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Offices SSOE

Refractive Grid lens meets
lighting retrofit needs at SSOE

When the engineering and architectural firm of SSOE, Inc., installed a fluorescent lighting system at its Toledo, Ohio, headquarters during the , 980s, a minimal number of computers were used in designated areas. But, as the price of personal computers decreased and a unit appeared on nearly every desk, employees began complaining about eye strain, headaches and fatigue.

"We were having problems with glare on the monitor screens," said Steve Wheeler, senior electrical designer with SSOE.

"Because our employees perform so many different tasks, we needed a lighting system that would increase the comfort level on the screens while providing sufficient illumination on the horizontal work surfaces of the desks."

The original fixtures in the 7,500-square-foot open office space are 3-lamp 2' x 2' fluorescent units installed in a raised cove in the 5' x 5' modular lay-in ceiling. Once the decision was made to retrofit the system, a test was conducted with three replacement lenses: a 1/2" x 1/2" parabolic silver louver, a Holophane Refractive Grid lens with a white diffuse overlay, and a Holophane Refractive Grid lens with a clear overlay.

According to Wheeler, the objective of the test was to determine which lens would reduce glare and veiling reflections in three areas at the computer workstations: the monitor screens, the menu board and work surface, and the general area. Glare on the computer screens was created by fixtures located behind and around the workstations, while glare and veiling reflections on the menu board and work surface were produced by fixtures located directly overhead. The third area to be addressed was incidental glare or visual comfort perception (VCP) in the general space.

At the end of the test period, Wheeler concluded that the parabolic lens performed extremely well in its ability to reduce glare on the screen; the fixture nearly disappeared from the VDT. However, due to its cut-off properties, the lens performed the poorest of the three in regards to reduced glare on the menu board and adjacent workspace.

"In fact, the measurable amount of glare on the work surface actually increased by , 0 to , 5 percent," Wheeler said. "Although the VCP performance was very comfortable since the fixtures from a distance appear to be turned off, there were other considerations—such as the 'cave effect' resulting from too high of cut-off."

Since the ceiling system in the facility is a coffer design, Wheeler said he questioned whether total obstruction of the light source was desirable. Maintenance was also a concern. Due to the small cubes and finish, he felt the parabolic lens would attract dust, show fingerprints and be hard to clean, in general.

Wheeler indicated that the Holophane Refractive Grid lens with opaque overlay performed the best when all situations were considered. Although the glare on the VDT screen was not reduced to the same degree as with the parabolic lens, the difference was significant enough so as not to be offensive to the user. The Refractive Grid lens with white diffuse overlay, however, performed the best as far as reflection on the work surface was concerned.

"The white diffuse overlay seemed to smooth out the amount of direct glare and reflections," Wheeler said. "VCP performance was very good. Since the light source could still be seen, there was no "cave effect". Yet, incidental glare was cut enough so that employees did not feel any strain if they casually glanced up from a work station."

He added that maintenance is much easier with this lens since it can be wiped down with a damp cloth.
The third lens tested—the Refractive Grid lens with clear overlay—was not considered since it reduced glare only minimally.

Wheeler indicated that all three lenses reduced illumination levels by about , 0 percent, or , 2-, 5 footcandles. The parabolic silver louver produced slightly higher levels directly under the fixture, while the Refractive Grid lenses reduced the levels in a uniform manner.

During the test, the center lamp in the test fixtures was removed to help reduce eye strain and glare reflection and bring overall footcandles more in line with IES recommended levels for computer tasks. When the facility was retrofit, the center lamp was removed in every second fixture and the two outer lamps were removed and only the center lamp installed in the others.

"The comfort levels in areas where the fixtures were retrofit is greatly improved," Wheeler concluded. "There's a big difference when you walk into the area; you notice the contrast immediately."

To date, more than 300 Holophane Refractive Grid lenses with the white overlay have been purchased and installed, with the retrofit completed in the engineering and accounting areas. Wheeler said employees on other floors have expressed a desire to have their areas retrofit, too.

SSOE has installed the Refractive Grid lens for other jobs, such as dental offices and retail stores. Headquartered in Toledo, SSOE operates offices in Troy, Michigan; Bellevue, Washington; and Nashville, Tennessee. The firm employs about 700.


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