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Washoe County School District
 

Holophane luminaire reduce heat, and triple light level



A comfortable environment conducive to learning is essential if students are going to achieve. Excessively overheated classrooms and offices in six Northwestern Nevada elementary schools designecl and constructed in the early 1980's, plagues students, teachers, and administrative staff. Parents and teachers, the PTA of these schools, finally convinced the Washoe County School District to hire a consulting mechanical engineer with an international reputation in radiant energy processes and energy conservation to investigate the problem schools and recommend practical solutions. In 1989, the firm of Joe M. Beard & Associates, Inc. was retained by the school district.

An initial review of the history of these schools revealed that oppressive heating problems were noted when the schools were first occupied and had become more severe when a lighting modification was implemented several years after the schools were opened. The original lighting design, a 100% indirect lighting system utilizing four 400 watt metal halide ceiling pendant fixtures, failed initially to provide adequate illumination levels in the classroom seating area . This lighting defect was substantiated two years later by an independent electrical consulting engineering firm hired by the school district. The consultant's conclusion was that fluoreseent lights would solve the problem.

True to form, the second electrical engineer's recommendation was implemented when the School District retained yet a third electrical design engineer along with the original design architect to prepare lighting and ceiling modification plans. This team's design solution of adding white ceiling tile for greater ceiling reflectance and wall wash perimeter fluorescent lights was implemented.

The effects of the remodelling efforts were immediately noticeable. The classrooms became hotter faster when all lights were turned on; the average illumination levels in the student seating areas increased only slightly, and the perimeter walls were illuminated with down lighting.When Joe M. Beard & Associates began their field investigations, they traced the classroom and office overheating problems to the installed lighting systems.

The original HID metal halide light fixtures operated with a top surface temperature exceeding 350øF. Beard said the first action that his firm recommended was to install a lighting system that would operate at a much cooler surface temperature. The second step was to increase the interior illumination because surveys indicated that light levels in the seating areas ranged from 17 1/2 to 20 footcandles, which were well below required levels of 55 footcandles maintained.

The fixtures ultimately installed were PrismGlo luminaires from Holophane Company, Inc. Beard said the PrismGlos were initially considered when members of his firm learned about the units during an extensive literature search. Holophane was contacted and asked to provide sample fixtures for field testing.

Four-hundred watt, 250 watt, and combinations of metal halide wattage lamps in the PrismGlo fixtures were fiekl-tested in an existing classroom for three months, with input invited from teachers, students, and parents. During the test period, Beard also reviewed cornputer studies from Holophane's Computer Aided Lighting Analysis (CALA) software which predicted spatial lighting levels.

"When we installed the fixtures, we found the computer printout was slightly conservative, " Beard said. "We actually had better field measurements than what the computer had predicted."

With the Holophane luminaires, Beard said the school district was able to reduce the lighting power requirements in each classroom by almost 50 percent, while tripling the initial light levels. The energy savings resulting, with the six schools operating the luminaires about 10 hours per day, 200 days each year, were estimated at $30,000 per year based on a 44.56 kilowatt reduction and eight cents per KWH.

"The fact that we were saving energy was just the icing on the cake, "' Beard explained. "Our main objectives were still to lower the temperature in the classrooms and offices and improve the light level. "The PrismGlos reduced the maximum surface temperature of the operating fixtures 57 percent, from 350øF with the original units to 150øF with the new luminaires. The uniformity (or maximum value/minimum value) throughout the seating area improved dramatically from a measured 3.34 to a measured 1.60 after the PrismGlos were installed.

Initial PrismGlo light levels averaged 80+ footcandles in the seating area and were projected to decrease to 55 over a three year period. At the end of three years, according to Beard's recom
mendation, the district should conduct a group relamping at each school.

"Except for relamping, the Holophane fixtures are virtually maintenance free, " said Beard. "Estimated maintenance time for cleaning and relamping has been reduced by 90 percent compared to the original lighting fixtures. "

The PrismGlo fixtures selected provide 40 percent uplight and 60 percent downward illumination, which eliminated the problem of 100% indirect light. With the original fixtures, all of the illumination came out the very top of the fixtures, shined onto the ceiling, and was then diffused around the room by reflection, which resulted in an environment that was shadowless, very flat, and uninteresting. Beard said the Holophane fixtures supply enough indirect light to soften shadows while providing enough direct light to create a well illuminated, comfortable, attractive environment .

Each classroom has a vaulted ceiling and is designed with a total of four fixtures per roorn. Two PrismGlo luminaires are mounted in the high ceiling area using 400 watt metal halide lamps, and two in the lower ceiling area using 250 watt metal halide lamps. The fixtures were mounted in the existing fixture baseplates and sllspension brackets.

The conventional 75 watt double ballasts used with the previous fixtures were replaced with Holophane's high efficiency single ballasts that use about 58 watts (400 lamp). The ballasts are rernote, installed on the ceiling beam adjacent to the new luminaires.

Noise generation by the Holophane fixtures and ballast has been reduced by a factor of 10. The original double ballast operated in the range of 30 db, whereas the Holophane ballasts emit sound at 20 db or less.

Beard said that an added benefit of the Holophane fixtures was that the entire retrofit project came more than 30 percent under budget.

"The results are excellent, " he concluded. "When students look across the room, they can see the writing on the chalkboards. Now they can distinguish what's on a black and white flip chart, it's a remarkable difference. "

Comments from teachers have also been positive. One educator remarked, "The new lighting fixtures are cooler and brighter. They provide a much more cheerful and productive atmosphere. "

The six elementary schools retrofitted include Gomes, Palmer, Diedrichsen, Dunn, Dodson, and Lenz. These institutions are located in Reno, Sparks, and Sun Valley, Nevada.



 

 
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