and uses a source that costs approximately
one-fifth as much (figure 12.15).
When a more concentrated beam is
desired, PAR lamps are more efficient, deliv-
ering more light at a given wattage for the
same cost. PAR lamp downlights are used
for greater emphasis on the horizontal plane
than is usually produced by other downlights
(figure 12.13). This greater intensity of light
is called “punch.”
Almost all open-reflector downlights have
round apertures. Reflectors are available with
either an overlap flange or a flush ceiling
detail. The overlap flange is used in gypsum
board and acoustical tile ceilings to conceal
the uneven edge at the ceiling opening. Flush
details are used in plaster ceilings to create a
neat, finished appearance; the ceiling is plas-
tered directly to the edge of a plaster ring or
frame (figure 12.16).Reflectors.Specular aluminum reflectors
produce the most efficient beam control.
Semi-specular reflectors are slightly less effi-
cient, but they eliminate irregularities in the
lamp beam or reflected images of the fila-INTERIOR LIGHTING FOR DESIGNERS
Figure 12.14Parabolic, open-reflector R20 downlight with 3½-in aperture.