Lighting. Page: 5 of 17
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Lighting Power Standards
The previous section mentions how new lighting level
recommendations encourage more energy-efficient
lighting systems. Many states have gone a step further
and adopted lighting power standards. These standards
establish a power limit for buildings and are given in
watts/ft2: that is, they set a maximum amount of power
that may be used to provide light in a building. This upper
limit on power use is called the lighting power budget.
The assumption behind lighting power standards is that
lighting practices and systems must be set up more
efficiently in order to have adequate light within the total
allowable wattage limit. These standards do not translate
directly into energy use (kWh) since hours of operation
vary, but they do give a good indication of energy use.
In many states the lighting power standards are being
applied just to new buildings, but in some states they
apply to both new and existing structures. These require-
ments appear in your state code. The Oregon standard,
for instance, limits overall lighting levels in offices to
2.5 W/ft' and in hotels and restaurants to 1.1-1.2 W/ft.
Remember, these are maximum standards. You should
be able to do much better in your building. The lighting in
many office retrofits falls well below 2 W/ft' and new
buildings are being designed with less than I W/ft' average.
In most rooms with fluorescent lighting, the new standards
can be approached by substituting high-efficiency tubes
and ballasts. Table 2 gives you an idea of the power
budget required to provide various levels of light with
standard fluorescents and an eight-foot ceiling. Energy-
eflicient tubes and ballasts can reduce the power budget
by 20 percent.
Footcandles Watts per ft=
Table 2: This table gives the power budget required fir
certain lighting levels with standard fluorescents. More
e ficient lights can reduce this budget.
Reducing Lighting Levels
After you have determined your building's lighting
requirements and the levels currently being used, you
can begin to plan lighting system modifications. There
are many ways to reduce excessively high lighting
levels while still providing adequate illumination.
Some of these methods are presented in the following
Delamping & Downwatting
In some areas, it is possible to cut back excessive light-
ing by removing bulbs. Some areas have more fixtures
than are really needed, so it is simple to remove some
bulbs from each fixture or to disconnect entire fixtures.
Fluorescent bulbs are wired in pairs to one ballast, so if
you wish to disconnect only one bulb, you will need to
install a "phantom tube" to keep the fixture working.
When removing pairs of fluorescent bulbs remember to
disconnect the ballast so it won't continue to use energy.
Sometimes it is possible to reduce lighting levels by using
lower wattage bulbs in place of higher wattage bulbs. For
instance, in some cases a 40-watt bulb may be substituted
for a 100-watt bulb and still provide adequate light.
Don't forget repainting as a part of your lighting conser-
vation scheme. Walls painted a light color provide more
useful light with lower wattage bulbs. White paint on
walls and ceilings can reflect light and can increase light
levels by as much as 100 percent.
Uniform lighting is rarely necessary. It is possible to de-
lamp in such a way that it reduces overall lighting while
providing higher levels of illumination at specific places
such as work areas or display areas. Selective lighting
works well in retail outlets where more intense lighting
on shelves and display racks attracts customer interest.
Task lighting places more light directly on a work area. It
is often used in offices since background levels can be
reduced to one-third the level required on desks or tables.
When rooms serve several purposes each having different
lighting needs, it is a good idea to install dimmer
switches. Dimmers allow the users to adjust the lighting
to the task at hand; when lights are turned down energy
consumption is reduced. Dimmers also permit adjust-
ment of lights according to the daylight available.
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Administration., United States. Bonneville Power. Lighting., report, September 1, 1992; Portland, Oregon. (https://digital.library.unt.edu/ark:/67531/metadc1317287/m1/5/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.