DDEELLTTAAPortfolioDemonstration and Evaluation of Lighting Technologies and Applications • Lighting Research Center

Lighting Case Studies ▲ Volume 2, Issue 2

Sacramento Municipal Utility DistrictCustomer Service Center

Sacramento, California

Type:Office Building

Site Sponsors:Ledalite Architectural Products, Inc.Advance Transformer Co.Lighting Research Center

The new Customer Service Center (CSC) atthe Sacramento Municipal Utility District(SMUD) consolidates all customer-relatedactivities into one building near its administra-tive headquarters in Sacramento, California.The CSC is a 184,000 square foot (17,100square meter) facility. Its four wings, linked bya central lobby hub, were specificallydesigned to use the abundant California sun-shine as a light source.

Each wing is a 70-foot deep (21 meter) rectan-gle running east to west. The southwest andsoutheast wings are smaller and lower thanthe four-story northwest and northeast wings,allowing direct sunlight to strike all south-fac-ing walls. North-facing walls have large win-

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Project Profile

Customer Service Center of the Sacramento Municipal Utility District, Sacramento, California

dows, while south-facing walls have smallwindows with exterior and interior lightshelves to limit glare and bounce light deeperinto the office space. All windows have verti-cal blinds so that employees can manuallycontrol window glare. Additional deep-wellskylights on the top floors of each wing pro-vide diffuse daylighting for office workers onthese floors.

Most CSC employees have open-office work-stations, where they use computers and per-form a variety of paper tasks. Direct/indirectlinear fluorescent luminaires, dimmed byphotosensor feedback during the day, main-tain a low level of ambient lighting. Employ-ees use adjustable compact fluorescent task

lights to boost light levels at their desks asneeded. A programmable energy managementsystem (EMS) can switch ambient office light-ing to accommodate flexible work schedulesand after-hours maintenance crews.

A grove of native redwood trees is surroundedby a dramatic three-story glass-wall lobby; thetrees filter the sunlight and serve as a focalpoint. At dusk, uplights in the lobby switch onto highlight the architectural design.

DELTA also studied small copy rooms withmanual on/auto off occupancy sensors andsunny employee break rooms with verticalblinds, which offer a change of atmospherefrom the offices.

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Portfolio Lighting Case Studies

● Lighting Objectives

● Use energy-efficient lighting products to reduce the lighting power density to well below that allowed by the California

energy code.

● Demonstrate the energy-saving potential of controlled daylighting in office spaces.

● Provide low-glare ambient lighting for computer users.

● Provide flexible, individually controlled task lighting at employees’ workstations to increase task illuminance when desired.

● Demonstrate the benefits of quality lighting design in an office space using commercially available technology.

▲ Lighting and Control Features

▲ Direct/indirect lighting. Suspended linear fluorescent luminaires distribute light evenly across the ceiling while directly

lighting work surfaces.

▲ Energy efficiency. Primary light sources are T8 fluorescent lamps powered by electronic dimming ballasts. Luminaire-

mounted photosensors signal ballasts to dim electric lighting continuously in response to the available daylight.

▲ Architectural daylighting. Large windows, light shelves, and skylights admit controlled daylight into the open offices, while

operable blinds and louvers provide additional glare control when needed.

▲ Low-power, adjustable task lights. Employees can move their adjustable-arm task lights to supplement ambient light levels

in their workstations.

▲ Occupancy sensors. Lights in copy rooms and private offices are automatically switched off after occupants leave the room.

TechniquesProject SpecificationsThe principal light source for the CSC is theF32T8 4’ (1220 mm) rapid-start (RS) lamp with acolor rendering index (CRI) of 75 and a correlat-ed color temperature (CCT) of 3000 K (warm).These lamps are used in suspended up/down-lights, wall-mounted uplights, architectural slotsrecessed in light shelves, and recessed troffers.

CFT9W compact fluorescent lamps (CFLs) witha CRI of 82 and CCT of 2700 K are used in tasklights and downlights. Lobby uplights use coat-ed 400-W metal halide (MH) lamps, 3700 Kand 70 CRI.

Ballasts for T8 lamps are two- and three-lampRS electronic dimming ballasts, capable of con-

tinuous dimming down to 20% of maximumlight output. (Newer versions of this ballast arecapable of dimming down to 5% output.) Mostof the CFL lamps are powered by high powerfactor (HPF) magnetic ballasts, although theadjustable task lights use two-lamp HPF elec-tronic ballasts. HPF magnetic ballasts power theMH lamps.

distribution. Oval extruded aluminumhousing, 3.5” x 9” (89 x 230 mm).Lamp: F32T8/RE730

C Architectural light slot recessed in lightshelf for accent lighting of vertical blindsbelow. Slot equipped with 6’ (1.8 m) fluorescent striplight, one lamp in crosssection, and 1” x 1” x 1” (25 x 25 x 25 mm) cell louver. Louver finish ismatte gray. Lamps: (2) F25T8/RE730

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NORTH

A Pendant-mounted fluorescent direct/indi-rect luminaire (70% up/30% down), onelamp in cross section, with 2.25” high(57 mm) specular parabolic louversspaced 3” (76 mm) apart in downlightaperture. Oval extruded aluminum hous-ing, 3” x 10.5” (76 x 270 mm), in con-tinuous rows. Lamp: F32T8/RE730

B Wall-mounted fluorescent uplight, onelamp in cross section, with asymmetric

Lighting plan, third floor, northeast wing

Lighting plan, fourth floor, northeast wing

Key Plan

Key Plan

D Recessed CFL downlight, 8” (200 mm) diameter aperture with3” (76 mm) high, clear specularparabolic cross baffles. Lamps: (2) CFT9W/RE827

E Recessed CFL downlight, 8” (200 mm) diameter open aperture with black multigroovebaffle. Lamps: (2) CFT9W/RE827

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Portfolio Lighting Case Studies

J Task light mounted to worksta-tion partition. Rotatable head 8” wide x 10” long x 1-1/2”high (200 x 250 x 38 mm),attached to a hinged arm. Aspecular silver plastic louverwith cells 5/8” x 5/8” x 3/8” (16 x 16 x 10 mm) blocks light above a 45° viewingangle. Lamps: (2) CFT9W/RE827

Lighting plan, lobby

Key Plan

WattageInput wattages for luminaires includeballast watts and are estimated frommanufacturers’ published literature. Allcalculations were based on the followingvalues:

T8 fluorescent lamps (electronicdimming ballast at full output)

F32T8 (4’): 30 W per lamp for 2- or 3-lamp RS ballastF25T8 (3’): 23 W per lamp for 2-lampRS ballast

Compact fluorescent lamps (electronicballast)

CFT9W: 18.5 W per 2-lamp HPFballast

Compact fluorescent lamps (magneticballast)

CFT13W: 34 W per 2-lamp HPF ballastCFT9W: 13 W per 1-lamp HPF ballast

Metal halide lampsMH400W: 458 W per 1-lamp HPFballast

F Recessed 1’ x 4’ (0.3 x 1.2 m) luminairewith 9-cell, 3” (76 mm) deep semi-specular parabolic louver. One lamp per luminaire, but lamps tandem-wiredto adjacent luminaires to avoid use ofone-lamp ballasts. Lamp: F32T8/RE730

G Wall-mounted MH uplight located 27’(7.9 m) above floor to light the ceiling ofthe main lobby. Yoke mounting providesaiming adjustment of the cylindrical

extruded aluminum housing. 10” high x16” wide x 24” projection (250 mm x410 mm x 610 mm). Integral ballast. Lamp: MH400/C/U

H Track-mounted CFL floodlight located in third-story window niches to uplightthe perimeter of the lobby ceiling. Ovalcast aluminum housing, 4” x 6” x 12”(100 x 150 x 300 mm). Lamps: (2) CFT13W/RE827

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DetailsThird floor open officeThe open offices on this floorof the CSC’s northeast wingare representative of most ofthe offices in the building.Employees work flexiblehours, but most are at theirdesks from 8:00 a.m. to 4:00 p.m. They respond tocustomer calls and corre-spondence, spending a largepart of their day working atcomputers. During daylighthours, a combination of 3rd floor, north wall

Cross section of 3rd floor, day

Cross section of 3rd floor, night

3rd floor, south wall

11’-2”8’-10”

210 cd/m2

180 cd/m2

140 cd/m2

220 cd/m2

110 cd/m2

210 cd/m2

100 cd/m2

190 cd/m2

120 cd/m2

190 cd/m2

110 cd/m2

200 cd/m2

100 cd/m2

210 cd/m2

80 cd/m2

140 cd/m2

190 cd/m2

70 cd/m2

110 cd/m2

300 cd/m2

51 fc32 fc

29 fc

28 fc39 fc

39 fc

41 fc98 fc

0 2’ 4’ 8’ 16’

0 1m 2m 4m

8’-2”

3’

50 cd/m2

200 cd/m2

100 cd/m2

210 cd/m2

80 cd/m2

190 cd/m2

90 cd/m2

180 cd/m2

90 cd/m2

190 cd/m2

90 cd/m2

190 cd/m2

90 cd/m2

190 cd/m2

70 cd/m2

160 cd/m2

110 cd/m2

50 cd/m2

30 cd/m2

30 cd/m2

24 fc28 fc

25 fc

27 fc30 fc

36 fc

25 fc24 fc 8’-2”

3’

11’-2”8’-10”

controlled daylight and electric lighting provides28 to 98 footcandles (fc) (300 to 1100 lux [lx])on the workplane, depending on proximity towindows. (See cross section.) Rows of direct/indirect luminaires (type A) are suspended 28”(700 mm) overall from the ceiling, spaced 8’(2.4 m) on center. A photosensor mounted onthe bottom side of each row of luminaires sig-nals the electronic dimming ballasts to dim thelamps in response to the amount of light it sens-es. Within 15’ (6.1 m) of the windows, the sys-tem is set to maintain a minimum of 30 fc (320 lx) on the workplane. In the center of theoffice floor, there is little contribution from thedaylight, and the system has been set to deliverfull light output.

The ceiling luminances are very uniform, rang-ing from 70 to 220 cd/m2. This falls within themaximum 4:1 ratio recommended by the Illu-minating Engineering Society of North Ameri-ca’s Recommended Practice for Office Lighting(ANSI/IESNA RP-1-1993). Only the section ofceiling directly above the interior light shelf atthe south wall exceeds this luminance ratio.After sunset, the ceiling luminance patterns are

7

Portfolio Lighting Case Studies

even more uniform, not exceeding 3:1 maxi-mum to minimum.

Built into each window light shelf is a louveredfluorescent light slot (type C) that washes thevertical blinds with light so that the blinds arenot in silhouette against the bright window. Atnight, the lighted blinds provide vertical surfacebrightness, which helps the office look openand inviting to employees working late.Recessed CFL downlights (type E) perform thesame function, accenting the columns betweenwindows. After dark the electric lighting aloneprovides 24 to 30 fc (260 to 330 lx) on theworkplane.

The architectural daylighting fea-tures windows, light shelves, andskylights. All windows are double-glazed for thermal insulation.South- and east-facing windowsare divided by an exterior lightshelf. The windows above the shelfare clear; the lower windows arelow-e (“low-emissivity”) glass, tint-ed for 30% light transmission. Thelight shelves extend inside the glassand are painted white to maximizethe reflection of low-angle sunlightonto the ceiling. A suspendedtranslucent “sail” of woven whiteplastic extends the light shelf fur-ther into the office. It diffuses andredirects sunlight onto the ceiling,providing a pleasant glow whileblocking upper window glare.

The light-colored, perforated verti-cal blinds block 95% of the day-light, allowing employees to elimi-nate glare while retaining the view.

North-facing windows in this areaare larger than south-facing win-dows and are also fitted withblinds, but they have no lightshelves or sails. DELTA observedthat the blinds are rarely drawn onthe north side because direct sun-

Section through light shelf and sail

light seldom reaches this face of the building.As a result, daytime illuminances here are high-er, from 47 to 98 fc (500 to 1100 lx) with noblinds used. Nighttime illuminances at all window workstations are 24 to 29 fc (260 to310 lx).

Fourth floor open officeThe lighting system on the fourth floor differsfrom lighting on lower floors. Large 4’ x 6’ (1.2x 1.8 m) skylights with splayed light wells arespaced on a 24’ x 20’ (7.3 x 6.1 m) grid. Eachskylight distributes cheerful daylight to manyworkstations with no uncomfortable heat or

4th floor, day

4th floor, night

3’

8’-2”

1’-3”4’-7”2’-6”

6”

2’-6”

5’-10”

0 1m 2m

0 2’ 4’ 8’

3’

naires (type A) run north to south across thespace, perpendicular to the linear luminaires onlower floors. The light output of all of theseluminaires is controlled by photosensorsmounted on the bottom side of the luminaires,regardless of their proximity to windows.

Workstations and task lightingMost of the open office workstations have parti-tions that are 61” (1.5 m) high or less, but sev-eral offices have 81” (2.1 m) partitions. Unfortu-nately, taller partitions located next to windowsblock daylight and views for employees work-ing near the center of the floor. All workstationshave light- to medium-color finishes (between

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30% and 50% reflectance), andmost have an L-shaped work sur-face with a corner bookshelfabove the computer screen.Workstations were intentionallyconfigured without overhead binsin order to reduce shadows onwork surfaces.

Every workstation has a movable-arm task light mounted on a verti-cal joint in the panel. Employeescan reposition their task lightswithin their workstations, so tasklight use varies widely. Someemployees prefer the task lightabout 18” (460 mm) above thedesktop for an additional 70 fc(750 lx) of reading light. Othersextend the arm as high as 30”(760 mm) above the desktop,using it as an area light which putsan additional 30 fc (320 lx) on thedesktop. A few individuals believethey have insufficient ambientlight in their workstations and usetwo task lights at once; others do

Cross section of 4th floor, day

Cross section of 4th floor, night

glare. The translucent skylight material is a triplelayer of plastics with a prismatic layer sand-wiched between clear layers to diffuse directsunlight. Daytime desktop illuminances rangeas follows:

Directly under skylights:35 to 150 fc (370 to 1600 lx)

At the edge of skylight opening:27 to 57 fc (290 to 620 lx)

Between skylights:18 to 50 fc (180 to 540 lx).

The south-facing wall is constructed with lightshelves, but unlike the lower floors, these haveno internal sail. In order to accommodate thepattern of skylights, the direct/indirect lumi-

300 cd/m2

930 cd/m2

23,000 cd/m2

300 cd/m2

89 cd/m2

80 cd/m2

120 cd/m2

25,000 cd/m2

3,600 cd/m2

190 cd/m2

110 cd/m2

100 cd/m2

140 cd/m2

200 cd/m2

3,600 cd/m2

17,000cd/m2

120 cd/m2

99 cd/m2

350 cd/m2

11’-2”76 fc8’-10”47 fc130 fc

50 fc150fc62 fc

130fc

110 fc

0 2’ 4’ 8’ 16’

0 1m 2m 4m

100 cd/m2

35 cd/m2

20 cd/m2

100 cd/m2

210cd/m2

200 cd/m2

190 cd/m2

20 cd/m2

39 cd/m2

110 cd/m2

200 cd/m2

190 cd/m2

200 cd/m2

110 cd/m2

31 cd/m2

20cd/m2

200 cd/m2

83 cd/m2

30 cd/m2

11’-2”15 fc8’-10”30 fc30 fc

40 fc38fc31 fc

41fc

15 fc

Workstation with task light (type J)

Details

partially closed to block themorning sun. Downlights (typeE) provide supplemental lightingon overcast days or after dark.

Main LobbyThe lobby’s three-story windowwalls encircle an open atriumthat is home to a small grove ofindigenous redwoods. The glasswalls provide a view to thetrees, which in turn shade thelobby from intense sunlight. Atsundown, the segmented dry-

wall ceiling is uplight-ed with MH wallsconces (type G), andthe third-story windowniches are uplightedwith track-mountedCFL floodlights (typeH). Nighttime floorilluminances rangeonly from 6 to 7 fc (65 to 75 lx), but thespace appears brightand visually appealingbecause wall and ceiling surfaces arelighted.

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Portfolio Lighting Case Studies

not even turn on their task lights. (See ProjectEvaluation on p. 10 for more detail on em-ployee reaction to task lights.)

Employee break roomsIn these areas, direct sunlight is allowed to pourin freely. With light finishes and full-height win-dows, the break rooms are bright, cheerfulplaces for employees to retreat from the officeroutine and take a visual break from their officeinteriors. Short sections of direct/indirect lumi-naires (type A) are suspended near the curvednorth wall, where the vertical blinds are usuallyopen. Blinds on the east window wall can be

Cross section through break room

Break room

Cross section of lobby

Lobby

30 cd/m2

32 cd/m2

66 cd/m2

85 cd/m2

110 cd/m2 130

cd/m2290 cd/m2 200

cd/m2

1600 cd/m2

640 cd/m2

8’74 fc37 fc28 fc51 cd/m2

0 1m 2m 4m

0 2’ 4’ 8’

21 cd/m2

21 cd/m2

32 cd/m2

77 cd/m2

80 cd/m2

63 cd/m2

170 cd/m2

10 cd/m2

41’

27’5

cd/m2

11 cd/m2

7 fc6 fc6 fc12

cd/m2

13 cd/m2

16 cd/m2

0 2’ 4’ 8’ 16’

0 1m 2m 4m

11’-2”

10

Design for daylighting By controllinghow much sunlight and heat enter the building,the architectural design of the CSC limits energyuse by reducing the maximum capacity of theheating, ventilation, and air conditioning(HVAC) systems needed for occupant comfort.Introducing daylight also reduces the demandfor electric lighting.

Dimming by daylight sensing Thelayout of the direct/indirect luminaires (type A)in the open office areas was designed to main-tain 30 fc (320 lx) on the workplane. Duringthe day, when daylight provides a substantialportion of that illuminance, photosensorsmounted on the bottom of the luminaires detectexcess light levels and signal the ballasts to dimthe electric lighting until the level is back to 30 fc (320 lx), or until the fluorescent lamps aredimmed to their lowest setting, 20% of theirmaximum light output. DELTA estimates thatdimming by daylight sensing at the CSC saves8% of the CSC’s connected load on averageduring core office hours.

Energy Management SystemSMUD employees are on flex-time work sched-ules, coming in as early as 6:00 a.m. and leav-ing as late as 7:00 p.m., but almost everyone isin the office between 8:00 a.m. and 4:00 p.m.The programmable EMS is capable of switchinglighting circuits via relay panels according towork schedules, maintenance crew shifts, andweekend or after-hours use. For most of thebuilding the EMS is currently programmed to

ProjectEvaluationEnergy ImpactDELTA used input watts from manufacturers’ lit-erature to calculate the lighting power density(LPD) for the entire CSC. The maximum LPD forall conditioned space in the building is 0.87W/ft2) (9.4 W/m2). However, the in-use powerdensity during the core office hours (8:00 a.m.to 4:00 p.m.) drops to 0.58 W/ft2 (6.2 W/m2).Most of the difference (0.18 W/ft2 [1.94 W/m2])reflects DELTA’s observation that during corehours the following conditions prevailed:

• Only about one-third of the task lights were on.

• Most of the automatically dimmable fluorescent luminaires were operating atreduced output.

• The lobby lighting was switched off by aphotosensor.

The table below summarizes the power densi-ties in the building compared to ASHRAE/IES90.1-1989 energy standards and the CaliforniaEnergy Commission Energy Efficiency Standards(Title 24).

ControlsLighting control in the CSC is primarily accom-plished with three methods: architectural designfor daylighting, photosensor-controlled electron-ic dimming ballasts, and an EMS. In addition,occupancy sensors are used in small rooms,and lumen maintenance strategies can beemployed for general lighting.

switch lights on at 3:30 a.m. and off at 10:00 p.m. on weekdays. After hours and onweekends the EMS makes periodic sweeps toturn lights off that may have been left on.Lights in the southeast wing switch on threeSaturdays a month for public access to meet-ing rooms. Open office areas have local over-ride switches for employees working late. Tasklights are not controlled by the EMS, butemployees are conscientious about turningthese off when they leave for the day.

Occupancy sensors Passive infrared(PIR) wall-switch occupan-cy sensors control lightingin individual offices andcopy rooms. Employeesmanually switch lights on,but the sensors will auto-matically switch lights off ifthey detect no occupantmovement for six minutes.

Lumen maintenance strategyDirect/indirect luminaires that are not nearwindows or skylights are still fitted with pho-tosensors. These sensors can monitor theambient brightness of the area below theluminaire, and can be set to dim the fluores-cent lamps if they detect conditions that cor-respond to more than 30 fc at the workstation.Since most lighting is designed to deliver 10to 25% more light than is needed initially, toaccount for light loss over life due to dirtaccumulation or lamp aging, these sensorscan automatically dim the lamps when thesystem is new. As lamps age and dirt accumu-lates, the photosensors signal ballasts to raisethe power delivered to lamps until maximumpower is reached. When luminaires arerelamped and cleaned, the photosensors sig-nal the ballasts to lower power once again.

Although the lighting in the CSC wasdesigned to use this lumen maintenance strat-egy, DELTA observed that photosensors forthese luminaires had been set for full lightoutput in response to employee requests formore light.

Building Areas and Lighting Power DensitiesSpace Total Area Total ASHRAE/IES* California Energy In-use LPD

(ft2) Connected LPD Allowed LPD Commission Energy during(prescriptive method) Efficiency Standards core hours

(complete building method)3rd flr— 18,700 0.89 — — —NE wing4th flr— 12,800 0.90 — — —NE wingRemainder 152,130 0.86 — — —of buildingTotal 183,630 0.87 1.57 1.5 0.581 W/ft2 = 10.76 W/m2

*American Society of Heating, Refrigeration and Air Conditioning Engineers/Illuminating Engineering Society

PIR sensor atcopy room

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Portfolio Lighting Case Studies

Environmental and Economic AnalysesThe CSC’s lighting design achieved significantenergy efficiency and reduced costs by usingenergy-efficient luminaires, lamps, and bal-lasts. DELTA compared the annual energy costbased on observed day and night use with ahypothetical model. This model was based ona Title 24 complete building LPD of 1.5 W/ft2(16.1 W/m2) with the following assumptions:

• 100% of open office lighting on 18 hours/day

• 100% of lobby lighting on 24 hours/day• 100% of mechanical room lighting on

four hours/day• 100% of public meeting space on for an

additional 12 hours/month• 10% of total lighting on 24 hours/day for

night lighting

Because SMUD is an electric utility, the CSC isnot charged for its energy use. However, themonthly electrical rate for a comparable com-mercially owned building would be$0.058/kWh plus a demand charge of$7.62/kW per month. The calculated annualenergy cost savings is $56,328; reduced light-ing load accounts for $43,073 and reductionsin HVAC use due to the lower lighting loadaccount for $13,255.

As a demonstration site for energy-efficientlighting, the CSC incorporates a variety oflighting and controls systems. The initial costof the electric lighting, including luminaires,lamps, controls, and installation, was $1.56million, or $8.50/ft2 ($91/m2), which is about50% higher than conventional office lighting,and provides a payback period of about 9–10years. The premium for photosensor dimmingis about $1/ft2, and is responsible for extend-ing the payback period by two years. This isbecause the energy savings due to dimming isa small percentage of an already very lowconnected lighting load. As the cost of thesetechnologies continues to drop, the paybacktimes will make them increasingly attractiveto building owners.

According to estimates of the United StatesEnvironmental Protection Agency (EPA),reduced energy use from this building (whencompared to a building at the Title 24 LPD of1.5 W/ft2 [16.1 W/m2]) will result in lowerannual power plant emissions of 524 fewer tons(475 metric tons) of CO2; 9,084 fewer pounds(4,055 kilograms) of SO2; and 3,916 fewerpounds (1,748 kilograms) of NOx compounds.Reducing these emissions into the atmospheremeans a smaller contribution to problems suchas global warming, acid rain, and smog.

Staff ResponseThe DELTA team surveyed 156 employees onthe third and fourth floors of the northeast wingof the CSC about their impressions and experi-ences with the lighting. They were asked aboutlighting in the open offices and their task lightsto find out which lighting features worked welland which, if any, could be improved. DELTAspecifically asked about visual comfort, task vis-ibility, window glare, appearance of the light-ing, maintenance, comparison to lighting inemployees’ previous offices, and any sugges-tions for changes. The employees DELTA inter-viewed were generally very satisfied with theappearance of the lighting in the open offices.Many had experienced glare problems in theirprevious offices and had noticed an improve-ment at their new workstations. Over 50%

believed the lighting is better than in similarwork spaces in other buildings.

Very few surveyed employees reported reflec-tion problems from electric lighting on comput-er screens. Some employees in workstationsnear windows mentioned problems with day-light and direct sunlight reflecting in theirscreens, which they learned to eliminate byadjusting the vertical blinds.

Employees responded positively to their tasklights; almost all the respondents agreed thatthe task light is useful for the reading and writ-ing tasks they perform. More employees on thethird floor use their task lights, and for morehours during the day, than on the fourth floor.This is probably due to the additional daylightavailable from the skylights on the fourth floor.All the employees agreed that the task lightdoes not cause glare, but fewer third-flooremployees think it is bright enough. Age doesnot seem to make a difference in task light use;the same percentage of under-40 workers usestheir task lights as over-40 workers.

LIGHTING SURVEY—Percentages of People Who Agree:3rd Floor 4th Floor Total Norm*

The lighting is comfortable 66% 96% 77% 69%The lighting is uncomfortably bright for tasks performed 2% 4% 3% 16%The lighting is uncomfortably dim for tasks performed 18% 4% 13% 14%The lighting is poorly distributed 16% 7% 13% 25%The lighting causes deep shadows 12% 0% 8% 15%Reflections from the light fixtures hinder work 2% 0% 1% 19%The light fixtures are too bright 0% 0% 0% 14%Skin has an unnatural tone under the lighting 0% 0% 0% 9%The lights flicker throughout the day 0% 0% 0% 4%

Compared to similar workplaces in other buildings, I think that:The lighting is worse 13% 7% 11% 19%The lighting is about the same 28% 46% 35% 60%The lighting is better 59% 46% 54% 22%Can read 6 point type or larger only 100% 100% 100% 94%Can read 4 point type or larger 79% 96% 86% 76%* Normative data for this survey based on over 1,200 responses from employees in several offices throughout the northeast United States.

“There is not enough light on my desk in theearly morning, but the task light fills in.”

“I really like my workstation. The skylight isgreat.” – Demand Side specialists

Copyright © 1997, Rensselaer Polytechnic Institute. All rights reserved. Neither the entire publication nor any of the information contained herein may be duplicated or excerpted in any way in any otherpublication, database, or other medium and may not be reproduced without express written permission of Rensselaer Polytechnic Institute. Making copies of all or part of this publication for any purpose

other than for undistributed personal use is a violation of United States copyright law.

ISSN 1075-3966 Printed on recycled paper

For publications ordering information contact:Lighting Research Center, Rensselaer Polytechnic Institute, Troy, New York 12180-3590 • FAX (518) 276-2999

Phone: (518) 276-8716 • e-mail: lrc@rpi.edu • World Wide Web: http://www.lrc.rpi.edu

Portfolio Lighting Case Studies

DELTA Portfolio Lighting Case StudiesVolume 2, Issue 2Sacramento Municipal Utility District

Customer Service Center,Sacramento, California

Site Sponsors:Ledalite Architectural Products Inc.Advance Transformer Co.Lighting Research Center, Lighting Transformations Program

November 1997

Program Director: Naomi MillerReviewers: Russell P. Leslie, Mark S. ReaProject Coordinator: Paula A. RodgersEvaluation Team: Naomi Miller, Kathryn

Conway, James UnderwoodTechnical Assistance: Sandra Vasconez,

Marylou Nickleson, Jeff Anderson, AndrewJohnson, Erika Gillmeister

Evaluation Team Leader: Peter BoycePublication Manager: Judith BlockEditor: Claudia Hunter

CREDITSLedalite Contacts: David Kriebel, Maarten

MulderAdvance Transformer Contact: Jeff IrmerLRC Lighting Transformations Program:

Kathryn Conway, Program DirectorSacramento Municipal Utility District Contacts:

Alan Suleiman, Program Manager, Energyand Technology Center; Rafael Fuentes,Senior Electrical Engineer, General ServicesDepartment; Tom McGhee, Control SystemsSpecialist, Electric System DesignDepartment

Architects: Williams + Paddon, Roseville, CAConsulting Engineers: Peters Engineering,

Sacramento, CAElectrical Contractor: Collins Electrical

Company, Inc., Sacramento, CA; Kevin Gini,Branch Manager

Luminaire Manufacturers: A, B—Ledalite; C,F—Columbia; D, E, H—Prescolite; G—Insight Lighting; J—Waldmann

Ballasts: A, B, C, F, G—Advance; D, E, H—Robertson; J—Waldmann

Occupancy Sensors: LightolierPhotosensors: PLC Multipoint, Inc.Energy Management System: GE Total Lighting

Controls

DELTA Portfolio Graphic Design andProduction: JSG Communications, Inc.

Photographer: Kenneth Rice

DELTA MEMBERSBonneville Power Administration

Consolidated Edison Company of New York, Inc.New York State Energy Research and

Development AuthorityNortheast Utilities SystemLighting Research Center

DELTA STEERING COMMITTEECraig Ciranny, Patricia Glasow, Roger Knott,

Mitchell Kohn, Peter Morante, Frank Napoli, Marsha Walton

The DELTA team made an hours-of-use study oftask light use during the day, discovering that thehighest use of task lights is between 10:00 a.m.and 3:00 p.m. During this time an average of37% of task lights were on when no one waspresent in the workstation, resulting in wastedenergy.

Maintenance and Product PerformanceSMUD has not experienced any significant light-ing maintenance problems or product failures.However, the factory engineer had to make twovisits to adjust the “set points” for the daylightphotosensors. The first visit was routine: theengineer set each photosensor to dim when itdetected the brightness equivalent of just over30 fc (320 lx) beneath it. However, this adjust-ment was made in an unfurnished space. Whenfurniture, partitions, and people moved in, thelighting conditions changed radically andemployees complained that light levels were toolow for comfort. The engineer promptly returnedto reset the set points. Employees now are gener-ally happy with the amount of light, but DELTAnoticed one area where employees had coveredthe photocells with bits of paper to fool the sys-tem into providing more electric lighting.

Several employees commented that the the lightsails, installed several months after the buildingwas occupied, reduced window glare problems.

Lessons Learned• Well-designed architectural daylighting mea-

sures can provide desirable contact with theoutdoors while controlling heat and glare.The coordinated combination of light shelves,sails, low-e glass windows, skylights andblinds at SMUD’s CSC effectively controlsdirect sunlight and glare.

• Daylight sensing controls can save energy.The combination of photosensors and elec-tronic dimming ballasts saved 8% of thebuilding’s connected lighting load between8:00 a.m. and 4:00 p.m. by dimming lampsnear windows and in skylight areas inresponse to daylight. Although the controlscost extended the payback period in thisinstallation, these controls could providegreater energy savings in buildings with high-er connected loads or higher energy rates.

• Employees appreciate task lights. Energy-effi-cient, movable task lights give employeesflexibility and control over the lighting condi-tions in their workspace without significantlyincreasing the lighting power density.

• Skylights can reduce the need for task light-ing. The deep, splayed light well design dis-tributes daylight without glare. The additional10 to 100 fc (110 to 1100 lx) on desktopsreduces the need for task lights.

• A daylight sensing system should be com-missioned with workstations in place. Open-office furniture can trap light and alter pat-terns of brightness. Photosensor settings oftenrequire readjustment when furniture is added,rearranged, or removed.

• Operable window blinds are important in adaylighted space. Employees near windowscan moderate excessive glare, heat, or illumi-nance by changing the angle of the blinds asthe sun tracks across the sky.

“I’m very happy with the lighting in here. I like it a lot. Daylight and views really make adifference.” – Demand Side specialist