Guidebook for Energy Efficiency in Municipalities

Lighting overview
T3
Lighting accounts for about a third of all electricity used in municipal buildings, while
street lighting normally uses more energy than any other municipal activity. Lighting is
also important to a municipality because illumination affects:
the ability of staff and citizens to see accurately, affecting their ability to read, work
and move safely;
the appearance, ambience and functionality of a building and its fittings, affecting the
mood and morale.
When looking for ways to cut energy use, probably the first action most people think of is
switching off lights. This is of course very effective, but there are many other ways to
reduce lighting energy use, some of which are described here. Opportunities particularly
relevant to offices and street lighting are presented in the corresponding topics below.
Opportunities for savings
Use of daylight
Daylight is the most abundant and easily used form of free, renewable energy (solar
energy). A daylight sensor can control outside lighting and lighting in atria. Some sensors
have an adjustable light-level setting, making them suitable for areas which have access
to natural lighting but which require a higher lighting level than the setting of standard
sensors. Such areas could include glazed foyers, some depot buildings, indoor swimming
pool halls, undercover parking, or childcare centres.
In some cases, modest changes to a building will permit better use of natural lighting—for
example, skylights in a depot workshop or garage. Painting internal surfaces with light
colours and trimming vegetation back so windows have greater access to the sky can
improve the effectiveness of day lighting. Painting walls outside windows with light
colours to reflect more light into the room can also make a remarkable difference to the
amount of useful daylight.
Using daylight inside a building will improve the quality of the lighting in municipal
buildings by improving colour rendering, eliminating flicker and giving people a link to the
outside environment. However, too much daylight, especially direct sun, can create glare
problems and excessive heat. For example, a square metre of clear roof glazing in direct
sun delivers as much light as up to 40 standard 36-watt fluorescent lamps 1 . Good design
of day-lighting systems is critical.
Use the right amount of light
People need more light to read than they do to walk down a corridor, but offices and other
buildings are often lit with the same lighting intensity throughout. Over-lighting wastes
energy and money without producing any benefit. There are national and international
standards that recommend appropriate lighting levels for various tasks, and the following
table provides a first orientation (but each time the national standards should be used.
1 ‘Standard’ means a fluorescent lamp (tube) which is not a tri-phosphor lamp. Compared with a triphosphor
lamp, a standard fluorescent lamp has a shorter life (i.e. 8,000 hours compared with 16,000-24,000
hours), lower efficacy (lower light output for the same electrical power draw), poorer light colour, and
quicker performance degradation (aging).