Lighting Control for Existing Buildings

June 8, 2009
Lighting is a target for energy-efficiency improvements because it's profitable

As building owners shift their resources from new construction to upgrading existing buildings, lighting will be a target for energy-efficiency improvements because they’re profitable: The average lighting upgrade generates a payback of 2.2 years and a 45-percent return on investment, according to the Energy Cost Savings Council.

According to the New Buildings Institute, advanced lighting controls can reduce lighting energy consumption by 50 percent in existing buildings, and by at least 35 percent in new construction. In an existing building, the most profitable control opportunities come from upgrading existing controls and ballasts with minimal rewiring …

Occupancy sensors. These devices take the switch and automate it with a sensor that tells the switch to turn the lights off when it detects the absence of people. Many models are available that also turn lights on automatically when the sensor detects people, but manual-on sensors produce higher energy savings. Occupancy sensors are ideal for intermittently occupied private spaces with an unpredictable rate of occupancy, as well as aisle lighting and outdoor security lighting. They’re quite common in new construction because of automatic shutoff requirements in energy codes.

According to the New Buildings Institute, occupancy sensors can produce 35- to 45-percent energy savings in offices, and 25-percent energy savings in classrooms. The easiest upgrade is to replace wall switches with occupancy sensors in smaller, enclosed spaces. If the space already has bi-level switching, the two wall switches can be replaced with a bi-level manual-on/auto-off or auto-on-to-50-percent/auto-off occupancy sensor for even higher savings. And, if the sensor needs to be installed somewhere other than the location of the existing wall switch, a wireless occupancy sensor could be used.

Load scheduling. Existing lighting panelboard can be upgraded to enable scheduling capability, which can generate 5- to 15-percent energy savings, according to the California Energy Commission. This type of upgrade poses little impact on operations and provides solid energy savings; like occupancy sensors, load scheduling is a frequent feature in new buildings because of automatic shutoff requirements.

Load scheduling also makes it easier for lighting to participate in demand response. Opportunities may be limited by the number of loads that can be switched while the building is occupied; dimming is often ideally suited for demand response.

Dimming. Dimmable electronic ballasts are now as efficacious as instant-start ballasts. For the most efficient ballasts, look for the NEMA Premium label.

Ballasts may communicate with control devices using existing line-voltage (power) wiring or newly installed low-voltage (control communication) wiring. Ballasts that communicate using power wiring present the most economical option for retrofit.

Some ballasts communicate wirelessly with handheld infrared remotes, enabling users to control their own light fixtures. This strategy correlates with increased job and environmental satisfaction while producing about 10-percent energy savings.

Once dimmable ballasts are installed, a number of other strategies are possible, such as daylight dimming control (which produces 35- to 60-percent energy savings, according to the New Buildings Institute) and demand response.

If demand response is employed, lighting can be dimmed in select areas or across entire buildings in response to a schedule, pricing signal, or utility request. Demand charges can represent 25 percent of energy costs. According to research conducted by National Research Council Canada, most occupants are unlikely to notice dimming of light levels by 20 percent (with rapid response, over as little as 10 seconds) in spaces with no daylight, and by 60 percent in spaces with high amounts of daylight.

A good lighting-control system satisfies design intent and operational needs. This often involves meeting visual needs by providing flexibility, and minimizing energy consumption by eliminating energy waste. In an existing building, controls can generate dramatic energy savings for a reasonable cost addition to the total lighting upgrade cost while satisfying users. The best approach for your building will depend on your needs and economic interests.

Craig DiLouie, principal at ZING Communications Inc., is a journalist and educator who specializes in the lighting and electrical industries.

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