Download - SWA Report on WWSV Heating Systems
-
8/14/2019 SWA Report on WWSV Heating Systems
1/23
BuildingAmericaSystemsEvaluation
Simple,Non
Distributed
Heating
Systems
inColdClimateHomes
PREPAREDFOR:
NATIONALENERGYTECHNOLOGYLABORATORY
3610COLLINSFERRYROAD
MORGANTOWN,WV
265070880
&
MIDWESTRESEARCHINSTITUTE,
NATIONALRENEWABLEENERGYLABORATORYDIVISION,
1617COLEBOULEVARD,
GOLDEN,CO
804013393
PREPAREDBYSTEVENWINTERASSOCIATES,INC.
FORTHE
CONSORTIUMFORADVANCEDRESIDENTIALBUILDINGS(CARB)
STEVENWINTERASSOCIATES,INC.
50WASHINGTONSTREET
NORWALK,CT06854
TEL:(203)8570200/FAX:(203)8520741
CONTACT: ROBBALDRICH
-
8/14/2019 SWA Report on WWSV Heating Systems
2/23
Table of Contents1.
EXECUTIVE SUMMARY .................................................................................................... 3
1.1. Overview ........................................................................................................................ 3
1.2. Key Results ................................................................................................................... 3
1.1. Gate Status .................................................................................................................... 3
2. PROJECT OVERVIEW RDI WISDOM WAY SOLAR VILLAGE ..................................... 4
2.1. Plans .............................................................................................................................. 4
2.2.
Basement ...................................................................................................................... 4
2.3. Above-Grade Walls ....................................................................................................... 4
2.4. Attic ................................................................................................................................ 5
2.5. Windows ........................................................................................................................ 5
2.6. Heating Systems ........................................................................................................... 6
2.7. Ventilation Systems ..................................................................................................... 6
2.8.
Water Heating ............................................................................................................... 7
2.9. Solar Electric Systems ................................................................................................. 7
3. SHORT-TERM TESTING .................................................................................................... 7
3.1. Research Questions ..................................................................................................... 7
3.2. Blower Door, Airflow, and Power Measurements ...................................................... 8
3.3. Tracer Gas and Temperature Distribution Testing Procedure ................................. 9
3.4. Air Distribution Results ............................................................................................... 9
3.5. Thermal Comfort Analysis and Results ................................................................... 113.5.1. Thermal Design Considerations ............................................................................................................. 113.5.2. Thermal Comfort Test Results ............................................................................................................... 12
3.6. Recommendations to Residents ............................................................................... 17
4. LONG-TERM MONITORING AND EVALUATION ........................................................... 17
5.
GATE CRITERIA .............................................................................................................. 17
5.1. Must Meet Criteria ................................................................................................... 175.1.1. Source Energy Savings and Whole Building Benefits ............................................................................ 175.1.2. Performance-Based Code Approval ....................................................................................................... 18
5.2. Should Meet Criteria ............................................................................................... 185.2.1. Prescriptive Code Approval .................................................................................................................... 185 2 2 Cost Ad antage 18
-
8/14/2019 SWA Report on WWSV Heating Systems
3/23
Building America System Evaluation
NON-DISTRIBUTED HEATING SYSTEMS IN 50% COLD-CLIMATE HOMES
1. Executive Summary
1.1. Overview
Asenvelopeperformancedramaticallyincreasesincoldclimatehomes,designheatingloads
becomeverysmall. BuildingAmericateamshavestruggledtofindsystemssmallenoughto
meettheseloadsefficiently,comfortably,andcosteffectively. AtWisdomWaySolarVillagein
Greenfield,MA,RuralDevelopmentInc.(RDI)isbuildinghomeswithexceptionalthermal
envelopes. Toheateachhome,asingle,gasfired,sealedcombustionroomheaterislocatedinthecentrallivingspaceofeachhome. Thereisnoheatprovideddirectlytobedrooms,thougha
simpleventilationsystemprovidessomethermalequalization. CARBhasperformedshortterm
testinginconjunctionwithNRELinFebruary2009,andlongtermmonitoringisunderwayfor
thewinterof20092010.
1.2. Key Results
ShorttermtestresultsfromFebruary2009indicatedthattemperaturedistributionthroughout
thetested
home
would
be
acceptable
under
nearly
all
conditions.
At
outdoor
temperatures
above1015F,testsshowedthatmodestinternalgains(125W)willkeepbedroomswithin34F
ofthetemperatureofthecentrallivingspace. Atlowertemperatures,nearthedesign
temperatureof2F,ifroomshaveverymodestinternalgains,occupantsmaywanttoleave
bedroomdoorsopenoruseportableelectricheaters(verysparingly)tokeepupstairsbedroom
temperatureshigher.
Thespaceheatingsystemwillrequireadifferentlevelofresidentawareness. CARBhas
presentedinformation
to
residents
about
recommended
practices
(such
as
keeping
bedroom
doorsopenwhenunoccupied,avoidingextremedaytimetemperaturesetbacks,etc.). Onlyone
homewasoccupiedduringthewinterof20082009,andCARBwasnotabletomonitor
temperaturesthroughoutthishome. Forthewinterof20092010,fourhomeownershave
agreedtoletCARBmonitortemperaturesandinterviewthemaboutcomfortandenergyissues.
OnekeyresultinthecosteffectivenessofthesystemisthatRDIsavedapproximately$4,500on
mechanicalsystemsforeachhomewhencomparedtoaconventionalhomewithaboilerand
hydronicbaseboard
convectors.
Todate,resultshaveshownthatsimpleheatingsystemswithminimalornodistributioncan
effectivelyprovidecomfortinsomesuperinsulated,coldclimatehomes.
1.3. Gate Status
-
8/14/2019 SWA Report on WWSV Heating Systems
4/23
Table1. Stage1BGateCriteriaforNonDistributedHeatingSystemEvaluation.
2. Project Overview RDI Wisdom Way Solar Village
RDIsWisdomWaySolarVillageisdescribedinmoredetailinthecasestudyBuildingAmerica40+%
ColdInitialCommunityScale: RDIsWisdomWaySolarVillageupdatedinDecember2010. Thekey
featuresof
the
home
energy
systems
are
also
listed
here.
2.1. Plans
Thecommunityconsistsoftwentyhomesintenduplexesasoutlinedbelow:
Four2bedroom,onestoryhomes(1,137grossft2;twoofthesearefullyaccessible)
Four2bedroom,twostoryhomes(1,140grossft2)
Nine3bedroom,twostoryhomes(1,390grossft2)
Three4bedroom,twostoryhomes(1,773grossft2)
Thecommunitywasdesignedsothatallhomeshaveexcellentsolaraccessforbothpassiveand
activecollection. Plansforthethreebedroomhomeusedforshorttermtestingareincludedin
theAppendix.
2.2. Basement
"Must Meet" Gate Criteria No Go Recycle Go
1. Source Energy Savings and Whole Building BenefitsNew whole house system solutions must provide demonstrated source energy and
whole building performance benefits, including labor and material cost tradeoffs,
comfort, durability, reliability, health, ..., relative to current sys tem solutions based on
BA test and analysis results.
X
2. Performance-Based Code Approval
Must meet performance-based safety, health, and building code requirements for use in
new homes.
X
"Should Meet" Gate Criteria
1. Prescriptive-Based Code Approval
Should meet prescriptive safety, health, and building code requirements for use in newhomes.
X
2. Cost Advantage
Should provide strong potential for cost benefits relative to current systems within a
whole building context.
X
3. Reliability Advantage
Should meet reliability, durability, ease of operation, and net added value requirements
for use in new homes.
X
3. Manufacturer/Supplier/Builder Commitment
Should have sufficient logistical support (warranty, supply, installation, maintenance
support) to be used in prototype homes.
X
5. Gaps Analysis
Should include system's gaps analysis, lessons learned, and evaluation of major
technical and market barriers to achieving the targeted performance level.
X
-
8/14/2019 SWA Report on WWSV Heating Systems
5/23
wallfiveinchesinsideoftheloadbearing,exteriorwall. Fiberreinforcedpolyethylene(inthe
firsttwohomes)orinsulationnetting(inthelaterhomes)isstapledtotheinnerstuds,andthe
entire12
wall
cavity
is
filled
with
dry
blown
cellulose
insulation
at
densities
of
approximately
3.4lbm/ft3. WholewallRvalueisapproximately42ft2hrF/Btu.
Figure1. TypicalwallsectionfromAustinDesign,Inc.
2.4. Attic
Roofsofthehomeareconstructedwithmanufactured,raisedheeltrusses. Ventedattics
incorporatefullsoffitandridgeventsandfullinsulationbafflesateverytrussbay. Homesare
insulatedwith14oflooseblowncelluloseforanRvalueofapproximately50ft2hrF/Btu.
2.5. Windows
Onnorth,east,andwestfacades,RDIinstalledtriplepanewindows. Onthesouthernfacades,
highersolargaindoublepanewindowswereused. WindowpropertiesareshowninTable2.
Table2. WindowpropertiesattheWisdomWayVillage.U-value
2
-
8/14/2019 SWA Report on WWSV Heating Systems
6/23
2.6. Heating Systems
Thedesignheatloadsofthehomesareverysmalllessthan12,000Btu/hr. Withthevery
smallloads,
RDI
selected
avery
small,
simple
heating
system:
asealed
combustion,
natural
gas
firedroomheaterlocatedinthecentralareaonthefirstfloorofeveryunit. Theunitisa
MonitorProductsmodelGF1800;capacityis10,200Btu/hatlowfire,16,000Btu/honhighfire,
andtheAFUEis83%.
Figure2. Gasroomheaterinthelivingroomofthe3bedroomhometested.
Toalleviate
concerns
about
temperature
differentials
and
to
improve
ventilation
performance
CARBworkedwithRDItodesignaverysimpleairdistributionsystem. Thisisdescribedmore
intheVentilationSystemssectionbelow. Toassurecomfortinbathrooms,eachupstairs
bathroomcontainsasmall,500Wattelectricresistanceheater. Theelectricheatersarewired
toacranktimersotheycannotbeleftONforlongperiodsoftime.
2.7. Ventilation Systems
AswithmostofRDIshomes,theWisdomWaydwellingswilluseanexhaustonlyventilation
strategy.In
the
primary
bathroom
of
each
home,
aPanasonic
Whisper
Green
exhaust
fan
(modelno.FV08VKSL1)isinstalledandprogrammedtoruncontinuouslytomeetthewhole
buildingventilationrequirementsofASHRAEstandard62.22007(3060CFM,dependingonthe
unit). Thefanisalsoequippedtoboosttohighspeed(80CFM)foranadjustableamountof
timewhenthebathroomisinuse.
-
8/14/2019 SWA Report on WWSV Heating Systems
7/23
Figure3. Theexhaustfanandsimpleductdistributionsysteminstalledbetweenthefirstand
secondfloors.
2.8. Water Heating
Mostoftheenergyneedsfordomesticwaterheatinginthehomeswillbeprovidedbysolar
thermalsystems. Flatplatesolarcollectorsaremountedonthesouthernroofofeachhome,
andapropyleneglycolantifreezesolutioniscirculatedbetweenthecollectorsandaheat
exchangerlocated
in
astorage
tank
in
the
basement.
A
direct
current
pump
circulates
the
glycol;thepumpispoweredbyadedicatedPVmodule. Auxiliarywaterheatingineachhomeis
providedbyasealedcombustion,naturalgasfired,tanklesswaterheaterinstalledinthe
basementnearthesolartank.
2.9. Solar Electric Systems
Three andfourbedroomhomeshave3,420WattPVsystems,and2bedroomhomeshave
2,850Wattsystems. Overthecourseofayear,thelargersystemswillgenerateapproximately
3,750kWh;
the
smaller
systems
will
generate
3,125
kWh.
Benchmark
analyses
show
that
in
a3
bedroomunit,the3.4kWPVsystemwillprovide77%ofthehomeselectricalneeds.
3. Short-Term Testing
CARBworkedwithresearchersfromtheNationalRenewableEnergyLaboratory(NREL)toassessthe
performanceofatypicalthreebedroomhomeoneofthefirstthehomescompleted. Testingwas
performedduringoneweekinFebruary2009beforethehomewasoccupied.
3.1. Research Questions
ThefollowingresearchquestionsandgoalswereidentifiedbyCARBandNRELbeforethetesting
wasperformed.
1. Whatistheeffectiveleakageareaoftheunitasmeasuredwithablowerdoor? How
doestheleakageareachangewhentheadjacentunitisalsopressurized(guarded)? Do
-
8/14/2019 SWA Report on WWSV Heating Systems
8/23
ratesofthedistributionsystem? Whatarethepowerdrawsoftheventilationandair
distributionfansineachoperatingstate? Doallofthesequantitiesmeetthedesign
targets?
3. Whatarethetemperaturesinvariousroomsthroughouttheduplexoverconsecutive
24hourperiodswitheachoftheconditionsshowninTable3? Doesacentralpointin
eachroommeettheASHRAEStandard55comfortrecommendationsatvarioustimes
duringeachtest? DotemperaturedifferentialsbetweenroomsmeetACCAManualRS
guidelines(4Fmaximum)? Arethereanynoticeablehotorcoldspotsoninterior
surfacesasmeasuredusinganIRcamera?
Table3. Testmatrixformeasuringuniformityofheatingandoutsideairdistribution.
4. Usingoneunitoftheduplexasthetestspace,whatarethedifferencesinoutsideair
distribution(i.e.RAoA)throughouttheduplex,usingtheoperatingconditionsshownin
Table3?
3.2. Blower Door, Airflow, and Power Measurements
Totestenvelopeairleakage,CARBperformedblowerdoortestingoneachhalfoftheduplex
separatelyandcoincidentallytoassessleakagethroughthepartywall. Thethreebedroomunit
wheretheshorttermtestingwasperformedhadtotalenvelopeleakageof273CFMwhenthe
homewasdepressurizedto50Pa. Afivepointblowerdoorregressionshowedtotaleffective
leakagearea(ELA)of11.2in2. Whentheneighboringunitwasdepressurizedcoincidentally,
leakagedropped
by
40
CFM50
and
0.2
in
2
.With
such
low
party
wall
leakage,
researchers
concludedthattracergastestingandRAoAcalculationscouldbedoneeffectivelyinonlyone
halfoftheduplex. Significanttestingintheotherhalfwasnotpossibleasitwasalready
occupied.
TheHVAClayoutforthehometestedisincludedintheappendix. CARBmeasuredairflowand
Test
Case Doors
Ventilation
Fan
Distribution
Fan Notes
0 Closed Off Off Basecase;noventilation
1 Closed On On
2 Closed On Off
3 Closed On Off 1in2
openingineachbedroom
4 Open On On
5 Closed On On60Wlampineachbedroom. Notracer
gastests;tempmeasurementsonly.
-
8/14/2019 SWA Report on WWSV Heating Systems
9/23
3.3. Tracer Gas and Temperature Distribution Testing Procedure
Atsixpointsthroughoutthehome,NRELresearchersinstalledthermocoupleswithinradiation
shieldsat
4
above
the
floor.
A
simple
weather
station
also
measured
outdoor
air
temperature
andwindspeed. ThermocouplesandothersensorswerewiredtoaCampbellScientificCR10
datalogger,andconditionswererecordedat5minuteintervals.
Atthesamelocationofeachofthesixinteriorthermocouples(seeFigure4),NRELalsoinstalled
2.5mm(ID)polyethylenetubingthroughwhichairsamplesweredrawnevery12minutes. Air
sampleswererunthroughaBruelandKjaermodel1303multipointsamplerandmodel1302
multigasmonitor. Atthebeginningofeachtest,researchersintroducedasmallamountof
sulfurhexafluoride
(SF6)
into
the
home
and
distributed
it
evenly
through
all
spaces.
By
analyzing
theratesofdecayinSF6concentration,researcherswereabletocalculateeffectiveairchanges
ineachspace;moreaccurately,researcherscouldcalculatereciprocalageofair(RAoA,hr1)in
eachspace. Formoredetailsonthistestprocedure,seeNRELdocumentNREL/TP55031548,
ATestProtocolforRoomtoRoomDistributionofOutsideAirbyResidentialVentilation
Systems. Eachtestbeganatapproximately8:00AMandranforapproximately23hours.
Figure4. Sensorstandinonebedroomcontainingtracergassamplingpointandshielded
thermocouple. PhotofromNREL.
3.4. Air Distribution Results
Tracer gas tests performed ith all doors closed and the distrib tion fan t rned off (test case 2)
-
8/14/2019 SWA Report on WWSV Heating Systems
10/23
closed. Whendoorsareopen,thereisvirtuallynodifferenceinairchangerates. Inthistested
RDIhome,whenthedistributionfanwasturnedON(Case1),thevariationsinairchangerates
are
dramatically
reduced.
The
lowest
RAoA
is
again
in
the
northeast
bedroom
at
0.27
hr
1
,
but
thehighestvaluesinthekitchenandlivingroomisonly0.32hr1.
Basedontheseresults,CARBhasconcludedthatthissimpledistributionsystemmoving2530
CFMfromthecentralspacetoeachbedroomdoesindeedaddressconcernsaboutunequalair
changeratesindifferentpartsofthesehomes.
Whatremainsuncleariswhatrealimplicationsthatsuchvariationsinairchangerateshave.
Builders
like
RDI
have
used
exhaust
only
ventilation
in
hundreds
of
relatively
small,
efficient
homeswithnoapparentperformance,health,ordurabilityproblems. Ontheotherhand,when
bedroomsareoccupieddoorsareoftenclosed;receivinghalftheairchangesunderthese
circumstancesdoesnotseemideal. Itseemsthatthesimpledistributionsysteminthesehomes
seemstoaddressthisproblemquiteeffectively. CARBhopesthisresearchwillleadtogreater
understandingofthesesystems,butCARBbelievesmoreinvestigationisneededof
performanceissuesandIEQimplicationsofvariousventilationsystems. CARBalsohopesthat
theseinvestigationswilldrivedevelopmentofmoresmall,simple,lowcostmechanicalsystems
for
high
performance
homes.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
Case 1 Case 2 Case 3 Case 4
RAOA,
hr
1
AirChangeComparisons
LivingRoomKitchen
SWBRSEBRNEBRBath
-
8/14/2019 SWA Report on WWSV Heating Systems
11/23
3.5. Thermal Comfort Analysis and Results
3.5.1. Thermal Design Considerations
Thekeythermalcomfortconcerninthehomesiswintertemperaturesinupstairsbedrooms
thatarenotdirectlyheated. Whileloadsvaryfromroomtoroom,theaveragedesignloadofa
bedroomisapproximately1,500Btu/h(440W)withoutdoortemperaturesof2F. Asdesign
loadsgenerallyoccurduringthenight,solargainswerenotconsideredinthisanalysis.
Thesimpleheatingsystemreliesonmeetingthisloadinfourbasicways:
Internalgains(people,lights,electronics,etc.inbedrooms);
Natural
convection
air
moving
upstairs
from
a
warmer
downstairs;
Conductionthroughthefloorfromtheheatedspacesbelow;
Forcedconvectionfromthesmalldistributionsystem.
Internalgainswillvarytremendously. Asleepingpersonmaygiveoffapproximately60W,while
anawakepersonnotperformingrigorousexercisemaygenerate80100Watts. Avery
conservativeestimateforlightsandotherelectronics(TV,computer,alarmclock,stereo,
chargers,etc.)is45Wattswhileabedroomisoccupiedbyanawakeperson. Asanexample,a
bedroom
occupied
by
a
single,
awake
person
reading,
studying,
or
watching
TV
might
have
internalgainsof125W. Thisvalueisapproximately30%ofthedesignloadofthebedroom.
CARBbegancomputationalfluiddynamicsanalysis(CFD)toattempttoquantifyenergytransfer
fromnaturalconvectionwithinthehome. However,itsoonbecameapparentthatthe
quantitiesofheattransferredweresosmallandimpactoffactorssuchasresidenthabitswere
solargethathighuncertaintiesintheanalyseswouldmaketheresultsnexttomeaningless.
However,itispossibletoperformsimpleUAcalculationsonthefloorassemblybetweena
downstairs
space
(heated
directly)
and
an
upstairs
bedroom.
With
a
floor
area
of
160
ft
2
,
an
effectivefloorassemblyRvalueof3ft2hrF/Btu,andatemperaturedifferentialof7F,heat
conductionthroughthefloorassemblyisapproximately340Btu/hor100Watts. This
represents2025%ofthetypicaldesign load.
Notethatthetemperaturedifferentialinthiscalculationhastwoelements:
Upstairsbedroomairtemperatures(at4abovethefloor)of23Fcoolerthan
downstairsairtemperatureat4abovethefloor;
Airtemperatures
at
the
ceiling
of
the
first
floor
from
where
the
exhaust
fan
exhausts
of45Fhigherthanroomairtemperaturesat4feetfromthefloor. Duringthe
testing,CARBverifiedthatairattheceilingwasindeed45Fwarmer.
Thefinalheattransferelementisheatfromthesmalldistributionsystem. Usingthesame
temperaturedifferentialfromabove(7Ffromtheceilingofthefirstfloortotheaverage
-
8/14/2019 SWA Report on WWSV Heating Systems
12/23
Naturalconvection i.e.warmairrisingfromdownstairstoupstairswillprovide
significantheattobedrooms,especiallywhenbedroomdoorsareleftopen. Thiswas
not
quantified
during
design
stages;
Whenusedforsleeping,bedroomtemperaturesoflessthan6870Fareoftendesired
orconsideredacceptable;
Ifnotusedforsleeping,e.g.ifabedroomisusedasanofficeorstudy,internalgains
substantiallyhigherthanthe125Wattsusedintheexampleabovearelikely. Also,
designtemperaturesoccurinthenightorveryearlymorningnotwhenactivityinsuch
roomsishighest;
Finally,somesparinguseofportableelectricheatersmaybeusedunderextreme
conditions.
3.5.2. Thermal Comfort Test Results
TheweekoftestinginFebruary2009hadconsistentwinterweather: amixofcloudsandsun,
hightemperaturesinthe30sor40s,lowtemperaturesintheteensortwenties(F). When
CARBandNRELarrivedatthehome,theheaterthermostatwassettoapproximately50F;
researcherssetthetemperatureupto68F,butitrequiredalmost1012hoursbeforeupstairs
bedroomswerewithin4Fofdownstairstemperatures.
Plotsshowingtheresultsofthefourrelevanttestcasespertainingtotemperaturedistribution
areshownbelowinFigure6throughFigure9. Table4showsasummaryofthefinal
temperaturemeasurements. Thetableshowsairtemperaturesmeasuredat4:00AMduring
eachtest. Astestsbeganatapproximately8:00AMeachday,at4:00AMtestshadrun
approximately20hours,andoutdoortemperatureswereusuallynearthecoldestofeach24
hourperiod;CARBbelievesthesevaluesareasclosetosteadystateconditionsaspossible
duringthesetests.
Table4.
Summary
of
temperature
distribution
test
results.
Final
temperatures
were
recorded
at4:00AMofthedayofthetest,whenthetesthadbeenrunningapproximately20hoursand
outdoortemperatureswereneartheircoldest.
Test
Case Doors
Dist.
Fan Notes
Out
doors
Living&
Kitchen SEBR NEBR SWBR Bath
1 Closed On 17.3 68.9 65.4 63.1 66.4 64.1
2 Closed Off 34.8 70.6 61.8 60.6 62.7 63.7
4 Open On 23.7 69.1 65.9 65.9 66.6 65.7
5 Closed On60Wlampin
eachbedroom.26.6 68.1 66.3 65.0 67.4 64.6
"Final"Temperatures
-
8/14/2019 SWA Report on WWSV Heating Systems
13/23
Figure6. Plotshowingtemperaturesduringtestcase1. Alldoorsinthehomewereclosed,the
distributionfanwasrunning,andthesetpointoftheheaterinthelivingroomwas70F.
10
15
20
25
30
35
40
45
50
55
57
59
61
63
65
67
69
71
73
75
1
200
1
400
1
600
1
800
2
000
2
200
2
400
200
400
600
OutdoorT
emperature,
F
RoomT
em
perature,
F
Hour
RDI Room TemperaturesCase 1: Doors Closed, Distribution Fan On
Living
Kitchen
SE BR
NE BR
Bath
SW BR
Outside
10
15
20
25
30
35
40
45
50
55
57
59
61
63
65
67
69
71
73
75
OutdoorT
emperature,
F
RoomT
emperature,
F
RDI Room TemperaturesCase 2: Doors Closed, Distribution Fan Off
Living
Kitchen
SW BR
SE BRNE BR
Bath
Outside
-
8/14/2019 SWA Report on WWSV Heating Systems
14/23
Figure8. Plotshowingtemperaturesduringtestcase4. Alldoorsinthehomewereopen,the
distributionfanwasrunning,andthesetpointoftheheaterinthelivingroomwas70F.
10
15
20
25
30
35
40
45
50
55
57
59
61
63
65
67
69
71
73
75
800
1000
1200
1400
1600
1800
2000
2200
2400
200
400
600
Outdoor
Temperature,
F
RoomT
emperature,
F
Hour
RDI Room TemperatureCase 4: Doors Open, Distribution Fan On
Living
Kitchen
SW BR
SE BR
NE BR
Bath
Outside
10
15
20
25
30
35
40
45
50
55
57
59
61
63
65
67
69
71
73
75
Outdoo
rTemperature,
F
Room
Temperature,
F
RDI Room TemperaturesCase 5: Doors Closed, Distribution Fan On, 60W lights On
Living
Kitchen
SW BR
SE BR
NE BR
Bath
Outside
-
8/14/2019 SWA Report on WWSV Heating Systems
15/23
Whilethechartsoftemperatureresultsareinformativeinthemselves,CARBusedthetest
resultstocreateasimple,steadystateheattransfermodeltopredicttemperaturesin
bedrooms
under
varying
conditions.
The
variable
inputs
to
this
model
are
outdoor
temperature,
livingroomtemperature,internalgainsineachbedroom,andconditionofthebedroomdoors
(openorclosed). ThismodelwasbasedoncalculationssimilartothosedescribedinThermal
DesignConsiderationsabove,buttheassumptionswererefinedbasedonmeasurementsand
testresults. Thetestsalsoallowedapproximationsfornaturalconvectiveheattransferfrom
downstairstoupstairsbedrooms(whichvariedtremendouslywhendoorswereopenorclosed).
Whilethemodelisverysimple,ithashelpedCARBpredictthermalcomfortundervarious
conditionsanddeveloprecommendationsforRDIandhomeresidents.
Severalexampleresultsofthesteadystatemodelareshownbelow. Thefirst,inTable5,shows
conditionssimilartotestconditions1and4(seeTable4). Inthisscenario,theunoccupied
northeastandsoutheastbedroomswithdoorsclosedwouldbemorethan4Fcoolerthan
thedownstairsspace(this4FtoleranceisusedincomfortstandardssuchasACCAManualRS).
Table5. OutputofCARBssteadystateheattransfermodelpredictingbedroomtemperatures.
Theexample
shown
in
Table
6parallels
test
case
5,
where
a60
Watt
lamp
was
lit
in
each
bedroomtosimulateasingle,sleepingperson. Theeffectsofsuchasmallloadarenoticeable
(seeFigure9aswell),butthetemperatureinthenortheastbedroom(withdoorsclosed)isstill
morethan4Flowerthanthecentralspacedownstairs.
Table6. OutputofCARBssteadystateheattransfermodelpredictingbedroomtemperatures.
Downstairs Temp: 70 F
Outdoor Temp: 20 FInternal Gains: 0 Watts
SW BR SE BR NE BR
Doors Closed 67F 65F 63F
Doors Open 68F 67F 66F
Downstairs Temp: 70 F
Outdoor Temp: 20 FInternal Gains: 60 Watts
SW BR SE BR NE BR
Doors Closed 69F 68F 65F
D O 70F 69F 68F
-
8/14/2019 SWA Report on WWSV Heating Systems
16/23
Table7. OutputofCARBssteadystateheattransfermodelpredictingbedroomtemperatures.
Ofcourse,20FisnotthedesigntemperatureinGreenfield,MA;the99%designtemperatureis
2F. Undertheinteriorloadconditionswith2Foutdoortemperature,Table8showsthatair
temperatureinthenortheastbedroomwithdoorsclosedisagainpredictedtobemorethan
4Fbelowtheairtemperaturedownstairs.
Table8. OutputofCARBssteadystateheattransfermodelpredictingbedroomtemperatures.
Underdesign
conditions,
the
model
shows
that
with
internal
gains
of
only
200
Watts
the
bedroomtemperaturesarenotmorethan2Fbelowthedownstairsairtemperature(seeTable
9). Suchgainsarenotatalluncommoninoccupiedroomswherecomputerequipment,audio
equipment,ortelevisionsarebeingused. Insomecaseswhenoutdoortemperaturesarevery
lowandinternalgainsaremodest,residentsmayusesmallelectricresistanceheatersforshort
periodsoftimetomakeupthisdifference.
Table9. OutputofCARBssteadystateheattransfermodelpredictingbedroomtemperatures.
Downstairs Temp: 70 F
Outdoor Temp: 20 F
Internal Gains: 120 Watts
SW BR SE BR NE BR
Doors Closed 72F 70F 68F
Doors Open 72F 70F 70F
Downstairs Temp: 70 F
Outdoor Temp: 2 FInternal Gains: 120 Watts
SW BR SE BR NE BR
Doors Closed 69F 67F 64F
Doors Open 70F 68F 67F
Downstairs Temp: 70 F
Outdoor Temp: 2 F
Internal Gains: 200 Watts
SW BR SE BR NE BR
-
8/14/2019 SWA Report on WWSV Heating Systems
17/23
3.6. Recommendations to Residents
SWAhaspresentedasummaryofthesetestresultstohomebuyersandfoundthemquite
interestedand
receptive
though
they
were
certainly
most
excited
about
the
extremely
low
energycostsexpected. SWAhasalsoprovidedmaterialtoRDIforthehomeownersmanualson
recommendationsforoperatingandstayingcomfortableinthesehomes. Briefly,the
recommendationsinclude:
Comfortispersonal;neighborsmaybecomfortableunderverydifferentconditions.
Onceroomsarewarm,theytendtostaywarm. However,coldbedroomsmaytake
severalhourstofullyheatup.
Werecommendagainstextremedaytimethermostatsetback. Recoverymaybeslow,
andenergy
savings
are
minimal
for
two
reasons:
o Verylowenvelopeheatloss.
o Duringsunnydays,theheaterdoesnotneedtorun.
Ifyoudousedaytimesetback,makesetbackssmallandstartincreasingtemperatures
early.
Itisworthsettingthetemperaturedownifleavingforseveraldays.
Youmayalsowanttolowertemperaturesslightlyatnightforsleeping.
Keepbedroomdoorsopenwhennotoccupied.
Itspossible
that
sparing
use
of
small,
inexpensive
electric
heaters
may
be
desirable.
Oncearoomiswarm,heatersshouldntbeneededexceptunderextremelycold
conditions.
Duringcoldestweather,keepingdownstairsattheupperendofcomfortrange(7072F,
ratherthan6668F)willkeepbedroomswarmer.
Learnwhatworksbestforyou.
4. Long-Term Monitoring and Evaluation
Duringthe
winter
of
2009
2010,
CARB
has
made
agreements
with
residents
of
four
homes
to
record
temperatureandhumidityconditionsatseverallocationsineachhome. Temperaturesineach
bedroom,thecentrallivingspaces,andoutdoorsarebeingrecordedat10minuteintervalsthroughout
thewinter. Inthespring,CARBwillalsointerviewresidentstodetermine:
Howtheygenerallyusedeachspace;
Theirimpressionsofcomfortconditionsinvariousspaces;
Whatpracticestheyusedtostaycomfortable(opendoors,thermostatsetbacks,spaceheaters,
etc.);
OtherfeedbackorerecommendationsrelatedtotheperformanceoftheHVACsystems.
CARBfeelsthatlongtermmonitoringofoccupiedhomesalongwithfeedbackfromresidentsis
criticaltoaccurateassessmentofthisHVACstrategy.
5. Gate Criteria
-
8/14/2019 SWA Report on WWSV Heating Systems
18/23
equipment. CondensinggasroomheatersareavailableinEurope;theymaybecomemore
availableintheUSsoon.
5.1.2. Performance-Based Code Approval
Therewerenocodeissueseitherperformanceorprescriptiveencounteredrelatedtothe
mechanicalsystemsinthesehomes.
5.2. Should Meet Criteria
5.2.1. Prescriptive Code Approval
Therewerenocodeissueseitherperformanceorprescriptiveencounteredrelatedtothe
mechanical
systems
in
the
homes.
5.2.2. Cost Advantage
Thecostsavingsistheprimarybenefitofthistypeofsimplemechanicalsystem. Inthese
homes,thesimpleheatingsystemsavedRDIapproximately$4,500(whencomparedtotheir
standardsystemofaboilerwithbaseboardconvectors). Thissubstantialsavingswentalong
waytooffsettheadditional$6,050spentinthermalenvelopeimprovementsineachhome.
5.2.3. Reliability Advantage
Theoperation
and
maintenance
of
sealed
combustion,
gas
fired
room
heaters
is
generally
simplerthanmaintenancerequiredoncentralfurnaces. Thesedeviceshavebeenavailableand
inusefordecades;theysimplyhavenotoftenbeentheprimaryheatsourceforanentirehome.
CARBfeelsthatthisreliabilitycriterionhasnotyetbeenfullyaddressedbecauseofthelackof
documentationofcomfortconditionsinoccupiedhomes. Afterthewinterof20092010,CARB
hopestohavedatatomorefullyaddressthiscriterion.
5.2.4. Manufacturer/Supplier/Builder CommitmentTherearenomanufacturerorsupplierissuesrelatedtothistechnology. Theseroomheaters
arereadilyavailablefromseveraldifferentmanufacturers. CARBhasalsoheardreportsofmore
modelsandmoreefficientmodelsbecomingavailable.
Regardingbuildercommitment,aslongascomfortandreliabilityisaddressed,RDIiscertainly
opentousingsimilarsystemsinfutureprojects. Withthesignificantpublicitythatthisproject
hasachieved,therehavebeenseveralotherbuildersanddeveloperswhohaveexpressed
interestin
such
simple
mechanical
systems.
5.2.5. Gaps Analysis
5.2.5.1 Comfort
Asdescribedabove,comfortinbedrooms(withoutdirectheat)isoneofthelargestconcerns
i h hi B d d li d h i CARB b li h f ill b
-
8/14/2019 SWA Report on WWSV Heating Systems
19/23
threesmall,pointsourceheaters(gasroomheaters,minisplitheatpumps,etc.)ratherthana
conventionaldistributedHVACsystem. Implicationsforlargerhomesneedtobeinvestigated
further.
5.2.5.3 VentilationAirDistribution
Thesmall,simpledistributionsysteminstalledinthesehomescombinedwiththeexhaustonly
ventilationsystemappearedtoaddressvariationsinairchangeratesinallspaceswhendoors
areclosed. However,thereisstillaquestionaboutperformanceofexhaustonlyventilation
withoutsuchadistributionsystem.
Inaddition,thedistributionsystemusesanexhaustfan. CARBhastalkedtoseveralHVAC
equipmentmanufacturers
about
adistribution
fan
of
similar
size
and
power
consumption
but
withpotentialforairfiltrationandpossiblyevenauxiliaryresistanceheat. Forlargerhomes,
slightlylargerfansmaybeappropriate. Asthisisrelativelynewterritory,CARBbelievesagreat
dealmoreinvestigationisneededintoappropriateapplicationsandequipmentforsuchsmall,
simpleairsystems.
6. Discussion and Conclusions to Date
HomeslikethesethatarereallyapproachingzeroenergyareforcingaparadigmshiftinHVAC
systems.There
are
simply
no
conventional
heating
systems
sized
to
meet
these
small
loads.
Also,
as
shownabove,typicalinternalgainsinbedroomsareonthesameorderofmagnitudeasheatlost
throughtheenvelope. Notonlywouldanyconventionalfurnaceorboilercapacitybethreetimesthe
sizeofthedesignloadofthesehomes,unlesseachbedroomwasaseparatezone,aconventional
systemwouldalsonotaccountforvaryinginternalgainsinbedrooms;thiscouldfrequentlyresultin
overheatingofspaceswithoutathermostat.
Withtheinvestigationsdonetodate,SWAbelievesthissimple,efficient,lowcost,lowmaintenance
HVACsystem
will
provide
comfort
as
good
if
not
better
than
aconventional
system
(such
as
acentral
gasfurnace). Theonehomeownerwhooccupiedahomeduringthewinterof20082009saidtherewas
noneedforauxiliaryheatinbedrooms;theystayedcomfortable. Monitoringandinterviewsfromthe
winterof20092010willshedmorelightoncomfortandperformanceissuesinthehomes.
Ifperformanceresultscontinuetobepositive,CARBbelievesthatsmall,simpleHVACsystemscanoffer
tremendouscostsavingsinhighperformancehomesatleastpartiallyoffsettingthecostofsuper
insulatedenvelopes. IntheseRDIhomes,theaddedthermalenvelopefeaturescostRDIapproximately
$6,050(when
compared
to
their
standard
construction:
2x6
walls
with
blown
cellulose,
double
pane
windows,R38attics). Withthesimplemechanicalsystems,RDIsavedapproximately$4,500when
comparedtotheirconventionalheatingsystem(boilerwithhydronicbaseboardconvectors). Such
savingscanbetremendouslyhelpfulinachievingBuildingAmericaperformancegoalscosteffectively.
-
8/14/2019 SWA Report on WWSV Heating Systems
20/23
-
8/14/2019 SWA Report on WWSV Heating Systems
21/23
-
8/14/2019 SWA Report on WWSV Heating Systems
22/23
-
8/14/2019 SWA Report on WWSV Heating Systems
23/23