Reflectors are specially shaped retrofittable metal sheets designed to improve the efficiency and light distribution of conventional white-painted, ceiling-mounted fluorescent downlight fixtures (Figure 1). With higher reflectivity and more directional control than the white paint on many existing fixtures, reflectors can significantly decrease the internal losses of fixtures and improve light distribution.
Figure 1: Reflector design
Well-designed reflectors improve fixture efficiency and can widen or narrow light distribution. This fixture also shows a small-cell paracube louver, which reduces glare but absorbs a lot of light.
Well-designed reflectors improve fixture efficiency enough to allow some delamping. Although manufacturers frequently claim that the use of reflectors will allow 50 percent delamping with little or no reduction in the fixture's light output, that goal is difficult to achieve. In fact, it is less a function of how good the reflector is than how bad the existing fixture is. In any application, delamping should be considered carefully, bearing in mind that it may also be possible to delamp without a reflector.
Nevertheless, because of the large population of existing 2 x 4 fixtures with four 4-foot lamps, removing two of these lamps is a common proposal. This can be a realistic goal if one or more of the following conditions are met:
- The space is measurably overlit, or a reduction in light level will not be noticeable.
- The existing fixture efficiency is extremely poor and cannot be corrected by cleaning or lens replacement.
- A proposed reflector will provide better light distribution, allowing more uniform illumination at a lower light level.
- Replacement of the lamp and ballast combination increases the average light output per lamp.
- A better lens, diffuser, or louver is also installed.
- Existing lamps were very close together, raising their average temperature while shading each other.