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New York Library cuts energy, boosts illumination



Energy consumption was cut by 34 percent and light levels boosted 30 percent in the main floor of The New York Public Library during a recent retrofit. Because the Mid-Manhattan library (branch), located on Fifth Avenue and 40th Street, is probably one of the busiest in the nation, appearance and lighting uniformity were just as important as energy savings.

The retrofit was initiated by the City of New York Office of Energy Conservation, working with the New York Power Authority (NYPA) as part of NYPA's nationally recognized High Efficiency Lighting Program (HELP). The library was included in the city's list of high priority applications targeted for lighting retrofits. The area involved was the main level of the lending library, which was previously lighted with recessed 400-watt mercury vapor downlights.

"Footcandle levels in the main floor of the library were low," said David Weiss, senior designer for Xenergy, Inc., the energy management services company that specified the lighting system. "The illumination was very spotty, and the shadows made it difficult to read the titles on the shelves. This is the main level of a heavily used library," he added.

"We wanted not only to reduce energy usage, but to upscale the space and add illumination. "
The lighting system chosen for the retrofit is Holophane PrismGlo® Apollo® luminaires with 250 watt metal halide lamps. The prismatic glass fixtures were chosen for their ability to control light and their decorative quality. Uplight from the fixtures is 40 percent.

"We were impressed with the fixtures' photometrics," Weiss said. "The glass refractors provide adequate levels of uplight and downward illumination without appearing too bright. "

Fifty-six PrismGlo luminaires replaced the 73 existing fixtures, with footcandle level of 40 maintained. Mounting height is 15 feet, and spacing is 12 ft. x 12 ft.

"This is an outstanding example of how our High Efficiency Lighting Program works," said New York Power Authority Chairman Richard M. Flynn. "We provide financial support and technical expertise, the two ingredients that public agencies most need to carry out a successful conservation effort. We're particularly pleased to have worked with a renowned and vital institution like the New York Public Library.''

According to Richard Hackman, senior economist, New York Power Authority, NYPA paid half of the cost of the retrofit, with the city paying the other 50 percent. NYPA guaranteed the city that the cost of the project would not exceed twice the annual savings in energy.

"Our interest in the project was twofold," Hackman said. "We wanted to save energy and fuel, and reduce peak demand." Holophane's Computer Aided Lighting Analysis (CALA) software was used to determine footcandle levels on both the floor and the ceiling prior to installation.

"The metal halide lighting source is much more efficient than the previous mercury downlights," said Richard Appelbaum, assistant director, New York City Office of Energy Conservation. "With the existing fixtures, much of the light was lost in the ceiling."

"Library personnel are very pleased with the new lighting system. It not only saves energy and dollars, but significantly brightens the space." Weiss commented, "The PrismGlo luminaires have a visual impact from the street because of the glass walls in the library. The metal halide fixtures have also improved the color rendition."

The New York Public Library is open 58 hours a week. The lighting system is controlled by a time clock.



 

 
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