www.ag.ndsu.nodak.edu • 1

AE-1368 (Revised)

March 2010

North Dakota State UniversityFargo, North Dakota 58105

Conditioned air in your home can belost in three ways. Heat moves froma warm to a cold place by conduction,convection or radiation. Conductedheat moves through a material.Convected heat is carried by a movingfluid, such as circulating air or water.Radiated heat passes through a space(air) and warms objects it strikes. Forexample, the sun warms the Earth,but not the space between them.A building loses heat by conductionthrough construction materials, byexhausting warm air that is replacedby cold outdoor air and by radiationto or from surfaces. Simple measurescan insulate walls economically andeffectively to resist heat flow.

Radiant heat loss affects the comfortlevel. Animals or people lose heatby radiant heat transfer when theyare surrounded by a surface that islower in temperature than their bodytemperature. Radiant heat loss causesyou to feel cool when sitting in frontof a window on a cold winter day,even though the room air temperaturemay be 75 degrees Fahrenheit (°F).

Although all building materialshave some insulation value, the term“insulation” usually refers to materialswith a relatively high resistance toheat flow that are designed specificallyfor that purpose. R-value is a termthat describes the ability of a materialto resist heat flow. The higher theR-value, the better the insulation.

Where to Focus FirstThe major areas of heat loss in thetypical home are the walls, ceiling,foundation, windows, doors andair leaks. Air leaks are areas in thehome where air can pass directlyfrom one room to another or to orfrom the outside without resistance.A gap around a door is an example,but homes have many moreplaces that allow heat to escape.Depending on the construction ofthe home, homeowners generallyshould concentrate on the airleaks or infiltrations first, andthen insulate areas that are belowrecommended levels.

Determining what areas in thehome are in greatest need of energyefficiency upgrades will take a littleinvestigation. First determine theclimate zone in which you live fromFigure 1 (see page 2). Using the recom-mendations from Table 1 (see page 2),check to see how much insulationyou should have in each area ofyour home and determine whereadditional insulation would bemost beneficial. For example:If you have double-glazed windowsand 16 inches of insulation in the attic,but no insulation on your foundation,concentrating on the foundationwould make more sense. For adetailed examination to determineif your house is inefficient, referto appendix A.

Reduce Heating CostsCarl Pedersen

Energy Educator

Kenneth Hellevang, Ph.D., P.E.Professor, Extension Engineer

In North Dakota,

50 percent of energy

used in homes is for

heating and air conditioning.

Properly insulating your home

not only saves money,

but also makes the home

more comfortable.

Insulating to

2 • A-1368 Insulating to Reduce Heating Costs

ComparingInsulation CostsR-value is the ability of a materialto prevent heat transfer. Thickermaterials do not always have higherR-values. The R-value of a 6-inchrigid piece of polystyrene has anR-value of 30, while a 6-inchfiberglass blanket will have anR-value of about 21. Does thatmake the polystyrene a better buy?Not necessarily. The fiberglass maybe less expensive or easier to install,or have better properties for theparticular application. To determinea cost per R-value, simply divide thecost of the insulation by the R-value.Then figure in the cost of installationand other associated costs.

Figure 1.Climate zone map ofNorth Dakota. Based onheating degree days (HDD).Zones identified as A and Bare used in Table 1.(International Code Council, 2006)International Code Council, 2006)International Code Council, 2006)International Code Council, 2006)International Code Council, 2006)

Table 1. Insulation values for North Dakota. Insulation value of windows is given in both a U-factor and R-valuefor comparison purposes. Window ratings generally are given as U-factor, which is the inverse of R-value.

Where basement and crawl space insulation requirements have two different values: The first R-value applies tocontinuous insulation, the second to framing cavity insulation. Crawl space wall R-value shall apply only to unventilatedcrawl spaces; R-5 shall be added to the required slab edge R-values for heated slabs; and floors over outside air mustmeet ceiling requirements. (International Code Council, 2006)

Foundation Types

Floor overWindow U Window R Wood-framed unheated Basement Slab Crawl

factor factor Ceiling wall space wall perimeter space wall

Zone A 0.35 2.86 R-49 R-19 R-30 R-10/13 R-10, 4ft R-10/13Zone B 0.35 2.86 R-49 R-21 R-30 R-10/13 R-10, 4ft R-10/13

Doing it Yourselfor Choosing anInsulation ContractorAfter you determine if you need moreinsulation, the next decision to makeis if you are going to hire a contractorto perform the installation or do ityourself. The overriding concern isthat while some insulating jobs aredone easily, others require specialskills or equipment. Insulating aneasily accessed attic with blankets offiberglass or your exterior foundationmay be relatively simple. Insulatingthe wall cavity in living spaces maybe quite involved.

If you decide to have the work donecommercially, you need to know twothings: 1) Where to look for thecontractor, and 2) How to choose aqualified and reputable contractor forthe job. To find a contractor, check inthe Yellow Pages under InsulationContractors. Then consult the localchapter of the National Associationof Home Builders, your local energyprovider or a trusted real estate agent.Put together a list of three to fourcontractors for comparison. Start byasking each contractor for references.Reputable installers gladly willprovide references.

Other places to research an installerare the Chamber of Commerce,Better Business Bureau and stateregulatory agency. Once referencesare checked, ask the contractors fora detailed estimate. Never assumethat specific tasks are going to beperformed unless those tasks arestated in writing. Be sure to compareestimates equally; one estimate mayrequire the homeowner to performcleanup while another may not.Choose the contractor who bestfits your needs and budget.

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Types of InsulationThe material the insulation is madeof refers to the type of insulation.Cellulose or wood fiber insulationis made from used newsprint, otherpaper feedstock or wood. Chemicalsare added to provide fire resistance.Fiberglass insulation is made fromglass heated and drawn out to formlong fibers. While it can cause skinirritation, fiberglass is noncorrosive,has no objectionable odor and doesnot burn. Rock wool or slag wool issimilar to fiberglass in the manufac-turing process and properties.

Polystyrene insulation comes ineither a molded or extruded form.Molded polystyrene, or “bead board,”is less expensive, but has a lowerR-value per inch. It also absorbs moremoisture than extruded polystyrene.Extruded polystyrene is fine-texturedand moisture-resistant. Both moldedand extruded polystyrene degradethrough time with exposure tosunlight, so they need a protectivecovering. They are also flammableand will release toxic substanceswhile burning, so they need to becovered with gypsum board orother fire protection.

Polyurethane insulation is a cellularplastic that has a high R-value perinch. It typically is applied as a foamor rigid board. A similar type topolyurethane is polyisocyanurate.Both are flammable and releasetoxic substances while burning.Icynene is a newer sprayed-on,expanding foam insulation.It remains flexible and does notabsorb water as easily as otherinsulation types.

Table 2. Typical R-value for common building materials.Most values are from the 2005 American Society of Heating,Refrigerating and Air-Conditioning Engineers (ASHRAE) Foundationand will vary depending on construction.

R-value

Material Per Inch For thickness listed

Batt and blanketFiberglass or wool 3.00 to 3.80

Polyurethane 6.00

Polyisocyanurate 7.04

Icynene 3.6

Cellulose 3.13 to 3.70

Hay or straw, 20 inch ~1.5 30+

Extruded polystyrene boards 5.00

Solid concrete .08

Plywood (d-inch) 1.25 .47Plywood (½-inch) 1.25 .62

Softwoods, fir and pine 1.25

Hardwoods, maple and oak .91

Windows, insulating glass,¼-inch air space

Double pane 1.69Triple pane 2.56

Doors, exterior (includes air space)Wood, solid core, 1¾-inch 3Metal, urethane core, 1¾-inch 10

Forms of InsulationThe form of the insulation refers tothe shape it takes as it is applied.Fiberglass and rock wool insulationgenerally comes in batts or blankets.A batt is a precut section of insulationgenerally 4 or 8 feet long, while ablanket is a much longer roll – up to100 feet or more. Batts and blanketsmay be faced or unfaced. Faced battshave a paper or foil backing thatshould be installed toward the heatedliving space. The backing, a vaporretarder, limits moisture from enteringthe insulation and reducing itseffectiveness. The vapor retardersoften are referred to mistakenly asvapor barriers. While they do reducethe amount of vapor that passesthrough the material, they are not acomplete barrier. Unfaced batts may

be used with an external vaporretarder or to increase insulationlevels where the retarder alreadyexists. Thicknesses range from1 inch to 9 inches and widths of16 or 24 inches to match stud spacing.

Loose-fill insulation comes in bagsand can be blown in with a machineor poured. Common loose-fillmaterials include cellulose, rock wool,vermiculite, polystyrene beads andfiberglass. While most commonlyused in ceilings, loose-fill insulationapplications include filling coresin concrete blocks and insulatingstud wall cavities.

Rigid-board insulation may bemade from cellulose fiber, fiberglass,polystyrene or polyurethanes.A common size for rigid-board

4 • A-1368 Insulating to Reduce Heating Costs

insulation is 4 feet by 8 feet, withthicknesses ranging from ¼ inch upto 4 inches. Rigid boards may beused on the inside or outside ofwalls and, in some cases, on exteriorbelow-grade walls. Depending onyour location, many building codesrequire polystyrene and polyurethaneboards must be covered with a15-minute, fire-rated thermalcovering if used on the inside of ahouse. This type of covering willprovide a thermal barrier that willkeep the temperature rise of theinsulation below 250°F for atleast 15 minutes in case of a fire.

Some covering materials with the15-minute rating are at least ½-inchexterior-grade plywood treatedwith fire retardant, ½-inch-thickportland cement plaster andfired-rated sheetrock or gypsumboard. They commonly are usedin remodeling construction,especially for basement walls.

Sprayed-in-place insulation is appliedduring construction to a stud wallcavity. Spray-on insulation containsan adhesive that sticks to the surfacebeing insulated. The most commonmaterials are cellulose, polyurethane,fiberglass and Icynene. Polyurethaneand Icynene insulation have theability to expand when applied,which makes them capable ofgetting into cracks and voids otherinsulations would miss, whichsignificantly reduces air infiltration.

Both are gaining popularity inresidential applications, butpolyurethane has been usedextensively in commercial oragricultural buildings. According toMinnesota building code, rim joistareas in new construction must becovered with spray-on insulation.

Applying InsulationAtticWhatever type of insulation youinstall, make sure you have a vaporbarrier between the living space andthe insulation. If you add batt orblanket insulation over pre-existinginsulation, be sure to buy the insula-tion without paper or foil backing.

Begin in the attic by attempting tolocate air infiltration areas. Sealingleaks should be accomplished beforeinsulation is installed or added.Look for gaps around plumbing orheating penetrations. Also take noteof interior walls that extend into theattic. If the tops of these walls arenot sealed, warm air can enter thewalls and escape from the livingspace. The walls act like funnelsfor heat loss.

Recessed lighting also presentsa problem for insulating. The lightsextend into the attic, creating possibleareas for air infiltration, as well asreduced insulation surrounding thelights. Modern recessed lights aresealed to prevent air infiltration.Insulated boxes can be constructedto surround recessed lights. Do notforget to insulate the access area intothe attic.

Run weather-stripping around accessdoors and cover the door withinsulation. Commercial tents can bepurchased that fit over attic accessdoors or one can be made easily withrigid insulation. Once the air leaks aresealed, begin the work of insulating.

Batt and loose-fill insulation are themost common materials used toinsulate attics, depending on theconstruction. Some attics have afloor over the top of the ceiling joists,but most are open with exposed joists.If flooring is in place, loose-fillinsulation can be blown under the

floorboards. However, removingthe flooring can make insulatingeasier and allow the homeownerto use all types of insulation.While putting loose-fill insulationover the floor might be the easiestinstallation method, it preventsstoring anything in the attic, so mosthomeowners would object to this.An option is to place rigid-boardinsulation on top of the attic floor andcover it with plywood. If attic storagecannot be given up, concentrate thestorage next to the attic door tominimize the insulation loses.

If the attic does not have anyinsulation, buy insulation batts orblankets wide enough to fit betweenthe ceiling joists. If you already haveinsulation up to the top of the joists,you can place additional material atright angles to the joists to minimizeheat loss due to seams.

If adding batts or blankets, decidewhat thickness should be used. Thisdepends on a number of things: thecost of the project, the free space inthe attic and the current R-value. TheDepartment of Energy recommendshouses in North Dakota have an atticinsulated with an R-value of 49. Thisis the least amount of insulation youshould strive to have in place.

The cost of more insulation mayoutweigh the benefits. Using therecommended R-values per inchfor fiberglass insulation in Table 2, anR- value of 49 would require around16 inches of insulation. To determinethe amount or square feet to buy,multiply the length of the attic by itswidth. If the attic consists of severaloddly shaped areas, figure eacharea separately and add the totals.

To prevent moisture problems in theattic, you must provide 1 square footof air vent for each 300 square feet ofattic floor. Include half at the eavesand half at or near the peak.

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If working in an attic without afloor, use temporary flooring toavoid stepping between joists andpossibly falling through the ceiling.A few planks or a piece of ¾-inchplywood works well.

Be sure to leave clearance betweenthe insulation and the roof near theedge of the attic floor (Figure 2). Thisclearance is necessary so air from thesoffit vents can enter the attic andenable moist attic air to leave.This will prevent moisture problemsin the attic. If you use loose-fillinsulation, you will need to preventthe material from falling down intothe soffit and covering the vents.You can do this by using a bafflemade of cardboard, wood or rigidinsulation. Baffles also can bepurchased at a building supply store.

In many homes, getting adequateinsulation depths at the attic edge andstill maintaining a minimum 2-inchclearance below the roof is difficult.In this case, you can cut rigidinsulation into pieces to fit snuglybetween the rafters. Lay these pieceson top of the insulation at the edgeof the attic. The rigid insulation hasa higher R-value per inch than othermaterials, and a piece of it placedhere will insulate well and still giveenough clearance for ventilation.

Adding insulation to a cathedralceiling generally requires a contractor.The contractor will add insulationover the roof, then reroof or addinsulation to the inside ceiling andrefinish it (Figure 3).

WallsInsulating walls is best accomplishedduring renovations. If siding is to bereplaced, rigid-board insulation canbe applied to increase the R-value.Interior walls can be insulated afterremoval of wall coverings. Insulatethe wall cavities by using the samemethods used to insulate an attic.

If adding insulation without majorrenovations, loose-fill and foaminsulation are the common forms.For both, a hole must be drilled intoeach wall cavity to add insulation.While the hole may be drilled fromthe inside, it most often is drilledfrom the outside. The holes can behidden by removing a piece of siding,drilling the holes and then replacingthe siding, which leaves no visibleevidence of the work.

Figure 2.A well-insulated attic also must be awell-ventilated attic. If you insulatewith loose fill, make a baffle out ofcardboard, foam insulation or woodand insert it as shown to preventinsulation material from fallingdown into the soffit vents.(NDSU)

Applying loose-fill insulation requiresdrilling a hole at the top or bottom ofthe cavity and blowing insulation intothe space. Problems exist with loose-fill insulation not completely fillingthe space due to obstructions, such aswiring and plumbing, or the house

Figure 3.Insulating cathedral ceilings. Both the exterior and the interior ofa cathedral ceiling can be insulated. Exterior insulation is appliedto the top of the roof and a new roof is installed over the insulation.To insulate the interior, furring strips are installed on the ceiling andthe insulation is placed between the strips.(NDSU)

Insulating outside a cathedral ceiling Insulating inside a cathedral ceiling

6 • A-1368 Insulating to Reduce Heating Costs

settling through time. Foamed-in-place insulation requires a series ofholes drilled into the wall, withspacing and sequence depending onthe construction. While foam insula-tion costs are higher than for loose-fillinsulation, foam insulation will notsettle. Due to the difficulty insulatingbehind existing walls, this is generallybest left to the professionals.

Knee WallsKnee walls are found in houses withfinished attics. The knee wall is theshort wall that reaches from thesloped ceiling to the floor, Figure 4.Not only are air leaks common inthese areas, but they are frequentlynot insulated properly. The knee wallsgenerally have exposed studs behindthem and can be insulated with battsor blankets. Make sure the vaporretarder backing insulation is nextto the living space. If the studs arecovered on the backside, you caninsulate the knee wall by drilling ahole in the covering near the top ofthe wall and filling the cavity withblown insulation.

The sloped area above the ceilingis a more difficult to insulate.Block the rafter cavity at the bottomand fill it with a loose-fill insulationpoured from the attic over the ceiling.You can insulate the floor behind theknee wall and the attic above it thesame way you would a regular attic.

Crawl SpacesBatts or blankets are about the onlypractical way to insulate a floor overa crawl space or unheated basement.While rigid insulation will work, itgenerally will cost more per R-valuein this application. The insulation fitsbetween the floor joists and is held inplace with wire netting across thebottom of the joists. Use a 6-milpolyethylene vapor barrier on top

of any bare soil to prevent moisturefrom getting into the crawl space.If the crawl space contains air ductsor water pipes, insulating the walland allowing the space to achievea stable temperature to preventpipes from freezing would be better.Frequently, these crawl spaces arebeing treated as mini-basementsto minimize moisture problems.

BasementEither the outside or inside of aheated basement can be insulated.If finishing the basement, insulatingthe interior wall surfaces is theeasiest. If the basement already isfinished, or if plans are not to finishit, insulate the exterior wall surface.A basement insulated on the outsideof the walls has more heat storagethan those insulated on the inside.The concrete stays warmer and willrelease heat to the house if the homeheating system temporarily fails.Insulating the outside of the wallsalso keeps the footing warm, limitingthe potential for soil movement dueto freezing.

Figure 4. Insulating attic knee walls.

Seal all air leaks first.

Then insulate the back side of the knee walland attic floor behind the knee wall (A) or insulate

the sloped area above the ceiling behind the knee wall (B).

The first step to insulate the insideof the foundation wall is attachingvertical furring strips or 2-inch by4-inch framing, Figure 5. Put batt,blanket or rigid insulation betweenthe strips. Batt or blanket insulationwith vapor retarders can be installedby stapling the edges of the retarderto the front of the furring strips.Be sure a vapor retarder exists. Battand blanket insulation is becomingless common in basement insulationdue to moisture problems. Moisturecan enter the insulation from eitherside, reducing its R-value and creatingthe potential for mold growth.Rigid insulation is becoming theinsulation of choice for basements.

Polystyrene rigid insulation isthe most common basement wallinsulation due to its higher R-valueand better moisture resistance.Simply glue rigid insulation tothe wall and finish the wall with a15-minute fire-rated thermal covering.Rigid insulation is used to insulatethe outside of a basement wall bothabove and below the ground level.

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Remove the soil from the outsidefoundation wall to a depth of 4 feetand glue the rigid insulation tothe foundation with constructionadhesive. Make sure to cover anyexposed above-ground insulationto prevent degradation by the sunand other elements, Figure 6.

An often overlooked area for airinfiltration and poor insulation is therim joist. This is the area where thewall framing meets the foundation.Cut rigid insulation to fit these areasand caulk the seams to ensure theleast amount of air infiltrationpossible. (see Figure 7, page 8.)Cover the insulation with a 15-minutefire barrier. Fiberglass insulationalso can be used in the rim joists,but a vapor retarder must beinstalled to reduce moisture problems.Make sure to check local and statebuilding codes to determine whatis required in your area.

Insulation should extend at least four feet beneath ground level. Figure 6.

Applying insulation to an exterior foundation wall.(NDSU)

Figure 5.Insulating abasement wallfrom the inside.(NDSU)

8 • A-1368 Insulating to Reduce Heating Costs

Applying InsulationHere are some general insulation installation tips:

• Use a utility knife or large shears to cut batts or blankets to fit snuglybetween joist and sills.

• Use insulated boxes around recessed light fixtures.Check local building codes for other restrictions and regulations.

• When using batts and blankets, place long runs first.Use the remaining pieces to fill in the smaller areas.

• Adhesives, vapor retarders and some insulation are flammable.Be sure to keep open flames away.

• Repair any roof leaks or damage before insulating.

• Make sure the attic has adequate ventilation to prevent the buildupof moisture. Often moisture freezes during the winter, then dripsinto the living space at the first thaw.

• Attach a piece of rigid or batt insulation to attic access doors andmake sure the door is weather-stripped.

• Wear a dust mask, long-sleeved shirt and gloves when handlinginsulation. Fibers and chemicals can be transferred to clothing,so wash the clothing separately.

Figure 7.Insulating the rim joist

and sealing air leakswith rigid insulation.

Insulation needs to becovered with a 15-minute

fire barrier.Photo courtesy of the

Family Handyman Magazine.

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Appendix A

Calculate Home Energy Heating EfficiencyThe heating energy index shows how efficiently energy is used in a home.

The index allows a comparison as improvements are made or between houses.It takes into account the average winter conditions, types of heating fuels and house construction.

Consisting of two steps, the first involves calculating the overall index for the heated spaces.

Knowing this value, you can make a decision to determine where thelargest heat transfer occurs by calculating heating coefficients.

Heating Energy Index Calculations

STEP 1. Determine heating energy use.The first step calculates the amount of energy the house requires in an average heating season. Enter the fuel type andquantity of fuel used from October to April for each energy type.

Table 1. Energy usage.

Type of Energy _______________ Type of Energy _______________

Month Month

October _______________ October _______________

November _______________ November _______________

December _______________ December _______________

January _______________ January _______________

February _______________ February _______________

March _______________ March _______________

April _______________ April _______________

Total _______________ Total _______________

STEP 2. Convert fuel use to BTUs.To determine the amount of energy required to heat the home, enter the amounts from Table 1 above into theappropriate blank below, then multiply it by the number given. This converts energy use to British thermal units (BTU).

Electricity ____________ kilowatt-hours (kwh) X 3,413 = ________________ BTU

Natural gas __________ hundreds of cubic feet (CCF) X 100,000 = ________________ BTU

Natural gas ___________ dekatherms X 1,000,000 = _______________ BTU

Fuel oil _____________ gallons X 140,000 = _______________ BTU

LP gas ______________ gallons X 95,000 = _______________ BTU

10 • A-1368 Insulating to Reduce Heating Costs

Climatography of the U.S. No. 81 – Supplement 3Maps of Annual 1961-1990 Normal Temperature,Precipitation and Degree Days(James Owenby, Richard Heim Jr., Michael Burgin, Devoyd Ezell)

City Heating Degree Days

Bismarck 8,802Bottineau 10,288Bowman 8,682Cavalier 10,195Devils Lake 9,424Dickinson 8,558Ellendale 8,441Fargo 9,092Grand Forks 9,489Jamestown 8,999Minot 8,990Williston 9,044

Climatography of the U.S. No. 81. 1971-2000

Heating Degree Days (HDD) ___________

STEP 3. Find the degree days.Using the map at right, get the best estimate forthe heating degree days (HDD) for your area.An HDD is calculated by subtracting the dailyaverage temperature from 65 °F. So if the outsideair temperature is 45 °F on a particular day, theHDD would be 20 (65 °F minus 45 °F). The HDDfor the entire year is the sum of the daily HDDs.

STEP 4. Find the area (square feet) of heated space.To determine the area of heated space, multiply the length of the house by the width.If the house has unheated space, subtract this from the total. Do not include unheated basements.

Square Feet (FT2) ____________

STEP 5. Calculate the Heating Energy index.Use this number to compare the house with other houses. Once upgrades are completed, also use this number to see howefficiently the house uses energy.

A. Begin by dividing the total BTU by the degree days. This will give the BTU used for each degree day.

BTU———————— = ____________ BTU/HDD

DEGREE DAYS

B. Next, divide the result of BTU/HDD in step A by the area of your house (STEP 4).This will give you the heating energy index.

BTU/HDD———————— = _______________________________ heating energy index

FT2

C. Now compare this heating energy index with the values from the thermometer on page 11 to see how efficientlyyour home uses energy.

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Example CalculationThis example is included to enable you to understand how to calculate your home‘s heating energy index.The example home uses natural gas as a fuel for a central heating system, clothes dryer and water heater.The basement contains an electrically heated heated room. The electricity used by the electrical appliances

and lights are also included in this analysis, since the heat they produce helps to heat the house.

STEP 1.Because the example home uses two types of fuel for heating. Step 1A would be done like this:

Type of Energy ________________ Type of Energy ________________

Units ________________ Units ________________

MONTH MONTH

October ________________ October ________________

November ________________ November ________________

December ________________ December ________________

January ________________ January ________________

February ________________ February ________________

March ________________ March ________________

April ________________ April ________________

TOTAL ________________ TOTAL ________________

Natural Gas Electricity

CCF KWH

MONT

154 303

289 376

439 354

257 412

278 461

185 363

104 325

1706 2594

In the example used, the house has an index of 12.5. It could use some improvements to lower the heating costs.

STEP 2.In converting the example home’s heating use to BTUs (British Thermal Units), we get:

Electricity ____________ KWH X 3,413 = ________________

Natural Gas ____________ CCF X 100,000 = ________________

Total = ________________

STEP 3.If the example home is in Minot, its degree days will be approximately:

Heating Degree Days (D.D.) _____________

STEP 4.Find the square footage of the heated parts of the home. In our example, we mustremember to add the square feet of the electrically heated room in the basement.

Square Feet (FT2) _____________

STEP 5.Find the Energy Index for the example home. The calculations would be done like this:

A. 179,453,322 B. 19,939—————— = 19,939 BTU/D.D. ————— = 12.5 Heating Energy Index9,000 D.D. 1,600 FT2

2594

1706

8853322

170600000

179453322

9000

1600

12 • A-1368 Insulating to Reduce Heating Costs2M-7-08; 2M-3-10

Visit us on the web at:www.ndsu.edu/energy

Additional ResourcesASHRAE 2005.

ASHRAE Handbook – Fundamentals.American Society of Heating Refrigeration andAir-Conditioning Engineers Inc. Atlanta, Ga.

ICC 2006.International Energy Conservation Code.

International Code Council Inc. Falls Church, Va.

USDOE 2005.Your Home: Knee Wall Insulation and Air Sealing.

U.S. Department of Energy, Energy Efficiency and Renewable Energy.Available at www.eere.energy.gov.

Accessed April 10, 2008.

This publication is an update, revision and compilation of various Extension publications.

DisclaimerThe report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor

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