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Part 3: Balancing Lighting Quality With Energy Efficiency
By Lacey Muszynski, Assistant Editor
December 2008 -
Striking a balance between energy efficiency and lighting quality is what will produce the best lighting system possible. “Efficiency is in the eye of the beholder,” says Steffy. “Although facilities can implement very austere sustainability practices and achieve low energy bills, if occupants are dissatisfied or unable to work optimally, the savings and sustainable prestige are false positives.”
A popular step in saving energy costs on lighting is lighting controls. However, the controls, especially motion sensors and automatic shut-offs, have sometimes frustrated occupants. This is generally because occupants have not been properly educated on how the controls work, what to expect and how to operate them properly. “The most important thing you have to do is educate the user,” says Graf. “The first thing they’re going to do is complain that the lights are off.” An easy way to prevent this is to post signs around the facility or near the lighting controls explaining the need for them, what to expect and how they benefit the facility.
Another way to give occupants more control over the lighting to accommodate different needs is to implement a lighting strategy incorporating layers of light. A space like an office is usually divided into three layers: ambient light, or the light that illuminates the bulk of the space, generally by overhead fixtures; task lighting, which is stationed in specific work areas; and accent lighting, which adds interest to the space. By keeping ambient light levels relatively low, facility executives allow occupants to decide if ambient light is enough or if they’d like to turn on task lighting. That way, each occupant uses only the amount of light necessary, keeping energy costs lower.
Perhaps the biggest asset to both sustainable lighting systems and occupant satisfaction is daylighting. “Nothing is more energy efficient than free,” says Graf. Therefore, take advantage of every possible source of daylight available. “We have to start utilizing the free natural resource of daylight in good lighting design,” he says.
That doesn’t mean, however, that facility executives should just let daylight stream in windows and skylights without carefully considering it as part of the entire lighting design. Daylight should be integrated with electric lights so they work in tandem to keep the lighting levels appropriate in the space. Shading systems, louvers, light shelves and photo-sensor lighting controls that automatically dim the lights can all be elements of a successful daylighting strategy.
“Daylight and artificial light can work together quite well, providing that glare is satisfactorily addressed and automated systems are installed,” says Steffy. Everyone has had the experience of walking through an airport, mall or other public building and noticing the lights are on in the middle of the afternoon while daylight is streaming in through the windows or skylights. That’s exactly what facility executives are trying to avoid when they install dimming controls.
To avoid complaints or confusion, it’s important — as with occupancy sensors — to educate occupants about how to operate the dimming controls and what to expect when they’re operating properly. When operating as designed and commissioned, daylight dimming systems are one of the greatest assets to energy efficiency in a building, says Kahn.
Integrated daylight dimming systems may not be as easy to implement as a simple across-the-board relamping project, but the benefits to the facility’s bottom line and the occupants of the space far outweigh the time and effort required. “When thinking about implementing an energy efficient lighting system, facility executives need to lay out a strategy that is appropriate for the space and go for the investments that make sense for the long term,” says Kahn, “not just the low-hanging fruit which may turn out to be rotten.”
Energy Efficient Lighting Systems
Part 1: Performance Metrics For Lighting Systems
Part 2: Lighting Quality Metrics: CRI And Temperature
Part 4: EPAct Tax Deduction Extended