Asnewbuildingandinsulationmaterialshaveenteredthe
market,confusionoverthenatureandmeaningof"R"-valuehasraised
questionsamongbuildingprofessionalsandconsumersalike.Whatexactlyis
"R"-value?Isitaneffectiveandobjectivemeasureofthethermal
performanceofaninsulationproductorconstructionsystem?Andhowshould
themarketplaceuseittocomparethebenefitsofoneinsulationmaterial
overanother?
Defining"R"-value
Duringthe1970s,asdemandforqualitybuilding
insulationsoared,anoilcrisissentheatingandcoolingcostsskyward.
Withmanynewproductsonthemarket–andwithsomanyconflictingclaims
pertainingtotheinsulatingabilitiesofthoseproducts–theFederalTrade
Commission,withtheparticipationandsupportoftheinsulationindustry,
createdanobjectivemethodforreportingtheperformanceofresidential
insulationmaterials.Thismethodiscalledthe"R"-valueRule.
TheRuleprovidesrequirementsforproductlabeling
("R"-value)andadvertising,andmandatesspecificASTMmethodsforthermal
testing.The"R"-valueRulehasbeenhelpfulincomparingdifferentbrands
ofthesametypeofinsulatingmaterial.However,asmoresophisticated
materialsandhighertechnologyconstructionsystemsareintroducedintothe
buildingindustry,wefindthatthe"R"-valueofamaterialdoesnottell
thewholestory.
"R"-valueisbasedonamathematicaltermknownas
"R"-factor.Theterm"R"-valuewasdevelopedtorepresenttheabilityofan
insulationmaterialtorestrictheatflow.Itisdeterminedbyplacingtest
specimensbetweentwoplatesinalaboratoryapparatusand
heat-flowthroughtheinsulation.Thetestspecimenusuallyconsistsofa
squarefootofmaterialexactlyoneinchthickwhosesurfaceshavea
temperaturedifferentialof1degreeFahrenheit.Thethermalconductivity
(k)ofamaterialisexpressedastherateofheatflowinBTUsperhour.
Thermalresistance(R)ofamaterialisitsresistanceto
heatflow,and"R"-valueisexpressedasthereciprocalofthematerial’s
thermalconductivity.Simplyput,thegreaterthe"R"-valuethebetterthe
insulation.
WhyStandard"R"-valueTestingisInsufficient
FullbackcontouredEPSfoamproductscannotbetested
underASTMC177or518,whichareprescribedfortestingonlyflat
(consistentthickness)sheets.Fullbackmustbetestedusingthe"Guarded
HotBoxTest"outlinedinASTMC236.Thissametestmethodisusedtotest
windows,etc.,wherevariousthicknessesandcomponentsareinvolved.
Thesetestscanonlybeconductedbyagovernment
approved,thirdparty,testinglaboratory.ProgressiveusesATI,locatedin
York,Pennsylvania.
GuardedHotBoxTest
Bywayofexplanation,when"R"-valuesare
required,ATI,withProgressive’sinput,buildsaspecificbasewallto
depictanewconstructionorresidingwallandmountsitinan8'x8'test
fixture.Thefixtureisclosedandsealed.Aheatsourceislocatedonthe
inputsideofthewallandacoolingchamberislocatedontheoutputside
ofthewalltocontroltemperature.
Priortosealingthefixture,thelab
personnelaffixalargenumberofthermocouplestodesignatedlocationson
bothsidesofthetestwall.Thesethermocouplesareusedtomeasurethe
surfacetemperatureintheirimmediatearea.Thisandotherbitsof
informationaretransmittedintoacomputer.Itreadsthedata,storesit
andlaterprocessesitthroughaprogramwhichmeasuresthewall’s
resistancetoheatflow.
Theheatingandcoolingsystemsarethen
turnedon.Thecoldsideisbroughtto0°Fandthewarmsideisbroughtto
70°F.Thesetemperaturesareallowedtostabilizeforaperiodof
twenty-four(24)hours.Thecomputerprogramisthenstartedandthe
measurementofenergyinputismeasuredagainstthetimetheheattakesto
passthroughthewallandbemeasuredontheoutputside.
Thistestproducesan"R"-valueforthebase
wall.Forexplanationpurposes,let’ssaythatthewallproducesan
"R"-valueof5.0.Thefixtureisopenedontheinputside,thethermocouples
areremovedandourFullbackproductisinstalledwiththerespectivevinyl
siding,exactlyasitwouldbeonthehouse.Thermocouplesareonceagain
affixedtotheinputsideandthefixtureisclosedandsealed.
Thetemperaturestabilizationprocess
referredtoaboveisagaincompleted.Thetestisthenrunonthe
combinationoftheoldwallandthenewproduct.Forexample,let’ssaythat
the"R"-valueproducedfromthistestisanR-9.Inordertodeterminethe
system"R"-valueyousimplysubtractthebasewall5.0fromthecomposite
wallof9.0andyouhaveasystem"R"-valueof4.0.
Thesystem"R"-valuetakesinto
considerationthedifferencesinthicknessofthefoamandgivesyouan
averagewhichisfullyacceptedbytheinsulationindustryandthe
government.
TheProblemwithSomeOtherFoamInsulatingMaterials
Thereareotherfactorsthataffectthe
performanceofinsulationproductsaftertheyareinstalledinabuilding,
includingthermaldrift.
Dependingontheinsulationmaterialused,
the"R"-valuecanslowlybereducedovertimeasthematerialages.Some
foamplasticinsulationmaterialsuseblowingagentsthathaveahigh
resistancetoheatflow,causingtheinsulationtohaveanabnormallyhigh
"R"-valueatthetimeofmanufacture.Itisnowknownthattheseblowing
agentsdiffusethecellularstructureofthefoamuntilalevelof
equilibriumisreachedmanyyearsafteritismanufactured.Asthehigh
"R"-valuegasesdiffuseoutofthecellularstructure,theabilityofthe
insulationtopreventthermalflowisreduced,losingupto30percentof
itsoriginalinsulatingability.
Fullbackdoesnotusethesetypesofblowing
agents;therefore,itsinsulationperformanceremainsstableoveritsentire
life.
WallSystem"R"-value
Whenthe"R"-valueRulewasinstituted,most
homesandbuildingswereconstructedandinsulatedusingdimensionallumber,
two-by-fours,andfiberglassinsulation.Toahome’sinsulation,
generally,abuilderwouldhaveselectedafiberglassinsulationproduct
thathadahigher"R"-value,buttodaywehavelearnedthatitisn’t
necessarilythe"R"-valueoftheinsulationthatmakesthewallmore
efficient.Itisacombinationofinsulationmaterials,constructiondetails
andinstallationcarethatprovideultimatethermalperformance.
Todayweunderstandthattoinsulatethe
spacebetweenthestudswithfiberglassisnotthesameasinsulatingan
entireexteriorwall.Wemustconsiderthewallasasystem.Thelumber
createsthermalbridgingandairinfiltrationwithinthewall.Nowweknow
thatitisimportanttoinsulatetheentire"WallSystem"andnotjustthe
areabetweentheframingmembers.
EnergyEfficiency
Fullback®ThermalSupportSystems
providethelong-termefficiencynowdemandedbytheconstructionindustry.
Heatingandcoolingahomeaccountfor50to70percentoftheenergycosts
experiencedintheaveragehome.Inmonetaryterms,theU.S.consumesalmost
$40billioninairconditioningaloneaccordingtotheEPA.Thestable
thermalperformanceofEPSinsulationresultsinheatingandcoolingsavings
thataddupoverthelifeofthestructure.Inaddition,areductionof
energyusealsohelpstoconservenonrenewablefuelsupplies.
Thedecreaseduseoffuelandenergy
translatesintoreducedairpollution.TheEPAalsoreportsthathousehold
electricityaccountsfor35percentofallU.S.emissionsofcarbon
dioxides,75percentofsulfurdioxideand38percentofnitrogenoxides.By
utilizingmoreenergyefficientmaterialsandproductsinourhomes,wecan
reducetheamountofairpollution.
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Updated6/13/201010:38:10AM
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