a large-area diffusing source. Coves are
useful to supplement more energy-effective
lighting methods, such as recessed down-
lighting systems.
The placement ratios in figure 12.38 are
intended to produce approximate visual uni-
formity. Specular reflections are minimized if
the ceiling surface is a high-reflectance
matte or satin finish. Typical cove dimen-
sions are shown in figure 12.39.
Custom-built coves are constructed of
wood, plastic, or metal. A glass or plastic
bottom is sometimes used to introduce a
downward component of light for sparkle.
Fluorescent lamps or cold-cathode
tubes are commonly used in coves because
they are energy-efficient, linear sources. All
lamps must be of the same color, and it is
best that they are of the same tube diameter
and have the same manufacturer to prevent
color variations on the lighted surfaces.
Lamps of similar light output per foot of
length are also desirable to avoid noticeable
variations in luminance on the illuminated
surfaces.
When the lamp mounting channels are
placed end-to-end, a noticeable gap in light
occurs because the lampholders take up
space and the lamps emit less light near
their ends. The shadows caused by this gap
may be avoided by staggering the mounting
channels so that they overlap by at least
three inches. Prefabricated single-lamp and
two-lamp staggered channels with overlap-LUMINAIRESFigure 12.37Column-mounted indirect luminaire.