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Peter Walsh, PE
Lighting terminology can be challenging if it's unfamiliar. Some terms are old and well known; some are relatively new. For instance, lighting fixtures were renamed several years ago to luminaires. This was only a name change. Other terms are less obvious.
CRI refers to Color Rendering Index. It's a measure of how accurately an artificial light source displays colors. For instance, a pumpkin pie looks orange illuminated by sunlight or an incandescent light. When the room is lit by a typical compact fluorescent lamp, the pie has a greenish hue, which could depress one's appetite. Energy Star rated commercial fluorescent luminaires all have a minimum CRI of 80%. A higher CRI rating makes the colors appear more accurately.
The lumen is the basic measure of light intensity. A typical 60-watt light bulb gives off 855 lumens, which is 14 lumens per watt. This compares to a typical commercial fluorescent lamp that gives 80 lumens per watt. The lamp is only one component of the luminaire.
The LER (Luminaire Efficiency Rating) shows the total lumen output from the luminaire compared to the watts required to operate it. This is a convenient rating to simplify the combined performance rating of the lamp, ballast, and optics.
Energy rebate requirements are restricting the lighting watts per square foot of floor space. Using luminaries with a higher LER helps to attain the building owner's requirements.
Lightolier recently introduced their GO-2 high efficiency luminaire with an 85.9 efficiency rating. With larger commercial room sizes these fixtures can deliver good lighting levels at 0.6 watts per square foot. These luminaires can save 44% of power costs compared to traditional parabolic luminaries.
Photo courtesy of Lightolier, a Royal Philips Electronics Company
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