PEAK D£i"IAND SAVINGS FROM DAYLIGHTING Ir~ COIYlMERCIAl BUILDINGS

s~ Selkowitz, D. Arasteh, and R. JohnsonEnergy Efficient Buildings Program

Lawrence Berkeley Laboratory

ABSTRACT

In many regions in the U.S~, load management and peak demand issuesare of greater importance to utility planners than are reductions inenergy consumption~ Proper daylight utilization in commercial buildingscan substantially reduce peak demand and increase energy savings. How­ever, to determine optimum design strategies for controlling electricaldemand~ it is first necessary to understand the often conflictingimpacts of fenestration on lighting and cooling loads. We use an hour­by .... hour energy simulation model (DOE-291B) to evaluate peak demand corn­ponents and net effects in daylighted and nondaylighted buildings. Morethan 5000 parametric simulations were generated for prototypical officebuilding modules containing both horizontal and vertical glazing, andlocated in 16 U.S. cities. From these si,nulations we draw conclusionsabout the effects of daylighting on peak demand for a range of climatetypes, orientations, fenestration areas, glazing shading coefficientsand vi e transmittances, U-values, lighting power densities, andlighting control strategies~ Results for Los Angeles are briefly corn­pared to results for the climatic extremes of Lake O1arles, louisiana(cooling-dominated), and Madison, Wisconsin (heating-dominated), andthen discussed in detail & We also briefly describe studies in progressto measure peak load impacts of fenestration ng an outdoor testfacility and occupied ldings~

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PEAK DEivlAND SAVINGS FROM OAYLIGHTING IN COt4r"1ERCIAL BUILDINGS

s~ Selkowitz, D. Arasteh, and Re JohnsonEnergy Efficient Buildings Program

Lawrence Berkeley Laboratory

BACKGROUND AND INTRODUCTION

Utility systems must provide sufficient generating capacity to meetthe coincident peak electrical load from residential, commercial, andindustrial customers. For a variety of reasons, the marginal cost toutilities of adding new generating capacity has escalated rapidly duringthe past few years~ Utility rate structures for non-residential users"frequently include hi gh peak demand charges that refl ect the cost ofproviding new peak generating capacity [1,2]~ These high charges are anincentive for building owners to adopt design features that'minimize abuilding 8 s peak electrical demand.

Fenestration design in commercial buildings is a major determinantof total energy and peak electrical demand requirements for space condi­tioning. The impact of fenestration can be positive or negative depend­ing on both architectural design decisions and building operation. For­tunately, those solutions offering substantial energy benefits also fre­quently offer improved thermal and visual comfort~ Achieving thesebenefits requires an understanding of component energy impacts andinteractions and a sensitivity to architectural design issuese

We have studied peak electrical demand, energy consumption, thermalperformance, and lighting performance in detail using DOE-2.18, a build­ing energy simulation program, as the primary analysis tool, parametri­cally varying the important fenestration and electric lighting variablesfor 16 Ue S. cl imates$l DOE ....2 is used because there are few measuredperformance data of sufficient d ail on fenestrationls net thermal per­formance and there is even less information on daylighting effects 9

Statistical a lysis was used to establish functional correlations fromthe resul an extensive number of 00E-2 runs@ The analysis

here focuses on the relationship between fenestration parame-el demand with and without daylighting, and pro-

a 1 di scussi on one the 16 es stu-s Angel es @

begin to understand peak demand savings, we investigate electricreductions due to daylighting as well as thermal loads with and

ighting@ Daylighting effects from both vertical windows andsk ights are considered0 We developed two prototypical

buil modules, one with windows and one with skylights, for whichfenestration and lighting characteristics are parametrically variedaaImportant peak demand and energy use patterns in these modul es can becharacterized on a per-unit floor-area basis and applied to other build-ing configurations. So far, our work has focused on an office confi­guration; retail and apartment modules have also been designed and stu­died in a few climatese Initial results indicate that the primarydifferences between office and retail spaces are related to such factorsas internal loads and operati ng schedul es rather than fenestrati on,energy consumption trends are nonetheless different, and each occupancy

0-244

SELKOWITZ ET ALo

type requires a separate analysis~ This paper is a synopsis of papersthat describe this work in much more detail [3-6].

To study daylightingls effects on perimeter-zone vertical windows,we designed a representative five-zone commercial office module. Thismodule (Fig- 1) consists of four identical perimeter zones, each 15 ftdeep, surround i ng a square common core zone" The eei 1i ng and 'floor aremodeled as adiabatic surfaces (no net heat transfer). The overallenvelope thermal conductance val ue, Uo' is hel d constant in _order toisolate solar gain and daylighting effects$ Thus, when glazing area orU-value change, the wall U-value is adjusted to maintain a constantoverall envelope conductance 6 After basi c performance patterns wereestablished, we varied the overall conductance over a representativerange. Fenestration characteristics were varied by changing U-value,glazing area, visible transmittance/shading coefficient (with visibletransmittance general.ly equal to two-thirds of shading coefficient), andexterior shading. A simple window management system is assumed in whichoccupant requirements for thermal and visual comfort result in the useof drapes or shades for an~ hour in which transmitted direct solar radi­ation exceeds 20 Btu/hr ft , or any hour in which window luminance pro­duces a glare index greater than 20~ Glare index is a measure of visualdiscomfort induced by the luminance of the window as viewed by an occu­pante The interior shading device reduces solar heat gain by 40% andvisible transmittance by 65%. For modeling vertical windows, identicalfenestration consisting of continuous strip windows is used in the exte­ri or wall of each peri meter zone. To study zone-by-zone eff ts, aseparate, constant-vol ume, vari abl e-temperature syste·,n wi th an econom­izer is used jn each zonee Use of other systems, such as a multi-zonevariable air volume systefn, could change resul

the skylight module, the perimeter zones were eliminated andindividual sk ights were uniformly distributed over the core zone'sroof, as indic ed in Fi·ge 1@ Exterior walls and the floor were modeledas adiabatic surfaces, which l1mi envelope energy flows to· the roofand skylight systeme The skylights modeled are diffusing whiteskylights typical of those commercially available. No window managementwas modeled as it is typically not found with skylightse Fenestrationcharacteri s vari incl uded U-val ue, skyl ight area, 91 azi ngshading coefficient and sible transmittance, and light well loss fac-tor (the fraction of S1 e light transmitted by the glazing thatenters the space, i.e @ , that not absorbed or refl ected out by the1 i 1 wall s ) [7 ] @

module types, extensive sensitivity studies [8,9] were con­determine details of the final module designo Variables con­

dered and not found to significantly affect daylightingls impact onannual peak demand d energy use trends included ceiling height, module

ze, and office equipment load~ For most of our study, the minimummaintained illumination level was 50 footcandles (fe). T light­control reference point was placed at two-thirds of the perimeter zonedepth for the five-zone module, and at the diagonal intersection of thefour adjacent skylights in the center of the space.

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SELKOWITZ ET ALo

Based on a maintained design illuminance of 250 fc, electric lightingpower density was varied from 007 to 2.7 W/ft , resulting in lightingsystem uefficacies u of 71 to 19 lumens/watt, respectively9 We use effi­cacy to represent the ratio of useful workplane illuminance divided byinstalled lighting power density. We exarnined the effects of steppedswitching and continuous dimming in response to daylight~ The continu­ous dimming system dims from 100% light output with 100% power to 0%light output with 10% residual power.

The 00E-2.1B building energy simulation program, used as the model­ing tool, incorporates a dayl ight.ing model that calcul ates hourly inte­rior daylight illuminance for each zone of a building based on architec­tural design and hourly weather data [lO,ll]~ iV10re than 5000 uOE-2 runswere performed in this study. Extensive analysis was completed foreight climates ranging from cooling-dominated (Lak.e Qlarles~ Louisiana)to' heating-dominated ,(Madison, Wisconsin) 0 More 1imited analysis wascompleted for eight additional climates to provide sufficient data forclimate generalization@ Peak. plant-level electricity demands for each.module type were calculated by DOE-2 for each foodule configurationo

ANALYSIS OF RESULTS

The data from these numerous parametri c runs demonstrate the corn-exity of daylighting energy analysis relative to our primary

concerns--cl imate, or; entati on, and fenestrati on--al ong wi th other phy­s; cal and operati anal bui1di n9 parameters e For bui 1di ngs wi th vert; calwi ndows, us; ng a 5i ng1 e 1umped parameter [the product of the floor-to-

ling window-to all ratio (WWR) and the sible transmittance (VT)]define dayligh performance simplifies the analysis and yields

accurate results [12]@ We call this new lumped parameter the effectiveaperture (Aewl @

A milar lumped parameter skylights is constructed by includingthe vi ble 11 -well factor (WF) and SUbstituting skylight-to.... roofratio (SRR) WWR@ This product, SRR x VT x WF, is the effective aper....ture (Aes ) for skylights@ Because the relationship between siblelight transmitted through the skylight system and solar heat gain is not

1y , we uated several SC val ues for each val ue ofeffective aperture in daylighted cases& We define the ratio of the

vi e light transmitted by the skylight system to shading coefficientby Ke so that K = VT x WF/SCe This distinction is necessary since achange in the will factor will reduce the 1ight fl ux transmitted to the

but not change the solar gaino

In meet ASHRAE gO-type cri teri a, we requi re that the1 heat transfer coefficients are constant over the range of effec­

ve apertures studiede Thus, the relationship between increasing effec­ve aperture and peak demand requirements is primarily a function of

light- and heat-admitting properties of the fenestration systemo

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SELKOWITZ ET AL.

Lighting Energy Savi~gs

Before looking specifically at peak demand savings with daylighting,it is first instructive to analyze lighting energy savings with day­1ighting.. The dimming system considered is continuously responsive tovariations in daylight level and maximizes the benefit from low daylightlevels. The simple, one-step (on/off) systenl reduces electric' lightingpower only when daylight exceeds the design illuminance requirement, andthus provides all required lighting; at zero electric light output thereis zero power consumpti on ~ Wi th a two-step system, hal f the el ectriclighting power is turned off when available daylight provides at least50% of the required illuminance. Thus the step-switching system is mosteffective at hi gh i nteri or dayl ; ght 1evel s, where it outperforms thecontinuous dimming system (which we modeled as having low-level parasi­tic power requirements); step switching is least effective where lowdaylight levels provide only a fraction of desired il1uminanceo Hourlyaverage illuminance levels for a skylight effective aperture of OG01with a continuous dimming system are given in Table 1; the illuminancelevel setpoint is 50 fe@

The principal effect of daylighting is to reduce electric lightinguseo As effective aperture increases, electrical consumption for light­ing in all climates first drops off sharply and then levels off@ For agiven effective aperture, fractional savings depend on the designilluminance 1 and the lighting control strategy~ Figure 2 illus­trates the change in fractional lighting energy savings for the skylightmodule as a function of effective aperture for three design illuminancevalues with a continuous dimming system, and for one illuminance levelwith both a one-step and a two-step systemo With the continuous dimmingsystem, the savings for small aperture areas are not linear with respectto design illuminance level~ For larger apertures, especially at lowerdesign illuminance levels, the shape of the curves indicates that day­1ighting becomes satur ed and further savings are impossible. Notethat a mi mum effec ve aperture is required before any energy savingsaccrue the stepped systems@ Performance of the one-step system con­

y lags behind that of the two-step system, as expected@

lighting control strategy has several consequences.1 apertures at the same design illuminance level, e dimming

control always outperforms the stepped system because, for many hours,the available daylight is below the control setpoint, allowing partial

ngs with the dimming system but none with the switched control~ Asincreases, the di fference between the two is reduced @

ly the switched system outperforms the dimming system because ofmming systernls low-end operating characteristics~ This pattern

in 1 imates and orientations.

c Peak Savings ~ith Da.tlighting

Daylighting l s major effect is to reduce the amount of electriclighting required. This leads to cooling load reductions and heatingload increases. We consider here only the case of an HVAC system withan electrically driven centrifugal chiller and a gas-fired boiler$ Thissystem typically has summer electric peaking; thus daylighting's total

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SELKOWITZ ET AL.

effect on peak el ectrical demand wi 11 be a net reduct; on due to bothlighting and cooling energy savings. The conclusions of this study arethus limited to summer peaking conditions. Patterns for the windowmodule and the skylight module differ and are discussed separately~

Windows. Figure 3 shows that, in the five-zone office module,fenestration imposes substantial peak dernand penalties unless daylight­ing is used. Without daylighting, peaks occur during sunny, hot after­noons at a time when the electric lighting is also at a maximume Whendaylighting is used, peaks occur under similar conditions; however,electric lighting requirements are quickly reduced to their minimum atslnal1 effective apertures. This results in associated cooling savingsas long as the effecti ve aperture does not increase past the poi nt(0.10-0.15) where added fenestrati on pri mar; ly prov i des excess sol argains. The peak demand in a daylighted building in tViadison or LosAngeles with moderate-to-large effective apertures is 14-15% lower thanthe peak demand in a nondaylighted ~uilding with identical glazing whenthe electric lighting is 1~7 W/ft). Savings in Lake Charles are.slightly less than in Madison and Los Angeles. This can be attributedto the combination of high latent load and high ambient temperatures atthe ti me of the peak in Lake O1arl es. In all cases, dayl i ghti n9 canreduce the peak load to below that of an opaque wall, (WWR)*(T ) = 0.00For this building module, the perimeter-zone floor space is on~y 37% ofthe total 0 The fraction of total building peak demand saved will vary

th the perimeter/core ratio.

A plot of required chiller size as a function of effective apertureis shown in g~ ~il1er size increases continuously with effectiveaperture even in the daylighted cases. This pattern contrasts with thepeak load patterns, which show an intermediate value of effective aper­ture for the mi mum peak loads with daylighting~ With daylighting atsmall apertures, chiller size increases less rapidly than without day­lightinge Beyond an effective aperture of 0.15 the rate of increase isthe same for both cases$ These results emphasize the importance of con-

ling ar gain if daylighti is to be successfully utilized to~~~~~A demand.

as a func on i 1 ectric lightingden Los Angeles is shown in g& 5. Changes in installed

ighting power are assumed to represent hardware changes that increaseor decrease luminous efficacy0 In all cases the illuminance design cri­

on remains 50 fc. For the nondaylighted cases, including a building1ng no ndows, ationship between peak demand and electric

light; power density is linear and the plots for different values ofeffective aperture are linear. However, for daylighted cases, the rela-

on p between peak and lighting load is not linear. For the sUlall\Ie aperture, Oel2, the peak demand with dayl ighting is always

less than the peak with opaque wall for any choice of installed lightingpower. However, with the larger effective aperture, O~27, the peak withdaylighting is only less than th~ with an opaque wall at lighting powerdensities greater than 1.2 W/ft. Higher solar gains with

2the larger

effec ve aperture offset daylighting benefits up to 1~2 W/ft @

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SELKOWITZ ET AL.

Skylight Peaks. Without daylighting, as in the five-zone module,peak electrical demand in the skylight module typically occurs duringsunny summer afternoons when cooling and lighting loads are at theirmaximum. Thus, in the nondaylighted case, peak electrical demandincreases with effective aperture in all climates. This is seen in Fig.6, which assumes the following five ~onditions: (1) Ke = 1.0, (2)installed lighting power (Lw) = 107 W/ft , (3) design illuminance level= 50 fc, (4) continuous aimming lighting controls, and (5) ASHRAE­suggested overall roof U-values. These values fall in the middle of therange of parameters considered and are representative of current build­ing practice~ However, for a skylight module with daylighting, and withmoderate and high lighting power densities, electrical peaks generallyoccur during warm overcast afternoons, when daylighting provides minimallighting savings. At these times, cooling loads from equipment and peo­ple, solar gains introduced at earlier hours, and high ambient tempera­tures are at a maximum and combine with near-maximum lighting loads toproduce the annual peak"o Los Angel es is not as strongly infl uenced bysolar gains as are Madison and Lake Charleso This is seen in the com­paratively flatter slopes of the nondaylighted curves and the more gra­dual decrease in electrical peak as a function of effective aperturewith daylightingo Peak electrical demand savings are different for eachcity because of weather conditions at the me of the peak.

In the previous paragraph, we assume that Ke :: 1.0, which isequi val ent assumi ng that the product of vi s1 bl e transml ttance andwell factor is equal to shading coefficient. Glazing materials used intypical skylight systems usually have s1 e transmittance valuesbetween O~7*SC and 1@ SC@ Skylights without light wells, by defini-

on, have a WF of 1. However, well factors can decrease the amountof vi ble 11 t entering a space to a small fraction of its originalvalue, depending on light-well reflectance, well height, skylight1ength , and skyl i ght wi d 0 A skyl i ght system wi th a 3-ft by 3-ftskylight, a 1~5-f deep well, and a 70% well wall reflectance results ina WF of Del. Increasing the well depth to 3@5 ft lowers the WF to

mately O~5 [7]~ We assume that light losses in the well contri-to ar n in the condi oned space@ This is probably a

rnIP"!QeO~~\8 ,p&,,"'.e!l"W'll,iII"IlT""§I on ~ A ntenance factor to account for dirt accu-on on a ight would probably reduce VT and SC

y same amount, so it would not alter Keo Thus, undertypic conditions, with a practical choice of available glazing materi-als with regard visible transmittance, Ke will vary between a minimum

O~5 a maximum of l~Oo However, new spectrally selective glazingllI'If'II""ll. "lI s wi enhanced bl e transmittance are becoming avail abl eo

in this paper the case of skylight systems with a K of 105the possibl e performance of future dayl ight-oriente! gl azi ng

skylight applications~

the nondayl ighted cases, at a given effective aperture, netar gains increase as K decreases$ In Los Angeles, this leads to an

increase 1n the electricar peak (Fig. 7), as one might expect in anyclimate where the peak demand occurs during the cooling season~ Withdaylighting, at a given effective aperture, the amount of visible lightavailable to the space is the same for all Kee O1anging the Ke changesthe sol ar therlnal impact to the space@ At small effect; \Ie apertures,

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SELKOWITZ ET AL9

dayl i ghti ng has a 1arge effect and cool i ng has a small effecte Afterdayl i ghti ng saturates the space, the energy use or peak delnand curvesare dominated by solar gainse This is reflected in the similarity ofthe slopes of the dayl ighted and nondayl ighted curves with effectiveapertures greater than 0.02. For low Ke values, there is a distinctmi n1 mum el ectrical peak demand. If one increases Ke one can use 1argerskylight areas without significantly increasing energy use or peakdemand"

O1anging the electric lighting power density (Lw) significantlyaffects the electrical peak. For Los Angeles, where day1ightinglsimpact is greatest, Fig. 8

2compares the 2base case (1. 7 Wlft ) to the

limiting cases of 0.7 W/ft and 2@7 W/ft ~ As L increases, lighting'sproporti onate share of the coo1i ng peak and e~ ectri cal peak ri ses ,increasing potential savings from daylighting. Note that minimumelectrical peak is still achieved at the lowest Lw level 0

Daylighting in the skylight Inodule can significantly decrease.required chiller size, unlike the case of the five-zone perimeter modulewi th wi ndows (Fi g. 9) 0 Part of the di fference between the skyl i ghtmodul e and the fi ve-lone modul e can be attri buted to the fact thatskylights provide savings over 100% of the skylight module floor area,while windows in the five-zone module can influence only 37% of thefloor area. However, a more ilnportant factor is the manner in whichdaylight is distributed in each space~ The more uniform distribution ofdaylight in the sk.ylight model utilizes daylight with its intrinsicallyhigh luminous efficacy (90-130 lumens/watt) more advantageously than a

delighted rimeter zone with a highly non-uniform light distributionand thus grea y reduced effective efficacy~ As skylight effectiveapertures become large enough for saturation to occur (around O@02),solar gains then dominate lighting savings, which leads to a steady risein required chiller size@ This is seen in the nearly identical slopesof the ighted nondaylighted curves at large effective apertures~

that with continuous dimming the lighting designon ightly affec peak electrical demand, andeffec ve apertures e Th i s mi ght be expected nee

cases with nuous mming controls occur duriow daylight 1 lity$

systems have an interesting effect on daylightingsay ngs ( 9 @ 10) $ As compared to the base case wi th

mIning, stepped systems provide considerably less peaksavings~ With stepped systems (in the case of Los Angeles),

do not necessarily occur during overcast periods as with the con-nuous mming systems@ Depending on effective aperture and the number

ectrical peaks with step systems can occur over a range ofons@ The greater the number of steps and the 1arger the effec­

ve aperture, the more the peak behavior resembles that of a continuousmming system0 For the one-step (on/off) system, daylighting does not

produce any peak savings for effective apertures smaller than Oq&Q050For the two-step system, daylighting savings first occur at an effectiveaperture of 0.0025$

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SELKO'W I TZ ET AI. ~

SUlvlMARY AND CONCLUSIONS

Fenestrati on is a potenti ally i ;nportant desi gn and conservati onstrategy in nonresidential buildingso The importance of daylighting asa load managelnent opti on is intimately rel ated to the i nterpl ay of day­lighting and solar control impacts~ To maximize economic benefits, theilnpact of dayl ighting on peak electrical demand as well as on energymust be better understood. Resul ts froID an hour-by-hour simul ationmodel that accounts for dayl i ghti '1g impacts hel p refi ne our understand­i ng of thi s campl ex subject. An extensive set of parametric analysesfor a simple office module in several cli,nates suggests the followinggeneralizations:

1~ The concept of an effective aperture greatly mplifies theparametric analysis. and eval uation of dayl ighting and fenestrationsystems with a minimal loss of accuracYe

20 Increas i ng fenestrati on area and/or transuli ttance increase day-lighting savings frequently reaches a point, pending on climateand, for windows, orientation, beyond which peak electrical detnandincreases due to greater cooling loadse

if daylighting strategies are to pro-3~ Control solar gain isvide peak sav1ngse

ighting may always be a ucooler u light source than fluores-cent lighti the conditions under which this statement holds truedepend on 15 window management installed lightingpower 0

5@ effective luminous cacy daylight will normally be higherin a pr rly designed, skylighted building than in comparables1 ighted meter LoneSe This conclusion could change ifimproved cal of daylight distribution are

6 ~ 1 lower peak e1ectri eil1 demand,re 1a er cool ing systems ttian· nonCiayl ightedDuil dings

er windows or skylights@

7~ 1i power and lighting control system charac-cs are or factors in deternlining the real val ue of day-

strategies~

8@ the above conclusions are sensitive to clisnate, orientation,other b lding modeling assumptions@

While we believe that these results represent the most comprehensiveperspec ve to date on this subject, we remind the reader that there are

11 few measured building data to verify simulation results. O1angesin base-case condi ons and operating assumptions Inay al so modify someconclusions~

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S£LKO~JITZ tT Al<t

Addi ti anal study is needed to better understand performance resul tsand to extend these results to a broader range of fenestration designs~

Studies of roof monitors suggest that fenestration designs that are moresophisticated than simple horizontal skyl ights should further improvefenestrati on perforlnance [13]. Further development of the 00E-2 modelto allow analysis of other architectural solutions (e.g., light shelves,atria) is in progress, as described in Ref. [14]GI We believe that theregression techniques we used [8] to simpl ify the representation of a1arge data set could al so be used to convert our data set to a simpleyet powerful design tool [15]. We are also working on experimental pro­jects to obtain the quantitative data required to build confidence inthe algorithms used in the simulation models [16], and have begun tocollect detailed performance data in innovative daylighted buildingse

ACKNOWLEOGEl\1ENT

This paper summarizes results of a number of studies (see refer­ences) on the energy and peak load impacts of fenestration in non­residential buildings9 Our colleagues R0 Sullivan, 5. O1oi, C6 Conner,·and S. Nozaki made essential contributions to those studies~

Thi s work. was supported by the Ass; stant Secretary for Conservati onand Renewable Energy, Office of Building Energy Research and Develop­ment, Buildings Systems Division of the U.S. Department of Energy underContract No. DE-AC03-76SF00098* Portions of this work were supported byBattelle Pacific Northwest laboratory, Richland, Washington~

REFERENCES

10 Sel kowi , S~, Johnson, R$, Sul1 ivan, R~, and 010;, S., uTheImpact of Fenestrati on on Energy Use and Peak Loads in Dayl ightedCommerci al Bu 11 di ngs, IS presented at 1983 Pass i ve Sol ar Conference,Glorieta NM, September 1983, Lawrence Berkeley Laboratory Report,LB 5889$ Lawrence Berkeley Laboratory, Berkeley CA 94720.

2~ Ac , J. Peak Load P cing: EuropeanBallingerPiibffihing CD., Cam6ridge

3~ Selkowitz, S~, liThe Impact of Dayl ight-Loads, II presented at the 1983 Internati anal

09 Gonference, Phoenix AZ, February 16-18, 1983, and to bein Energy and Buildings@ Lawrence Berkeley Laboratory

5620~ Lawrence-'flerkeley laboratory, Berkeley CA 94720~

4@ , R@, Selkowitz, $., and Sullivan, R., uHow Fenestration canc y Affect Energy Use in Commercial Buildings,1m presented

the 1 Energy Technology Conference, Washi ngtol1, D0 C., March19-21, 19849 Lawrence Berkel ey Laboratory Report LB 7330@Lawrence Berkeley laboratory, Berkeley, CA 94720@

5~ Selk.owitz, S., 0101, U@, Johnson, Ro, and Sullivan, R0, liThe Irnpactof Fenestrati on on Energy Use and Peak Loads In Oayl i ghted Commer­cial Buildings,U in Pro9!:ess ~'! P_a__s_~ive Sola!:. ~_n_e~r:gy ~s~e_~s_, 19_83@

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SELKO\JITZ ET AL~

Arnerican Sector of the International Solar Energy Society, BoulderCO.

69 Arasteh, 0&, Johnson, R&, Sullivan, R., and Selkowitz, S. EnergyPerformance and Savings Potentials with Skylights--DRAFT. LawrenceBerkeley Laboratory Report, LBl-17457 ~ Lawrence Berkel ey Labora­tory, Berkel ey CA 94720.

7. Illuminating Engineering Society of North Amer;ca* IES LightingHandbook: 1981 Reference Volume@ New York, pp 9-85 - 9-860

80 Johnson, R., Sullivan, R., Selkowitz, So, Nozaki, So, Conner, Co andArasteh, D., IIBuilding Envelope Thermal and Daylighting Analysis inSupport of Reconrnendations to Upgrade ASHRAE/IES Standard 90, II sub­mitted to Pacific Northwest Laboratory, 1983@ Lawrence BerkeleyLaboratory Report, LBL-16770& Lawrence Berkeley laboratory, Berke­ley CA 94720@

9& Arasteh, Do, Johnson, R., and Selkowitz, S$ The Effects of SkylightParameters an Daylighting Energy Savings - DRAFT~ Lawrence BerkeleyLaboratory Report, LBl-174560 Lawrence Berkeley Laboratory, Berke­ley CI\ 94720@

10@ Building Energy Simulation Group, lawrence Berkeley Laboratory,DOE-2 Supplement, Version 2~lB, Lawrence Berkeley laboratory Report,IBL-"B7uo;-[~3 Suppl @ ··(January 1983) @ Lawrence Berkel ey Labora­tory, Berkeley CA 97420~

11~ Selkowitz, S@ Kim, J~ J@ Navvab, M@, and Winkelmann, F6, "The DOE-2and SUPERlI Dayl i ghti ng Programs, Ii Proceed; ngs of the SeventhNational ve Solar Gonference, pp~ 417-422 19820 LawrenceBerkel Laboratory Report, LBL-14569@

~ Johnson, R0, Sullivan, R~, Selkowitz, S@ Nozaki, S@, and Conner, CePerformance and Desi gn Opti mi zati on wi th Dayl ight­

1983 International Dayl ighting Conference,16-18, 1983, and to be publ ished in

Berkeley Report, lB

Me, Conner, Ce, Kammerud, R~ Co, An dersson ,, W~, Howard, T$C~, Mertol, Ae, and Webster,

in Office Bu;l ngs,U Proceedings of the 1983yl ighting Conference, pp$ 355 ....3580 American Insti­

Architects, Washington, D0C~, January 1983.

140 kowi, S~, and Wink.elmann, Fe, uNew Models for Analyzing theThermal and Daylighting Performance of Fenestration," in theProceedi ngs of the ASHRAE/DOE Conference on Thermal Performance ofExterior Envelopes of Buildings, Las Vegas NV, December 6-9, 1982$Lawrence Berkeley Laboratory Report, LBL-14517@

SELKOWITZ ET AL.

15@ Sullivan Re, and Nozaki, S~, nrJlultiple Regression Techniques Appliedto Fenestrati on Effects on Commerci al Buil di ng Energy Perfor.nance ~ II

submi tted to the ASHRAE Semi Annual f4eeti ng, Atl anta GA, January1983. Lawrence Berkeley Laboratory Report, LBL 16645.

160 Klems, Je, Selkowitz, S~, and Horowitz, S~, leA Mobile Facility forMeasuri ng the Net Energy PerfOrrl1dnCe of ~~'i fldows and Skyl i ghts, II

Proceedings of the Third International Symposium on Energy COnserva­tion in the Built Environl11ent, Dublin, Ireland, 1981~ LawrenceBerkeley Laboratory Report, LBl-12765o

Table 10 Skylight module: average illuminance (footcandles) at daylighting referencepoint 0

Los Angeles: WWRxVTM=0001; WWR=Oe05; SC=VT=002; UO=O~090

rHJUR OF tJ~y

1 lth.. l

tt ~ () 7 ts q 1. 0 11 ll. L .3 1 It 1 5 ). b A. 7 1 ij 19 lO 2. 1 22 1. j ZAt 11 au k $

o J tJ I) \) v 0 24 38 52 66 72 78 68 56 42 20 8 J 0 0 0 C) ~

o 0 0 0 \) \) 0 0 14 28 38 44 44 38 28 14 4 0

o :> \} 0 tJ .J 0 0 20 36 52 56 58 52 42 24 10 0

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o J 0 0 0 \J ~ 14 26 40 52 58 56 48 34 18 6

o 0 u I,) 0 J 0 u 22 36 46 50 48 40 26 12 2

o J iJ 0 U U 0 28 42 58 68 78 80 74 64 46 26

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JAN

AUG

DEC

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D....254

S:LKOJ:1IT7 ET AL ~

Plan

+ + + + I+ + + + I

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~_~L~-~~+-----~_R\ ISkylight ILocations I Core zane

(in sky- Ilighted

100 ft

~12 ft

100 f t. ----p"'I

Window width variel 15 f twith parametric

Figure l~ Building module description~

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Figure 2~ Lighting energy requirements wittdaylighting for skylight modulein Los Angeles; comparison of D-255lighting level and contro1~

Figure 3§ Peak electrical demand for windowmodule; continuous dimming vs nodaylighting controls 0

SELKOWITZ ET ALs

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...................

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UGHTING PO'WO 00\tSffY - W/sf

Figure 4~ Chiller size as a function ofeffective aperture for officemodule with windows; continu­ous dimming vs no daylightingcontrols"

Figure 5~ Peak electrical demand as afunction of lighting power den­sity: Los Angeles, officemodule with windows; contin­ous dimming vs no· daylightingcontrols ..

6~ .

)( K8Bt.O NO

C 1iCiRU NO

IIIJI~::~

B ~!-9_:-.~

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0.01 0.02 0.03D'fECTIV[ APERTlJR[

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u

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Peak electrical demand forskylight modules~ Shows con­tinuous dimming vs no day-lighting controls 0 D-256

Figure 7~ Peak electrical demand forskylight module in Los Angeles,Shows K variation with andwithoute daylighting@

SElK01~ITZ ET ALI

..

......................................... e e. __ -M

0.01 0.. 0..03D'm:fM: APER1'URE

II"I1-~

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D 1.1 wa!'t!I!f -nd

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A NO DAYUGH1'ING

)(~..~!Q

O-t---~--.....---ll""""""'-""'--a0..00

Figure 8~ Peak electrical demand for sky~

light module in Los Angeles&Shows continuous dimming vs nodaylighting controls~

Figure 9~ Chiller size as a function ofeffective aperture for skylightmodule in Los Angeles~ Showscontinuous dimming vs no day­lighting controls~

~tO ~t1W/Sr ASHRA[ Uo VAU.JESGG

t40,.~~~- .... -

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K ~: 1S'IJ!.. _D5fR;_~~ ..III 7Of'C; ctl __m~t-;~ .M ~!.Cl..~ _

0.01 0.02 0.03 CUMEn"EC11VE APERTURE

Figure lO~ Peak electrical demand as afunction of lighting load andcontrol type for skylightmodule in Los AngelesG

0-257