Cleaning Fixtures Improves Illumination.

A study by the international Association of Lighting Management Companies (NALMCO) is expected to provide a road map for achieving potential savings of up to 10% of the lighting costs of many building owners everywhere for the life of the structure--all by simply cleaning fixtures. The Luminaire Dirt Depreciation study has taken scientific measurements of available light over the past three years throughout the test group sampling to determine the benefits--in terms of both improved lighting and reduced costs--of periodic cleaning of the lighting fixtures themselves, with a goal of installing fewer fixtures in office buildings, schools, health facilities, and retail stores.

"For the past half-century, the negative effect of light loss due to dirt accumulation on lamps and luminaire surfaces has resulted in reduced light levels," notes Norma Frank, past president of NALMCO and chairman of the Illuminating Engineering Society of North America's Lighting Maintenance Committee. "In addition, architects and lighting designers have been specifying and installing over-lighted initial design levels to compensate for accumulation of dirt, resulting in unnecessary up-front costs and more electrical power wasted daily," she indicates.

According to Robert Levin, a corporate scientist for Osram Sylvania, a previous study in the 1950s was conducted in the era before widespread air conditioning, during which many office and industrial tasks were different and produced types of dirt in the workplace other than what is often bund today. For example, office windows typically were opened from time to time and electronic machines were not in use, but early duplicators and lead pencils were commonplace. Moreover, different types of paints and building materials were in use, and lighting fixtures themselves have changed.

"All lighting systems lose light as they operate; fixtures get dirty; and lighting standards are provided to account for this. So initially you provide for more light, which means more expensive installation [and] more energy consumed, which also is more operating costs. If we have good, firm numbers on how much the light depreciates, the designer can cut back a bit on the amount he recommends initially."

Levin cautions, though, that once facility managers make these reductions, the lighting must be regularly maintained, making it viable to provide the minimal amount of excess light initially to allow for reasonable light loss due to dirt. After that, the fixtures can be periodically cleaned on a schedule.

A specially designed instrument--a Fluxometer--was utilized in gathering the lighting data throughout the three years of testing. This essentially is a light meter coupled with a handheld computer used for calculating and recording results.