WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-1

Design Conditions

TheWashington State Energy Code(WSEC)setsthefollow-ingconditionsforheatingsystemdesignandequipmentsizing:

[302.2.1] • Indoor Design Temperature:70°Fheating-78°F cooling.

EXCEPTION: Other design temperatures may be used provided they result in lower energy consumption.

• Outdoor Design Temperature:BasedonlocalweatherdatatakenfromTable3-1ofthe2009WSEC.IfyoucannotfindaparticularlocationlistedinTable3-1,useasitenearyourlocationwithsimilarweatherconditions.

• Recommended Air Infiltration Rate for Equipment Sizing:0.6airchanges/hour(ACH).0.6ACHisaliberalairinfiltrationestimateforhomesmeetingcoderequiredinfiltrationratesof.00030SLA.ThisinfiltrationrateisfromtheAirConditioningContractorsofAmerica(ACCA)Manual JTable5Adefaultinfiltrationratesduringtheheatingseason.

.6ACHistheassignedinfiltrationratefora1,501-2,000sq.ft.homewithaverageairleakage.Infiltrationratesforsmallerorlargerhousesofsimilarconstructionwillvaryslightly.

Design Heat Load (DHL) Calculation[503.2.1] Heatingandcoolingdesignloadsforthepurposeofsizing

theheatingand/orcoolingequipmentmustbecalculatedinaccordancewithacceptedengineeringpractice,includ-inginfiltrationandventilation.

Chapter 7: Heating and Cooling Systems

[302.1]

Chapter 7-2 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program

[503.2.2] System Sizing Limit. TheCoderequiresthatsystemsbesizedasrequiredin International Residential Code(IRC)SectionM1401.3.IRCM1401.3statesthatsystemsbesizedusingACCAManualSandManualJorotherapprovedcal-culationmethods.ManyjurisdictionsallowtheuseoftheheatingsystemsizingcalculatorsthatareincorporatedintotheWSU Extension Energy Program Prescriptive Compliance and Component Performance worksheets.YoushouldcheckwiththegoverningjurisdictiontoseeiftheyaccepttheWSUExtensionEnergyProgramforms.

TheWSECallowssomeexceptionstosystemsizinglimitations.

• Packagedequipmentthatprovidesbothheatingandcooling,suchasaheatpump,needonlyshowcompliancefortheheatingorcoolingsizinglimit.Theunitshouldbesizedforthelargerofthetwoloads.

• Ifinstallingagasoroilfurnaceandthesystemsizeislessthan40,000Btu/hr,itisexemptfromsizinglimits.

• TheWSECallowstheinstallationofstandbyequipmentifcontrolsareinstalledthatonlyallowthestandbyequipmenttooperatewhentheprimarysystemisnot.

• TheCodealsoallowstheinstallationofelectricresistanceheaterslessthan2kWwithoutsizinglimitations.

WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-3

Figure 7-1

Electric Resistance Heating Systems

(503.4) HVAC Equipment Performance Requirements

Electric Resistance Heating Systems

System efficiency. Norequirement.Electricresistanceheatingisconsidered100percentfuelefficient.

Combustion Heating Systems

System efficiency. A minimum78percentAFUEisrequired.

• Oil,gas,orpropanespaceheatersrequireanintermittentignitiondeviceandmustmeet1987NAECAefficiencyrequirements.

• Chapter9ofthe2009WSECgives1.0creditforsystemsinstalledwitha92percentAFUEorgreater.

Chapter 7-4 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program

Figure 7-2

Combustion Heating Systems

Heat Pumps

System efficiency.

Air Source:

• Forsplitandsinglepackagesystems,aminimumof7.7HeatingSeasonalPerformanceFactor(HSPF)forheatingand13.0SeasonalEnergyEfficiencyRatio(SEER)isrequiredforcoolingforsystemsunder65,000Btu/h(seeWSECTable14-1B).

• Chapter9ofthe2009WSECgives1.0creditforsystemsinstalledwithanHSPFof8.5orgreater.

WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-5

Figure 7-3

Split Package Heat Pump OptionsDucted

Outdoor unit with compressor and heat exchange coil

Air handler with blower and heat exchange coil

Ductless

Chapter 7-6 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program

Ground Source

• MinimumCoefficientofPerformance(COP)=3.1Chapter9ofthe2009WSECgives2.0creditsforsystemsinstalledwithaCOPof3.3orgreater.

Figure 7-4

Ground Source Closed Loop SystemFrom EERE.ENERGY.GOV

[503.8] Controls. Applicable to all system types

Aprimaryspaceconditioningsystemmusthaveapro-grammablethermostatasitscontrol.Ataminimum,theprogrammablethermostatmusthavethecapabilitytoprogramtemperaturesettingsforfiveweekdaysandtwoweekenddays.Inaddition,thethermostatmustbeabletobeprogrammedfortwosetbackperiodsperday.

WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-7

TheCodealsostatesthateachadditionalspacecondition-ingsystemwithinadwellingunitshallbeprovidedwithatleastoneadjustablethermostatfortheregulationoftemperature.Anexampleofthismaybeahousewithelec-tricresistancewallheatersforitsheatingsystem.Themainlivingareacouldbecontrolledbyaprogrammablethermo-statwhilethebedroomsandbathroomswouldhavetheirheaterscontrolledbyindividualandadjustablethermostats.

TheWSECallowstwoexceptionsforspacecondition-ingcontrolrequirements.Anoccupantsensormaybeusedinsteadofaprogrammablethermostat.Theoccupantsensormustshutoffthesystemwhennooccupantsaredetectedforaperiodofupto30minutes.

Atimercontrolmaybeinstalledifthetimerlimitstheoperationofthesystemtotwohours.

TheWSECrequiresthateachthermostatshallbecapableofbeingsetbyadjustmentorselectionofsensorsasfollows:

• Whenusedtocontrolheatingonly:55°Fto75°F

• Whenusedtocontrolcoolingonly:70°Fto85°F.

• Whenusedtocontrolbothheatingandcooling,thethermostatshallbecapableofbeingsetfrom55°Fto85°Fandshallhaveanadjustabledeadbandofnotlessthan10°Fbetweenhotandcold.

• Iftheheatpumphasanelectricresistancebackupheatingsystem,acontrolthatlocksoutthestripheatneedstobeinstalled.Thecontrolmustpreventthebackupsystemfromoperatingwhentheheatingloadcanbemetbytheheatpumpalone.

• Havethecapabilitytolockoutsupplementaryheatingbasedonoutdoortemperature.TheCoderequiresthatthecontrolhasamaximumsettingof

Chapter 7-8 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program

40°Fandissetto32°Fatfinalinspection.Iftheheatpumpwillnotmeettheheatingloadatthe320,thelockoutcanbesethigherbutnotabove400

.

– Lockoutcapacitymaybemetbyexternalorinternalcomponents.Programmablethermostatswithlockoutcapabilityoraftermarketdevicesthatmeetthetemperaturerequirementsnotedaboveareexamplesofexternallyappliedlockoutmechanisms.Someheatpumpsmayhavelockoutcapabilitybuiltintothesystem.

Duct Systems

Insulation Requirements

[503.9] Ducts,plenums,andenclosuresoutsideconditionedspacesuchascrawlspaces,atticsorgaragesmustbeinsulatedtoR-8.Ductsandplenumsonroofsand/ortheexteriorofbuildingsmusthaveanapprovedweatherproofbarrier.TheseductsneedtobeinsulatedtoR-8inClimateZone1andR-10inClimateZone2.DuctsandplenumsinslabsorinthegroundshallbeinsulatedtoR-5withmaterialapprovedforbelowgradeapplicationforbothclimatezones.Extrudedpolystyreneistypicallyusedforthisrequirement.

Exceptions:

Ducts do not have to be insulated when:

1. The heat gain or loss of the ducts, without insulation, will not increase the energy requirements of the building.

2. Ducts are within HVAC equipment.3. Exhaust air ducts. Some exhaust air ducts are required to be

insulated by the Washington State Amendments to the IRC.4. Supply or return air ducts installed in basements or cellars in

one and two-family dwellings.

WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-9

5. The insulation required on supply air ducts may be reduced to R-4 when the ducts are located in buffer spaces not intended for human occupancy such as insulated crawl spaces and enclosed attic spaces. To use this exception, the buffer space must be air sealed and insulated to the full value of the conditioned spaces.

Duct Fasteners

DuctsmustbefastenedinaccordancewiththeInterna-tional Mechanical Code(IMC).Forsmallsheetmetalducts,aminimumofthreescrewsperconnectionequallydistrib-utedaroundtheduct,orequivalentisrequired.Forflexduct,andductboard,youmustfollowinstructionsdevel-opedbytheSMACNA,notedintheIMC.Moreinforma-tioncanbefoundat:www.smacna.org/

[503.10] Buildingcavitiesmaynotbeusedasducts.Youmayrunaductthroughabuildingcavitybutinstallationoftheseductsinexteriorwalls,floorsorceilingsshallnotdisplacerequiredenvelopeinsulation.

Leakage Testing

DuctsshallbeleaktestedinaccordancewithRS-33(availableatwww.energy.wsu.edu/code),usingoneofthemaximumductleakageratesspecifiedbelow:

• Postconstructiontest.Thistestistypicallydoneatornearcompletionofconstruction.

– Leakageratetooutdoorsshallbelessthanorequalto6percentoftheconditionedfloorareatestedat25pascalspressure.Thistestmeasuresductleaksthatareoutsideoftheconditionedspace.Toperformthistestyouneedaducttesterandablowerdoor.

Or

Chapter 7-10 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program

– Totalleakagerateshallbelessthanorequalto8percentoftheconditionedfloorareatestedat25pascalspressure.

• Rough-intest.ThistestisdoneimmediatelyaftertheHVACsystemisinstalled.Thisisthepreferredtimetotestsotheductsarestillexposedandanyleakageareasareaccessible.

– Totalleakagerateshallbelessthanorequalto6percentoftheconditionedfloorareatestedat25pascalspressure.

Or

– Totalleakageshallbelessthanorequalto4percentoftheconditionedfloorareatestedat25pascalspressureiftheairhandlerisnotpresent.Toaccomplishthistestyouneedtotestthesupplyductsandthereturnductsandaddtheleakageratestogether.

EXCEPTIONS: 1. Duct testing is not required if the air handler and all ducts are

located within the conditioned space.

2. Duct testing is not required if the furnace is a nondirect vent type combustion appliance installed in an unconditioned space. This is an atmospherically vented furnace installed outside the conditioned space, usually in a garage. This exception allows a maximum of six feet of connected ductwork in the uncon-ditioned space. All additional supply and return ducts need to be inside the conditioned space.

WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-11

Figure 7-5

Duct Insulation and Sealing

Duct Sealing

Allduct,airhandlerandfilterboxseamsandjointsshallbesealed.

Primarysealantsapprovedforductsincludewelds,gaskets,masticormasticswithembeddedfabricsystems.Tapesmaybeusedifspecificinstallationproceduresprovidedbythemanufacturerarefollowed.

Chapter 7-12 WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program

Figure 7-6

Sealing Ducts

(Not Allowed)

WSEC Builder’s Field Guide, 8th Edition, 2009 • Washington State University Extension Energy Program Chapter 7-13

Tapesmustbeinstalledinaccordancewiththemanufacturer’sinstructions,orinthecaseofUL181sealants,inaccor-dancewiththeproductlisting.Iftheproductdoesnothaveinstructionsspecifictothematerialorapplicationitisbeingappliedto,itdoesnotmeettheintentoftheCode.Forexample,iftapeisusedtosealsheetmetal,instruc-tionspublishedbythemanufacturermustincludenotesonapplicationtosheetmetal.Ifthesheetmetalneedstobecleaned,themanufacturer’sinstructionsmustprovidespecificinstructionsoncleaning.Theseinstructionsmustbefollowedbytheinstaller.

Foradditionalinformationonductsealing,seetheBuilder’s Field Guide’s Supplement A,“ImprovingForcedAirHeatingSystems.”