needed. Two basic control strategies are
available: (1) control in space by electrically
positioning (switching) the lightwhereit is
needed and (2) control in time or supplying
lightingwhenit is needed.
Daylighting controlshave photosensors
that automatically adjust the electric lighting
to preset values. When daylight is available
and suitable (reaching task areas without
causing glare, for example), luminaires are
dimmed or turned off.
Lumen-maintenance controlscompen-
sate for the natural deterioration of the light-
ing system and the room surfaces over time.
They automatically increase the power to the
system so that the light output is kept at a
constant value.
It is advisable to use control systems for
daylighting, worker area individualization, and
window energy management. Individual con-
trols in office spaces go a long way toward
conserving energy and, equally important,
toward giving occupants a sense of control
over their immediate environment.INTERIOR LIGHTING FOR DESIGNERS