Retrotec USACE - Manual (Page 220)

D90 ENERGY & PROCESS ASSESSMENT PROTOCOL
second occurs at night, when the janitorial crew turns on all the lights on the
fl oor, rather than proceeding zone by zone as it cleans. The solution is proper
controls and occupancy sensors. Figure D145 below (Sydney Australia, in the
middle of the night) contains examples of both effi ciency and waste. In the
foreground, we have a building that is mostly dark. In the background center,
a building has most of its lights on full. In the background to the left and right,
several buildings have controls that allow only parts of the fl oor to be lit.
Zoning of lighting controls is easily accomplished with occupancy sensors.
The sensors can be installed in the ceilings of open offi ce spaces, and the zones
can be defi ned by the area coverage of the sensors. Wall-mounted occupancy
sensors that replace regular light switches can control the private offi ces, and
occupancy sensors can control any other spaces in the building to provide in-
dividual room and zone control as well. Other types of control systems such as
time-based low-voltage lighting controls can be used, but they are generally
not as fl exible and are more costly to install.
D.5.4 Leaving Lights on in Unoccupied Spaces (Waste)
Figure D145. Buildings are lit with only a few
people working. Figure D144. Empty offi ce cubicle area with
the lights on full.
Electrical lighting is generally required by people in buildings to perform visual
tasks when not enough (or no) daylight is available. When we consider the need
for electric lighting in working environments, a basic principle is to make sure
that lights are turned off when people are not using the space. After all, if lights
are left on in a room and nobody is there, is the light really serving a purpose
(Figure D144)? Simple on/off controls such as on/off switches result in waste
because human intervention is required to turn the lights off when leaving the
area. Simple timed controls are a way to reduce waste due to lights being left on
at night or over the weekend. Occupancy sensors are a more sophisticated ap-
proach, sensing the presence of humans and turning lights off when no human
is occupying the space. In the offi ce buildings shown in Figure D145, every
hour of wasted electricity adds approximately a dollar to the electric bill.
A good way to test for the possible energy savings that could be achieved by
using occupancy sensors is to install some combination of occupancy-sensing/