An Easy Way to Improve a Building's Efficiency
Lighting Controls
Additional Benefits
Cost Effectiveness
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An Easy Way to Improve a Building's Efficiency
Artificial lighting accounts for a substantial portion of the electricity used in
buildings. Daylighting is the effective use of natural light in buildings to
minimize the need for electric light during daylight hours. Increasing levels of
daylight within rooms can reduce electrical lighting loads by up to 50% in some cases. A
well daylit building can often provide sufficient natural light for general work
activities for a substantial part of the year. The amount of energy savings that can
be realized through daylighting will be affected by factors such as building shape,
building orientation, building materials used, and the orientation of work areas in
relation to windows. Also keep in mind that with daylight comes heat. It is
important to avoid overheating that may stem from excessive direct daylighting by
using window coverings such as drapes, shades, and blinds. |
Lighting Controls
Daylighting will not reduce energy consumption unless users turn off or reduce the use of
unnecessary artificial lights. This can be achieved by using lighting controls.
Lighting control systems can provide constant lighting levels by blending artificial
lighting with daylighting to improve building energy efficiency. Lighting control options
include on/off switching, dimmers, and multi-level cut-off systems. Manual on/off
switching, timers or occupancy sensors are simple systems with a low to moderate cost.
Occupancy sensors use infrared detection or ultrasonic wave detection. Dimmers and
multi-level cut-off systems are typically more complex and more costly. Multi-level
systems may involve wiring different groups of lights together to operate off sensors with
different settings. Dimmer systems require special ballasts when fluorescent or high
intensity discharge lamps (HID) are involved. Some controls integrate daylighting sensors,
which use light detection with occupancy sensors, which use motion detection, into a
single package. All three systems operate manually or automatically.
Additional Benefits
Besides energy savings from reduced lighting loads, there are other indirect benefits from
daylighting. Human health and productivity can be enhanced with sound daylighting
designs. Some studies have indicated significant increase in productivity (up to
15%) and reduced absenteeism for office workers through the use of effective daylighting.
Recent studies in California demonstrate a strong statistical correlation between
daylighting and improved sales in retail stores. Similarly, daylit classrooms are
being shown to result in faster learning and healthier students.
Cost Effectiveness
Effective daylighting design involves balancing the elements of artificial lighting, solar
heat gain, heat loss through glazing, and internal sources of heat gain. Daylighting must
be integrated with electric lighting, heating, cooling, and ventilation systems as well as
occupant task and movement patterns. Successfully doing so will provide a more comfortable
and energy-efficient building. Whether you are designing a new building or retrofitting an
old one, you need to perform extensive computer modeling and simulation. To be
cost-effective, the savings on lighting and cooling must offset the costs of buying,
installing, and operating daylighting features in a reasonable amount of time.
Sources: US DOE FEMP "Greening Guidelines", US DOE NREL "High
Performance Building Research: Daylighting", US DOE EREC "Daylighting for
Commercial, Institutional, and Industrial Buildings"
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