Although lighting is critical for maintaining a comfortable indoor environment for staff, customers and visitors, it accounts for more than 20% of energy use in a typical commercial building.
A lighting upgrade can reduce operating costs substantially, but it should involve more than just selecting the most energy-efficient products available. Through careful planning and equipment selection, you can create a lighting system that optimizes visual comfort and makes the most effective use of the available space.
When choosing equipment, keep in mind the effectiveness of the overall system.
Lamps. Lighting technology is undergoing rapid change as traditional incandescent, halogen, fluorescent and high-intensity discharge sources are being replaced with solid-state LED lamps.
Sensors. There are a variety of sensors available to reduce the energy consumption of lighting systems. Occupancy and vacancy sensors use either infrared or ultrasonic techniques to detect motion in a space. Photosensors can be used with daylighting controls to dim or turn off lights when adequate natural daylight is available.
Fixtures. When upgrading, you can replace just the lamp, use a retrofit kit, or replace the entire fixture. Some lamps use the existing ballast and can be "dropped in" the existing fixture. Others require bypassing the ballast and wiring the lamp directly to supply voltage. New fixtures have a higher initial cost but deliver the best light quality.
Lighting system design
A lighting upgrade will have the most impact if the system is designed to match the specific needs of the application and space. Key considerations include light quantity, light distribution and color quality.
The quantity of light needed depends largely on the application or the tasks being performed. The Lighting Library®, published by the Illuminating Engineering Society, provides recommended light levels for a variety of applications and visual tasks. Space dimension, the availability of outdoor light and surface reflectivity are also important factors.
Direct down-lighting fixtures are commonly used because they provide good illumination at floor level, but they can also leave walls and ceilings dark and create glare. Indirect fixtures illuminate the ceiling and upper walls, where the light is reflected down. Indirect lighting improves visual comfort and illuminates areas using less light, but it is more effective in areas with ceiling heights of 10 feet or more.
Two measurements define color quality: correlated color temperature (CCT) and color rendering index (CRI). CCT describes the color appearance of white light; a low CCT creates a warm, relaxed atmosphere, like you would find in a public space, while a high CCT fosters a more focused environment, such as an office setting. CRI indicates how well a light displays colors on objects; the higher the CRI, the more accurately it displays colors.
Automatic lighting controls can reduce lighting cost by 50% or more. Control types include timers, occupancy or vacancy sensors, daylight harvesting, demand response and receptacle control.
The control types chosen for any given project depend on the building type and application. To optimize savings, use a layered approach combining multiple control strategies.
Optimize efficiency through system maintenance
The benefits of a lighting upgrade will not last long if the system is not maintained properly. Over time, lamps burn out, light output decreases, and dirt accumulates on lamps and fixtures.
Address maintenance at the beginning of the upgrade process. Simplify maintenance schedules by using as few types of light sources possible. Consider group relamping; not only does it save on labor costs over traditional spot relamping, it also ensures brighter, more uniform lighting.