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October 3, 2012 -
Today's tip is to look at your exterior lighting as a source of savings. Turning off exterior lighting loads for institutional and commercial facilities is the most effective way to save energy, but it might not address the lighting needs of the general population. People need some form of exterior illumination to feel safer and more secure. Beyond functional lighting, people also need lighting that enhances the nighttime atmosphere to encourage activity and make spaces feel inviting.
Every year, building codes and green building programs require that facilities further reduce energy consumption. Advances in technology have reduced loads for interior building lighting, but only recently have manufacturers considered extending these energy savings to outside.
Because organizations use exterior lighting to provide security and aesthetic appeal, it is no surprise that managers hesitate to turn off outside lights. But the lighting system for a parking lot designed in 1970 — or even 2000 — probably is outdated by today's standards.
Replacing the key components of a high-pressure-sodium fixture with LED lamps might reduce energy consumption and deliver a reasonable payback of two-four years — or, with rebates, instantaneous payback. Managers should be sure to specify LED sources from reputable, established manufacturers who have controlled binning standards, proven heat sinks and fixtures specifically tested and designed for their LEDs.
The most efficient LEDs are cooler white. In exterior applications, cool blue color temperatures also can result in reduced allowable lighting levels. But at least in the United States, cooler light — usually anything greater than 4,100 Kelvin (K) often is perceived as uncomfortable, sterile, and institutional. Building facades appear more inviting when illuminated with a warmer light — 3,000-3,500 K — that also has a high color rendering index (CRI). A CRI greater than 80 makes the finishes of materials and objects appear more true and rich.
Managers also should take care should to select a lamp that is compatible with the project's geographic location and the connected controls. Fluorescent lamps do not like low temperatures. Dimming ballasts also generally are not fond of temperatures below 50 degrees. Induction lamps are more compatible in cold environments, tend to produce less glare, and have one of the longest life spans. But they are not dimmable, and their distribution patterns can be difficult to control through fixture optics.