Interior Lighting for Designers

function. Luminaires for these sources
require only a brightness-controlling ele-
ment; the most efficient is the open para-
bolic reflector. These luminaires are
relatively easy to maintain: very little dirt col-
lects on the underside of the lamp, and
every time the lamp is changed, the entire
optical system is replaced (figure 12.13).

R14 or R20 downlights are sometimes

used with spot lamps when a narrow beam

of light is desired from a small aperture

(figure 12.14), but PAR16 and PAR20

lamps are more efficient. R30 and R40

downlights are infrequently used; the wide

spread of the R flood lamp is available from

an A-lamp downlight, which is more efficient

LUMINAIRES

Figure 12.9Compact fluorescent, parabolic, open-reflector downlight with 6-inch aperture.