......---. - --- -----------Energy Principles in Architectural
DesignLegal Notice: This report wasprepared asthe result of
worksponsored bythe CaliforniaEnergy Commission. It does
notnecessarily represent the views ofthe Energy Commission,
itsem-ployees, or the State of California.The Commission, the State
of Cal-ifornia, itsemployees, contractors,andsubcontractors make
nowar-ranty, express orimplied, andas-sume nolegal liability for
the in-formation in this report; nor doesanyparty represent that
theuseof this information will not in-fringeupon privately
ownedrights.4,EnergyPrinciples in Architectural DesignWritten
andIllustrated by EdwardDeanShelley Dean andFuller,
ArchitectsArchitecture, Planning, Energy
ConsultingOakland/Berkeley, CaliforniaCaliforniaEnergyCommissionIn
cooperation withTheCalifornia Boardof Architectural ExaminersThis
bookwas prepared under acontract fromthe CaliforniaEnergy
Commission, ConservationDivision, 1111HoweAvenue,Sacramento,
California, 95825.First Printing: 1981, bytheCalifornia Energy
Commission.All rights reserved.ForewordThis text was developed
fortheCalifornia Board of ArchitecturalExaminers foruseasa
studyguidebyapplicants for theCalifornia license
topracticearchitecture.The intent ofthis bookistoprovide
afoundation of basic in-formation pertaining todesignandenergy use
in buildings. Theideaisthat the reader will beablebothto seek out
more detailedtexts in the various topicareasandtobecome aware of
potentialapplications ofnewresearch andproduct development in the
com-ingyears. Inaccordance withthisobjective, the emphasis
isonprin-ciples andconcepts rather thanapplications of particular
solu-tions. Energy isclearly anarea ofemerging possibilities in
buildingdesign, andsolutions that areappropriate orworkable
nowarelikelytobelessattractive thanfuture alternatives.Wehope that
the notionof thisconceptual approach toenergyandbuilding design
will encour-agesome architects to undertakethe difficult reading
inmore tech-nical texts andjournals, andulti-mately tomake the
kinds of need-edcontributions in this fieldthatonlyarchitects
canprovide.vVIAcknowledgmentsToHal Levin, member of theCalifornia
Board of ArchitecturalExaminers, whose personal
en-ergyandcommitment toenergy-responsive design ledtothedevelopment
of this book.ToSung Chough, D.C. Berkeley,for helping withsome of
the il-lustrations.ToEugene Mallette andJoseMartinez of the
California EnergyCommission for their timely sup-port.Tothe members
of AlA, CALBO,whoreviewed the original manu-script andprovided
helpful sug-gestions.ToEdward Allen, whose recentbook, HowBuildings
Work, pro-vided the excellent model for ex-plaining technical
concepts in athoroughly understandable man~neroTomyassociates,
familyandfriends for their support
anden-couragement.ContentsForewordAcknowledgments1. Fundamentals of
Energyand BuildingMaterialsIntroductionEnergy Use andPower
DemandEnergy Transfer MechanismsEnergy Storage in
BuildingMaterials2. SitePlanningand SiteDesignEnergy Impacts of
Landforms andTopographyEnergy Impacts of VegetationEnergy Impacts
of WindandVentilationEnergy Impacts of Sun3.
BuildingEnvelopeDesignGeneral DesignConsiderationsPassive Systems:
HeatingPassive Systems: CoolingPassive Systems: Lighting4.
BuildingActiveSystems DesignHeating
SystemsCoolingSystemsHVACSystemsLighting
SystemsBibliographyIndexvVI1262024252627313849505964667173831.Fundamentals
of Energy and BuildingMaterialsII1IIIIn troductionBefore
considering the technicalaspects of energy use in buildings,it
isimportant tounderstand thatthe demand for energy in build-ings
isnot duetothe character-isticdesignof thebuildingen-velope orthe
use of mechanicalsystems per se, but the users'subjective
requirements forper-sonal comfort. People controltheir thermal
andlighting en-vironments tosuit their needsbased onpatterns of
culture, geo-graphic region, age andpersonallifestyle.
Givenaparticular set ofthese social factors, variation inpersonal
comfort requirementsstill occurs because of individualdifferences
in activity andper-sonal preference. The level ofenergy use in
anybuilding ulti-mately depends onthe choicesmade bythe people
whooccupyandoperate it.TT nderstanding these variationsiil user
demand isimportant sincethe acceptable range of comfortvariables
establishes a certain de-signperformance specification forthe
building. Often the designercaninclude a certain
flexibilityandlocal control of energy sys-tems that allowfor these
varia-tions, andwhichasa result helpreduce overall energy
consump-tionlevels.Conditions that yielda comfor-table environment
involve a com-bination of several related var-iables that
couldbemodifiedseparately tomaintain comfort.1-3Thermal comfort,
for example,depends primarily onair temper-ature, humidity, air
movement2-82231 12andthe temperature of the sur-faces surrounding
the person. Theperceived comfort range of indoorair temperature
canbeenlargedbyproviding warmsurfaces thatreduce aperson's heat
losstothesurrounding environment. That is,people will findthat
theyare com-fortable at lower air temperaturesif the surrounding
surfaces arewarmer. Likewise, for conditionsof highair temperature
peoplemayfeel comfortable if theyarenear coolsurfaces. This
expansionof the comfortzone, the range oftemperature andhumidity
thatmost people experience asa com-fortable condition, usually
resultsin lower energy comsumption inthe building.Fromanenergy
point of view,the building should generally bethought ofas'
apassive moderatorof energy flows, designed to~Iachieve the most
comfortable con-ditions, both thermally andvisual-ly, for the
particular user groupandbuilding program.This important point
havingbeen mentioned first, the remain-ingsections of this chapter
treatthe basic technical concepts ofenergy andbuilding
materials.EnergyUseand PowerDemandEnergy isdefined asthe"capacity
todo work", whilepower isthe rate at whichenergyisused. For most
building designapplications, both energy useandpower demand should
beconsid-ered fromthe beginning of thedesign process.Energy appears
in severalforms-heat, light, electrical,mechanical etc., -and
canbetransferred orstored.HeatHeat energy canbestored in amaterial
ortransferred toanothermaterial bya variety of methods.The basic
driving force behind allthe mechanisms of heat
transferfromonematerial toanother isthe temperature difference
be-tween the two. It should bere-membered that temperature isnotthe
measure ofheat content of amaterial but, relative toasecondobject's
temperature, isa measureof heat flowfromonetotheother. The units of
temperatureare either degrees Fahrenheit (OF)ordegrees Centigrade
(Dc) ..Heat will not spontaneouslytransfer fromonematerial
toanother at higher temperature, sothe direction of heat
flowisalways fromthe material at thehigher temperature tothe
mate-rial at the lower temperature. Inorder totransfer heat toa
ma-terial at a higher temperature, asinthe case of a refrigeration
ma-chine or roomair conditioner,energy fromanexternal sourcemust
beapplied.The units of measurement ofheat energy are commonly
theBtuandthe kilojoule (metric).OneBtuisdefined asthe amountof heat
required toraise the tem-perature of onepound of water byonedegree
Fahrenheit. (The kilo-joule isapproximately the samequantity of
heat energy astheBtu: 1 kj = 0.95Btu.) Inonehour,for example,
a60-watt light bulbreleases approximately 200Btuofheat
energy.LightLight has always been regardedasa principal element of
architec-tural design, frombotha visualandspatial point of view,
andfromaconcern for user needs anduser comfort. The needfor
ener-gyconservation andcontrol ofpeak electric power demand
inbuildings nowrequires a morecareful consideration of
thefunctional requirements of light-ing, especially
asdaylightingtechniques are integrated intolighting design.Onemajor
requirement issim-plythe amount of light availablefora givenvisual
task. Light en-ergyismeasured inlumens. Onelumenisdefined asthe
amount oflight energy fromasource of in-tensity onecandela (1
candle-power), incident ona unit area ata unit distance fromthe
source.Thefootcandle andthe lux (metric)are measures of
illumination. Onefootcandle is the amount of il-lumination provided
byonelumen1 footcandleof light energy incident onaone-square-foot
surface. Oneluxisequivalent toonelumenpersquare meter.
(Onefootcandle isabout the same as 10 lux, sothenumber of
luxequivalent toacer-tainfootcandle level canbedeter-mined
bymultiplying by10.Therefore 50fcis approximately500lux.)Visual
comfort isa primarycondition of the success of anylighting scheme
designed tomini-mize electrical demand.4 The fac-tors that
determine visual comfortinclude not onlythe amount oflight energy
available foraspeci-ficvisual task, but alsothe direc-tionof the
light relative totheeye, the brightness of objects sur-rounding the
task object andwith-in the fieldof view, andthe sur-facereflectance
andlight-dif-fusing characteristics of the taskobject.5
Agoodlighting designoptimizes these factors forvisualcomfort,
andcanbeexpected toresult inmaximumenergy conser-100 footcandles60
wnttsj!10,000footcandles3Energy Equivalences andEnergy-Rate
EquivalencesEnergy Equivalences Energy-Rate Equivalences1 Btu=0.293
watt-hr 1 watt = 3.413Btu/hr3413Btu = 1 kilowatt-hr 1 kilowatt =
3413Btu/hr100,000 Btu = 1 therm 1 horsepower = 3/4Kw1015Btu = 1
quad 1 tonof refrigeration = 12,000Btu/hr4vation aswell. Onthe
other hand,failure tocontrol glare andotheruncomfortable conditions
canre-sult in higher energy consumptionlevels than expected, since
theuser islikelytoovercome lightimbalances byusing
availableelectrical light sources.Inshort, energy
conservationthrough efficient lighting designinvolves much more
than simplyprescribing "task lighting" orlimiting the amount of
light avail-able per task. Indeed, these sim-plistic approaches are
likelytobecounterproductive in the absenceof a total design
approach.PowerThe concept ofthe power de-mand of a building
isanextreme-ly important aspect of energy-efficient design. Load
manage-ment aspects of building designbecome more significant for
larg-er buildings, andfor utility serv-iceareas with "inverted"
ratestructures where the buildingowner is billedat
successivelyhigher rates for higher levels ofpeak electrical power
demand. Inthese instances design strategiesshould have the
objective of re-ducing both the energy consump-tionover the annual
operation cy-cleof the building andthe peakp0wer demand under peak
loadconditions.Power differs fromenergy inthat power isthe rate at
whichenergy is used. Inthe metricsystem, the unit of power is
thewatt, and 1000watts isequal toonekilowatt. The common unit
ofpower inthe English (American).system isthe horsepower.
Onehorsepower is equal toabout 3/4of a kilowatt.Design strategies
that minimizeelectric power demand in build-ings, andthat
avoidunnecessaryuse of electric power for heatingandcooling in
spite of the advan-tages of smaller initial costs orsimpler
installation of equipment,will provide amoreenergy-efficient
overall building stock. Inthe first place, utilizing "highquality"
energy (electricity) foraJIJ,.I"lowquality" energy
application(heating or cooling) is wastefulandinefficient.
Inaddition, the"real" conversion efficiency ofelectric energy is
low for theseapplications compared to alterna-tivemethods.
Approximately two-thirds of the energy usedbyatypical power plant
to generateelectricity foramodern Californiaofficebuilding islost
aswasteheat.5.7 Therefore, onlyone-thirdof the original energy
availablegoes to heat andilluminate thebuilding. This isa"real"
effi-ciencyof onlyabout 33percent.(This "typical" power plant
isaweighted average of hydro, fossil,nuclear andgeothermal
powerplants in California andrepresentstheaverage conversion
factoradopted bythe California EnergyCommission aspart of the
StateEnergy Conservation Standards. 7)Finally, the design effect of
un-necessary electric power demandcreates a supply problemthatmust
bemet, if possible, bycapi-tal investment in newpowerplants withthe
concomitant econ-omic, social andenvironmentalimpacts.The advantage
of initial costsavings byusing electric heatingshouldalways
beweighed againstthe serious disadvantages of high-eroperating
cost, lowconversionefficiency, andincreased demandforcapital
investment innewpower plants byCalifornia
utili-ties.5EnergyTransferMechanismsTheNature of Solar EnergyThe
sunis anefficient source ofheat andillumination forbuild-ings,
andisthe single most impor-tant natural element toconsider
inbuilding design. The problemfordesigners isthat the amount ofheat
andlight fromthe sunismuch larger than necessary forcomfortable
conditions. Inthepast, the simple solution hasbeentoexclude the
solar input asmuchaspossible andtorelyonbuildingsystems for control
of heating,ventilation andillumination. Nowgreater skill isdemanded
ofthedesigner toutilize this free energyasmuchaspossible.Solar
energy arrives at theearth's surface at the rate ofabout 200Btu/hr
per square footof surface perpendicular tothe di-rection ofthe sun.
This isequal toabout 60watts per square foot.This sunlight isin the
formofra-diant energy in arange of"wave-lengths". That portion of
the sun-light visible tothe human eyeisshort-wave radiant energy.
Ther-mal radiation (known asradiantheat)islong-wave radiant
energy.About half of the energy in sun-light isvisible light
(short-waveradiant energy). This light energyamounts to about
7500lumens atthe earth's surface on aclear day.The ratio or the
number of lu-mens produced bya light sourcetothe power output in
watts, aratio known asthe "efficacy" ofthe light source, isameasure
ofthe efficiency of that source. Forsunlight, the lumen/watt ratio
isapproximately 7500/60=120.8Bycomparison, a40-watt incandes-cent
lamp produces about 480lu-mens for anefficacy of12,whilea 40-watt
fluorescent lampcanproduce about 2640lumens for anefficacy of 66.
This means thatfluorescent lamps are about fivetimes
asenergy-efficient asin-candescent lamps-that is, one-fifthof the
power wattage isre-quired toprovide the same
bright-r-adiowO,ves-0I100150
100~,I~I,,-t'"',i;1'j"...I10.0mdicmtheatradiantheC1t"..... - .. . .
.." .. " .... ', ' '/' cI?ti1ysky ,, '-'I1.0\/Isiblelight}E->\,
I0.5 1.0 5.0 10\Ncwe \enqth(millionths
of'dmete-f)Wavelength(m'dlionthsofa meter)The Solar
Spectrum0.1~0,16450Iumens/ 40WC1ttS\' \\\ 11////\\ \\",11////cc--
[@::1//1/ II / II \ \ \ \ \ \ ~/ ( I \ \2640 lumens/4Oworts~s~///
~// I! \ \\ \ \~,5000lumens/4O WC\tts~Iness level. Yet fluorescent
lampsare onlyabout halfasefficient asthe sun. The implication for
de-signers is that daylighting, if pro-perly done, will not
onlyreduceelectric energy consumption forlighting, but should
minimizeloads on air-conditioning equip-ment. Infact, in many
situationstheair conditioning loadfromdaylighting should
belessthanthat fromacomparable fluores-cent lighting system. Solar
energyshould therefore bethought of asbotha heat source
andalightsource forbuildings, although avariable one.When solar
energy strikesbuilding surfaces, certain
energyflowsandtransformations occur.Energy flowsin the
environmentinvolve a complex set of energytransfer mechanisms that
interacttoproduce a givenset of environ-mental conditions. The
designer'stask istocontrol andplanthecombination of these
interactionsin order toproduce aset of condi-tions that requires
the leastamount of outside energy for com-fort. Inorder tomanage
this com-binant energy flow, it is necessaryto understand the
characteristicsof eachof the individual heattransfer mechanisms,
namely, ra-diation, convection,
conductionandevaporation.7Absorptance andReflectance of Common
GroundMaterials(expressed asfraction of total incident solar
energy)AbsorptanceReflectanceWater0.9 0.1DryGrass0.7 0.3DrySoil0.8
0.2Asphalt0.9 0.1Concrete.:;:.l;:0.60.4Snow0.1-0.2
0.9-0.8LowShrubs0.7 0.3Sand0.8 0.28Thermal RadiationThermal
radiation isradiantheat, emitted byall warmed ma-terials. The
higher the tempera-ture of amaterial, the more ra-diant heat
isemitted. The warmthfelt fromanasphalt parking lot onasunny day,
fromanordinarycampfire andso-called "bodyheat" are allexamples of
thermalradiation. The amount of thermalradiation given off bya
normallyclothed person at rest is about200Btu/hr, orthe equivalent
ofthe heat radiated bya60-wattbulb.Thermal radiation
islikelightenergy: incident radiant energycanbeabsorbed, reflected
ortransmitted byamaterial. Thethree material properties asso-ciated
with these processes are,respectively, absorptance, reflec-tance
andtransmittance. The ab-sorptance isthe fraction of inci-dent
energy that iscaptured andcauses atemperature increase ofthe
material. The reflectance isthefraction that isdeflected at
thesurface of the material andcausesnochange intemperature.
Thetransmittance isthe fraction thatpasses through the material
andhas noeffect onthe material. Thesumof these fractions must
equal1.0 since allthe incident energymust beabsorbed, reflected
ortransmitted. Animportant fact isthat these fractions canhave
dif-ferent values for different wave-lenths of radiant energy.
White-painted surfaces, for instance,have a very low absorptance
ofshort-wave solar energy but avery highabsorptance of long- .wave
radiant heat.Bydefinition opaque materialshave atransmittance equal
tozero, soanyenergy not reflectedisabsorbed. The accompanyingtable
lists some common groundandbuilding materials andgivestheir
absorptance andreflectancecharacteristics for solar energy.Ground
materials near buildingswithahighabsorptance for solarenergy anda
relatively lowther-mal capacity, suchasblack as-phalt, will cause
heat
toaccumu-----------------------------~~~--------------------~~~~~--~~--~-~\\!/
~\l// ~~_!"~~~UJ >.~ ~ // ~.~~~~ ~ ~ //~ -./'" ,/ // It;" :
,/highemmc:mce high emittcmce loweml\ranceRadiant Heo.thigh
absorptqnce low obsorptanceSola, Energylatearound buildings.
Ontheother hand, material suchasgrassy soil andplants,
whichhavesome reflective characteristics anda higher thermal
capacity, willkeep air temperatures downaround buildings
andprovidesome additional freehumidity.Anadditional property of
con-struction materials, known asemittance, is ameasure of the
abil-ityof amaterial toradiate heat.For a specificwavelength of
ra-diant energy the emittance isequal to theabsorptance. The
sec-ondtable lists the absorptance,emittance andreflectance
valuesforsomecommon building mate-rialsforbothshort-wave
solarenergy (primarily visiblelight) andlong-wave radiant heat.
Some im-portant facts about energy flowinbuildings canbeobserved.
Note,forinstance, that most opaquebuilding materials are
absorptive.of solar energy unless
deliberatelylight-orwhite-colored. Inthe lat-ter casetheybecome
quite reflec-tiveof the sun's energy. Thischaracteristic
isdesirable forbuildingwalls androofs in thedesert andvalleyregions
of)II1iIEnergy Characteristics oftheSurfaces of Common Building
MaterialsSolar EnergyRadiant HeatAbsorptanceReflectance Emittance
Reflectance(& Absorptance)White-painted Walls0.15 0.85 0.90
0.10Green-painted Walls0.50 0.500.90 0.10"".Black-painted Walls0.90
0.10 0.90 0.10Green RollRoofing0.90 0.10 0.90 0.10RedBrick0.55 0.45
0.90 0.10Concrete (fresh)0.60 0.40 0.90 0.10Asbestos Cement
Board0.60 0.40 0.95 0.05Sheet Metal (Shiny)0.20 0.80 0.20
0.80Polished Aluminum0.10 0.90 0.10 0.903-8223191~11111111111111111
~ll ~IIIIIIII~IIII ~IIIIII!II! I1III110blockCalifornia, but not
necessarily inthe coastal areas andother clima-ticregions where
significantheating mayberequired. Intheseregions the material onthe
sur-face of the south wall should havea dark-colored surface for
max-imumsolar absorption in winter.Another feature isthat
white-painted surfaces andblack-paintedsurfaces have the same
emittancevalues for long-wave radiant heat.Therefore, the interior
surfaces ofmasswall passive systems (de-scribed inchapter 4)
canbepainted white without suppressingthe radiation of heat.
Likewise, inahot climate where heating isnotamaj"or concern, a
white roof hasthe double advantage of having ahighreflectance of
the short-wavesunlight and, during the nightwhen the skyisclear
andrelative-ly cold, of having a highemit-tance (0.9)of the
long-wave ra-diant heat built upinternallyduring the day. The
latter processisknown asnocturnal radiationcooling.Afurther
observation in this re-gard is that the emittance of po-lished
metal surfaces remains lowfor both solar energy andradiantheat.
Suchmaterials used onroofs, for instance, tend tosup-press radiant
heat losstothe sky,animportant concern in areas ofclear, coldwinter
climate condi-tions.Glass isa material that isgen-erally
highlytransmissive ofshort-wave solar radiation (visiblelight),
although absorption andre-flection alsotake place toa smalldegree.
However, glass has are-markable property relative tolong-wave
thermal radiation-thatthe transmittance for thermalradiation
iszeroandthe absorp-tionispractically equal toone.This
characteristic isillustrated inthe accompanying figure whichshows
the transmittance of glassfor different wavelengths of ra-diant
energy, andthe wavelengthspectrum of both incident solarenergy anda
hypothetical warmedbuilding mass. The radiant heatemitted bythe
mass haswave-lengths inthe region where glasshas zerotransmittance.
Thephenomenon experienced asa re-I..".IJj;-'16Il10100o.J0.1visible
rod iantlighthear~I(>', I,I II II1.0 10Wave\en~th(millionthsaa
meter) 3> (j)ocE
