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How can we increase the energy efficiency of our office lighting?

The lighting fixtures most commonly used in commercial settings today are T8 lamps and ballasts, says Gregory Crew, president of GreenOrder. It is possible, however, to further increase lighting energy efficiency through the use of newer T5 lamps. These lamps deliver more light for fewer watts than T8 lamps. In fact, standard T5 lamps are 12% to 18% more efficient than T8 lamps, averaging about 96–106 lumens per watt. High output T5 lamps generate nearly twice the light output of standard T5s, as well as T8, and T12 lamps.

In addition to the energy savings, it has been estimated that T5s:

• Require 40% less glass than T8s
• Have 80% less mercury content (3mg versus 15mg)
• Have improved lumen depreciation (light stays at or close to full light output longer), so need to be replaced less frequently

However, while more efficient, T5s are not necessarily the best choice for all applications. Because the lamps tend to be brighter than comparable T8s, glare can be a problem in lower ceiling height areas where direct lighting is the desired goal. T5s deliver the best light quality when used in indirect lighting applications, or direct/indirect fixtures that shine light upward against the ceiling and downward into the workspace.

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