The ideal lighting for any visual activity is natural daylight. It is best for color rendition, and it has been shown to boost attitude and performance. Artificial lighting can only approximate the real thing, and then just a narrow band from the whole spectrum. It is always prudent to make the most of available daylighting since it is not only the healthiest but also the cheapest light source.
Few offices can get by on daylighting alone, however. A compromise is the use of multiple-level switching. The perimeter offices of a building with outside exposures can have some lamps in each fluorescent ceiling fixture on one switch and the balance on another.
With three-lamp fixtures, there are four possible levels of lighting (off, one, two, and three lamps on) that can be used to complement the available daylight. In large open offices, exterior hallways, or classrooms with perimeter daylighting, the outermost row of lights can be switched separately or turned on by a photocell when the ambient daylight is inadequate for the task. The small additional initial installation cost is compensated many times over by the savings and by the occupant’s greater comfort and productivity.
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Excerpted from Going Green, available as an eBook at this list of eBook retailers online.