes because these gases are much moreresistant to heat flow than air is. These gas-filled windowsare more expensive than regular double-pane windows.

• Frame and spacer materials may be aluminum,wood, vinyl, fiberglass, or a combination of thesematerials, such as vinyl- or aluminum-clad wood.

• Aluminum frames are strong and are ideal forcustomized window design, but they conduct heatand are prone to condensation. The deteriorationof these frames can be avoided by anodizing orcoating. Their thermal resistance can be boosted

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using continuous strips of plastic between theinterior and exterior of the frame.

• Wood frames are superior to aluminum frames inhaving higher R-values, tolerance to temperatureextremes, and resistance to condensation. On theother hand, wood frames require considerablemaintenance in the form of painting or staining.Improper maintenance can lead to rot or warping.

• Vinyl window frames made from polyvinylchloride are available in a wide range of styles andshapes, can be easily customized, have moderateR-values, and can be competitively priced. Largewindows made of vinyl frames are reinforcedusing aluminum or steel bars. Vinyl windowsshould be selected only after consideration of theconcerns surrounding the use of vinyl materialsand their off-gassing characteristics.

• Fiberglass frames have the highest R-values andare not given to warping, shrinking, swelling,rotting, or corroding. Fiberglass is not weather-resistant, so it should also be painted. Somefiberglass frames are hollow; others are filled withfiberglass insulation.

• Spacers separating multiple windowpanes in awindow use aluminum to separate glass inmultipane windows, but it conducts heat. Inaddition, in cold weather, the thermal resistancearound the edge of such a window is lower thanthat in the center, allowing heat to escape andcondensation to occur along the edges.

• Polyvinyl chloride foam separators placed alongthe edges of the frame reduce heat loss andcondensation. Window manufacturers use foamseparators, nylon spacers, and insulation materialssuch as polystyrene and rock wool insulationbetween the glass panes inside windows.

Other OptionsShades, shutters, and drapes used on windows inside thehouse reduce heat loss in the winter and heat gain in thesummer. The heat gain during summer can also be minimizedby the use of awnings, exterior shutters, or screens. Thesecost-effective window treatments should be considered beforedeciding on window replacement. By considering orientation,day lighting, storage of or reflection of energy fromsunshine, and materials used within the house and on thebuilding envelope, heat loss and gain can be decreased.

Solar EnergySolar energy is a form of renewable energy available tohomeowners for heating, cooling, and lighting. The moreenergy-efficient new structures are designed to store solarenergy. Remodeled structures may be retrofitted to increaseenergy efficiency by improving insulation characteristics,improving airflow and airtightness of the structure, andenhancing the ability to use solar energy. Solar energysystems are active and passive. Whereas active solar systems usesome type of mechanical power to collect, store, anddistribute the sun’s energy, passive systems use thematerials and design elements in the structure itself.

Active Solar SystemsActive solar systems use devices to collect, convert, anddeliver solar energy. Solar collectors on roofs or othersouth-facing surfaces can be used to heat water and airand generate electricity. Active solar systems can beinstalled in new or existing buildings and periodicallyneed to be inspected and maintained. Active solar energyequipment consists of collectors, a storage tank, piping orductwork, fans, motors, and other hardware. Flat panelcollectors (Figure 13.5) can be placed on the roof or onwalls. Typically, the collector will be a sandwich of one ortwo sheets of glass or plastic and another air space above ametal absorber plate, which is painted black to enhanceheat absorption. After collection, when the sun’s energy isconverted to heat, a transfer is made to a liquid storagetank. The heated liquid travels through coils in the hotwater tank, and the heat is transferred to the water andperhaps the heating system. Most hot water systems use aliquid collector system because it is more efficient and lesscostly than an air-type system.

In the southwest United States, solar roof ponds havebecome popular for solar cooling. Evaporative coolingsystems depend on water vaporization to lower thetemperature of the air. These have been shown to be moreeffective in dry climates than in areas with extremely highrelative humidity.

In certain climates, like those in the Hawaiian Islands,using solar energy is cost-effective for providing hot water.

Figure 13.5. Solar Panels13-9Healthy Housing Reference Manual

Some builders even include it as a standard feature intheir homes. The total cost to the homeowner of solarenergy systems consists of the capital, operational, andmaintenance costs. The real cost of capital may belowered by the availability of tax credits offered at thefederal (to lower federal income taxes) and state levels.

Homeowners and builders can benefit from tax creditsbecause they lower the total upfront investment cost ofinstalling active solar systems. This is the major portion ofthe total cost of using solar energy, because operation andmaintenance costs are small in comparison to initialsystem costs.

Passive Solar SystemsBuildings designed to use passive solar energy havefeatures incorporated into their design that absorb andslowly release the sun’s heat. In cold climates, the designallows the light and heat of the sun to be stored in thestructure, while insulating against the cold. In warmclimates, the best effect is achieved by admitting lightwhile rejecting heat. A building using passive solarsystems may have the following features in the floor plan:

• Large south-facing windows

• Small windows in other directions, particularly onthe north side of the structure

• Designs that allow daylight and solar heat topermeate the main living areas

• Special glass to block ultraviolet radiation

• Building materials that absorb and slowlyreradiate the solar heat

• Structural features such as overhangs, baffles, andsummer shading to eliminate summeroverheating.

Passive design can be a direct-gain system when the sunshines directly into the building, thereby heating it andstoring this heat in the building materials (concrete, stonefloor slabs, and masonry partitions). Alternatively, it maybe an indirect gain system where the thermal mass islocated between the sun and the living space. Isolatedgain is yet another type of system that is separated fromthe main living area (such as a sunroom or a solargreenhouse), with convective loops for space conditioninginto the living space.

Energy Star is a program supported and promoted by theU.S. Environmental Protection Agency (EPA) that helpsindividuals protect the environment through superiorenergy efficiency. For the individual in his or her home,energy-efficient choices can save families about one thirdon their energy bill, with similar savings of greenhousegas emissions, without sacrificing features, style, orcomfort. When replacing household products, look forones that have earned the Energy Star; these productsmeet strict energy-efficiency guidelines set by EPA andthe U.S. Department of Energy. When looking for a newhome, look for one that has earned the Energy Starapproval. If you are planning to make largerimprovements to your home, EPA offers tools andresources to help you plan and undertake projects toreduce 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 andavoid greenhouse gas emissions equivalent to those from20 million cars-all while saving $10 billion.

Conducting an Energy AuditEnergy audits can help identify areas where energyinvestments can be made, thereby reducing energy used inlighting, heating, cooling, or meeting other demands ofhousing occupants. An inspection can evaluate theworthiness or compliance with codes of energy-savingmeasures, including accepted or written standards. Forexample, if a new addition requires the equivalent of R-19insulation in the ceilings, this can be validated in theinspection process. Whereas an audit is generallyinformational, an inspection should validate thatmaterials and workmanship have yielded a structure thatprotects the occupants from the elements, such as rain,snow, wind, cold, and heat. Potentially hazardoussituations within a structure should be evaluated in aninspection. The overall goal of a housing inspection in thecase of energy efficiency is to identify potential hazardousconditions and help to create conditions under which thehealth and welfare of the occupants can be enhanced,rather than put at risk.

The housing inspector should be aware that there isvariation (sometimes quite significant differences) inheating degree days or cooling loads and in relativehumidity conditions within given regions. Local andregional topography, as well as site conditions, can affecttemperatures and moisture.

Numerous Web sites listed in this chapter’s AdditionalSources of Information section discuss the procedures forconducting energy audits. Local and regional utilities

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often offer audit services and assist with selecting cost-effective conservation measures for given areas of theUnited States.

References1. Lawrence Berkeley National Laboratory. Energy

star insulation project: R-value guidelines.Berkeley, CA: Lawrence Berkeley NationalLaboratory; 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, EnergyResources and Technology Division. Ceilinginsulation. Honolulu, HI: State of Hawaii,Department of Business, Economic Development,and Tourism; no date. Available fromURL:http://www.hawaii.gov/dbedt/ert/rf_insul.html.

4. Oikos. Filling a floor with batt insulation. EnergySource Builder 1995 [Apr]; 38. Available fromURL: http://oikos.com/esb/38/floorinsulation.html.

5. US Department of Energy. Energy savers: factsheets. Washington, DC: US Department ofEnergy; no date. Available from URL:http://www.eere.energy.gov/consumerinfo/factsheets.html.

6. US Department of Energy. Advances in glazingmaterials for windows. Washington, DC: USDepartment of Energy; 1994.

7. American Society of Heating, Refrigerating andAir-Conditioning Engineers (ASHRAE).Standards; no date. Atlanta: American Society ofHeating, Refrigerating and Air-ConditioningEngineers. Available from URL:http://www.ashrae.org.

8. National Fenestration Rating Council. Search forenergy 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 isEnergy Star? Washington, DC: US EnvironmentalProtection Agency; no date. Available from URL:http://www.energystar.gov/index.cfm?c=about.ab_index.

Additional Sources of InformationAlliance to Save Energy. Save energy at home. Availablefrom URL: http://www.ase.org/section/_audience/educators/edsavhome/.

Christian J, Kosnay J. Home Calculating whole wall R-values 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 environmentalproblems. 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 Developmentand Tourism. Ceiling insulation. Available from URL:http://www.state.hi.us/dbedt/ert/rf_insul.html.

National Association of State Energy Officials. Availablefrom URL: http://www.naseo.org.

Nexus Energyguide. Available from URL:http://www.energyguide.com/default.asp.

Oak Ridge National Laboratory Buildings TechnologyCenter. Available from URL:http://www.ornl.gov/ORNL/BTC.

Oak Ridge National Laboratory. Whole-wall thermalcalculator performance. Available from URL:http://www.ornl.gov/roofs+walls/whole_wall/wall-a30.html.

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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 theEnergy Tax Incentives Act of 2003. Available from URL:http://energy.senate.gov/news/rep_release.cfm?id=203374.

Trandt J. Americans want energy efficiency. Availablefrom URL: http://healthandenergy.com/energy_efficiency.htm.

US Department of Energy, Energy Efficiency andRenewable Energy. Building envelope. Available fromURL: http://www.eere.energy.gov/EE/buildings_envelope.html.

US Department of Energy, Energy InformationAdministration. Available from URL: http://eia.doe.gov/.

US Environmental Protection Agency. Available fromURL: 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 aconfusing issue. EBN 1998 7(4). Available from URL:http://www.buildinggreen.com/features/tm/thermal.cfm.

World Energy Efficiency Association. Available fromURL: http://www.weea.org/.

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