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WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 4-1
Chapter 4: Insulation
IntheWashington State Energy Code (WSEC),insulationlevelsexpressedinR-valuesaredeterminedbythecom-pliancepathasexplainedinChapter1, Compliance.Forbelow-gradewallsandslab-on-gradeinsulationdetailsseeChapter2,Foundations.Forabove-gradewallconstructionandinsulationdetails,seeChapter3, Framing.Generalinsulationrequirements,regardlessofcompliancepath,areoutlinedinthischapter.
Installingtheproperamountofinsulationisimportant,butcorrectinstallationtechniquesareofequalimportancetoachievespecifiedR-values.
[502.1.4.6] CompletelyFillAllExteriorWallCavitiesandInsulatetotheFullRequiredR-Value.Exteriorwallcavitiesarecon-sideredtobeanywallseparatingaheatedspacefromanunheatedspace.Areasthataresometimesoverlookedare:
• Behindshowerorbathtubenclosures (seeFigure4-1).
• Whereinteriorandexteriorwallsmeet.• Corners.• Stairwellstounheatedbasements.• Skylightchasesthroughattics.• HVACductworkinexteriorwalls,floorsand
ceilingscannotdisplacerequiredinsulation.
Exception: A framed cavity can be empty or partially filled, provided both of the following conditions are met: • The wall assembly calculations are performed along with a completed performance calculation for the whole building. • Insulation installed in partially filled cavities is not included in the performance calculation.
Chapter 4-2 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program
Figure 4-1
Tub Enclosure on Exterior Wall
WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 4-3
Figure 4-2
Electrical Box Insulation Details
[502.1.4.1] Don’tCompresstheInsulation.Compressionofinsula-tionwillcauseittobelessefficient.Forexample,ifyoucompressanR-19battinhalf,youreducetheR-valuebyalmost50percent.Commonareasofcompressionare:
• Behindoutletandswitchboxes.• Behindplumbingpipesandwiring.
Compressionproblemscanbeavoidedinthesesituationsbycuttingandfittinginsulationaroundoutletandswitchboxes(seeFigure4-2).Slicingabouthalfwaythroughabattwillallowittofitaroundawireorpipe.
Chapter 4-4 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program
Figure 4-3
[502.1.4.6] InsetStaplingFacedBattsisnotAllowed.Iffacedbattsareused(kraftpaperorfoilfacingmaterial)andiftheyhaveastaplingtab,theymustbestapleddirectlytothefaceofthestud.Staplingtothesideofthestudcompressestheinsula-tionandcreatesaconvectiveairchannelthatreducestheeffectivenessoftheinsulation(seeFigure4-3).
Face Stapling
WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 4-5
[502.1.4.5] AtticBaffles. Bafflesarenecessarytomaintainairspacebetweentheinsulationandtheroofsheathingwhensoffitorbirdblockventingisused(seeFigure4-4).Thispro-motescross-ventilationoftheattic,helpingtoremoveunwantedmoisture.Itminimizespotentialrotproblems,andicedamminginwinter.
Bafflesaremadeofweatherresistantmaterial,typicallywax-impregnatedcardboard.Bafflesmustextend:
• 6inches(vertically)abovenon-compressedbatttypeinsulation.
• 12inches(vertically)abovefulldepthblown-ininsulation.
Figure 4-4
Attic Baffles in Standard Frame Ceiling
Chapter 4-6 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program
[502.1.4.4] AtticAccess. Abaffleordamaroundanatticaccesshatchisalsorequiredwhenloose-fillorblown-ininsulationisinstalled(seeFigure4-5).Requirementsforaccesshatchesanddoorsare:
• Woodframe,orequivalent,baffleinstalledaroundtheopening.Cardboardisnotacceptable.
• ThehatchmustbeinsulatedtothesameR-valueasthesurroundingceilingwithbattorrigidinsulation.
• Thehatchmustbeweatherstrippedtostopairleakagebetweentheatticandtheinterior.
Figure 4-5
Attic Hatch
WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 4-7
FloorInsulationSupports. Floorinsulationmustbeinstalledinapermanentmannerandinsubstantialcontactwiththesurfacebeinginsulated(seeFigures4-6,4-7and4-8).Insulationcanbeheldinplaceusing:
• Polyethylenetwine.• Lath.• Otherapprovedmaterial.
Figure 4-6
Floor Insulation Supports
[502.1.4.1,502.1.4.7]
Chapter 4-8 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program
Supportsarerequiredtobeamaximumof24inchesapart.Iftheinsulationthicknessismoreorlessthanthedepthofthejoist,hangersareavailabletoholdtheinsulationtothefloorsurfacewithoutcompressingit.Metalrodsorothersupportsthatcompresstheinsulationarenotacceptable.
Ifinsulationdepthislessthanthedepthofthejoist,insettwiningorsupportsarerequired(seeFigure4-7).
Postandbeamfloorsrequireadifferentinsulationattach-mentapproach.Theinsulationissupportedbylathandsupportsareattachedtothepostsandfoundationwall(seeFigure4-8).
Figure 4-7
Underfloor Insulation
WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 4-9
Figure 4-8
Post and Beam Insulation Supports
[502.1.4.7,Exception] Ineithertypeoffloor,wheninsulationabutsafoun-
dationvent,abafflemustbeinstalledtodeflecttheincomingairbelowtheinsulationlevel.Thesebafflesaretypicallymadeofplywoodorwaximpregnatedcard-boardinstalledata30°angle(referbacktoFigure2-2).
Substantialcontactwiththesurfacebeinginsulatedisnotrequiredinafloor/ceilingassemblycontainingduct-workwhenfulldepthinsulationisinstalledbetweentheductandexteriorsurfaces.Thisexceptiononlyapplies
[502.1.4.7,Exception]
Chapter 4-10 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program
toenclosedfloor/ceilingassemblieswithanairbarrierexterioroftheinsulation,separatingtheassemblyfromunconditionedspace(seeFigure4-9).
Loose-FillInsulation. Loose-fillorblown-ininsulationiscommonlyinstalledinceilings(seeFigure4-10).Thefollowingrequirementsapplywhenusingloose-fillinsulation:
• Theceilingpitchmustbe3-in-12orless.• Code-approvedbafflesmustbeinstalled.• Theremustbeaminimumof30inchesofclear
distancefromthebottomchordofthetrusstothesheathingattheridge.
• TheinsulationmaterialmustcomplywiththeIBCforflamespreadandsmokedensityrequirements.
• R-valuemarkersmustbeinstalledevery300sq.ft.
Figure 4-9
Substantial Contact Exception
[502.1.4.5,502.1.4.1]
WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 4-11
[502.1.4.4] Ifareasoftheatticneedtobeaccessibleforequipmentmaintenance,acatwalkshouldbeconstructedandsup-portedabovetheloose-fillinsulation(seeFigure4-11).
Figure 4-10
Loose-fill Insulation Requirements
Figure 4-11
Cat Walk
Chapter 4-12 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program
SkylightWalls. Skylightwallsareinsulatedtothesamelevelastheotherwallsinthehouse.Duetoconstructionmethodsandcloseproximityofrooftrusses,thesewallsaremoredifficulttoinsulatethanastandardexteriorwall.
Acommonskylightwallinsulationtechniqueistotackinsulationbattsontheoutsideoftheframedwallsandsecureitinplacewithtwine. Remember, a vapor retarder is required. Thevaporretarderfacestheinside,orwarmside,asexplainedinChapter5,page5-1.
[502.1.4.5] Whentwoormorelayersofrigidboardinsulationareusedinaroofassembly,theverticaljointsbetweeneachlayerarestaggered.