In certain applications, such as lobbies, corridors, and stairwells, lights must remain on for safety reasons, even when spaces are not occupied. Such spaces offer managers opportunities to reduce light levels and generate savings.
Consider an exit-stair area. Generally, a two-lamp fixture at each landing provides lighting in these areas. Since these are required exits, they usually have no switches, and the lights are on 24/7. Some fixtures use integral occupancy sensors to control one lamp in the fixture. For example, when the stair area is unoccupied, which is most of the time, only one lamp in each fixture is on. When a person enters the stairwell and triggers the sensor, the other lamp comes on.
Increasingly, the idea of reduced light output is making its way to the exterior environment. Historically, options for exterior lighting control have been simply on or off, and they have used a photocell or timer control for automation. Today, some metal halide and LED sources are dimmable, so managers can set them at reduced output levels.
This strategy can offer significant benefits in parking lots, where reduced spot lighting can make an area feel unsafe. At times of low use, a uniform reduction in lighting is acceptable and results in significant energy savings.
For interior and exterior applications, an alternate strategy might be more effective and beneficial over the long term.
Designers intentionally overdesign most lighting systems so near the end of life, when the output of the source drops, the system continues to produce enough light.
Dimming the system when it is new can reduce the light to the desired level, and gradually increasing output over time maintains that level. Because the system remains dimmed for the duration of the time, the strategy saves energy.
In office spaces, studies reveal that if occupants can control their lights, they are more satisfied. They often set lights at less-than-full output, generating additional energy savings. In spaces that already feature photocell dimming, adding personal dimming is often a low- or no-cost benefit.
For large buildings, technicians can monitor a control system using a web-based program, allowing them to collect energy data and fine-tune lighting energy use. They can see if a room is occupied when not scheduled for use, get reports on components that need servicing, and see when the service is complete.
The programs reduce the need for random room checks and technician response time. The situation reduces maintenance costs and boosts user satisfaction because technicians can make repairs more efficiently.
Wireless controls are available that further reduce the cost of implementing controls in an existing facility. Some even use kinetic — motion-generated — energy, which eliminates the need to replace batteries.
Wireless technology allows managers to implement occupancy-sensing controls and even photocells with little or no rewiring. This strategy is especially valuable in retrofits.
Denise Fong, IALD, LEED AP, is principal of Candela, a lighting consulting and design firm in Seattle. She has more than 25 years of developing award-winning lighting designs in the built environment.
Spotlight: Lighting Controls AssociationThe Lighting Controls Association (LCA), administered by the National Electrical Manufacturers Association (NEMA), is dedicated to educating the professional building design, construction, and management communities about the benefits and operation of automatic switching and dimming controls. These benefits include energy savings, flexibility, and higher-quality building environments. LCA members include noted leaders in the manufacture of advanced controls and dimming ballasts. Services include free, 24/7 access to white papers and articles, education courses, projects, and a monthly newsletter. For more information, visit www.aboutlightingcontrols.org. |
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