Efficiency Goals

May 1, 2009 12:00 PM, By Donald Graham

Education institutions can save energy with smart lighting choices.

The lighting of learning environments is an important focus in designing new schools and renovating older schools. Studies long have shown that appropriate lighting levels and daylighting improve learning; now, climbing energy budgets have spurred school administrators to seek more efficient use of lighting.

Electricity rates are expected to rise over the next several years. That makes efficient lighting design and control strategies even more critical. According to a major lighting controls manufacturer, lighting can represent up to 55 percent of an education facility's electric use. For the average school in the northern United States, lighting represents 15 percent of overall energy costs. The good news is that improved lighting efficiency and controllability can yield energy savings of up to 40 percent; some new products are touting energy savings as high as 60 percent.

Some states — including Alabama, Florida, New York and West Virginia — now are making grant monies available to schools for energy-efficient designs.

New school designs are taking advantage of rapid improvement in lighting-control strategies and illumination systems, and existing schools can be retrofitted to realize savings.

Controlled lighting

The three most prevalent energy-saving tactics are increased use of daylighting, maximum controllability and prudent selection of lighting equipment.

• Daylighting

  The more that natural light floods a classroom, the less artificial light is required. Studies have shown that where natural light illuminates classrooms, student achievement improves. But for daylighting to improve learning environments, it must be controlled appropriately. Glare and solar heat gain can create an uncomfortable classroom environment and negate the advantages of natural light.

  Shading devices on windows can reduce glare and heat gain. Light shelves, mounted either internally or externally, can bounce sunlight from reflective surfaces upward and deeper into the classroom, thereby distributing light evenly. Light shelves generally are used to shield and disperse light coming in from south- and west-facing windows. The heat energy that light shelves add to a classroom is on the same order as that generated by ceiling mounted fixtures.

  Interior light shelves generally are mounted between 6.5 feet and 7 feet high, which is safely above head height. This leaves the bottom two-thirds of a window exposed to direct sunlight. To diffuse glare and dampen heat gain, shades or diffusers can be installed within windows or on the interior. Some shades and diffusers will admit a majority of the natural light into a classroom while reducing heat gain and glare.

  The cost of interior light shelves averages about $1,500 per classroom, resulting in a payback of more than 15 years in energy savings. Although adding light shelves may not result in short paybacks, it does improve the lighting environment by enhancing uniformity and penetration of natural light.

  In contrast, new glazing technologies can greatly reduce solar gain. The low-E family of glazing may work in concert with shades, or may even eliminate the need for shades. Some glazing technologies also have insulated double panes filled with argon gas to reduce energy loss. The glass also may be finished with a low-E coating, which keeps interiors warmer in the winter and cooler in the summer, and helps protect interior furnishings from fading.

  Low-E solar-control glass is good for hot climates because, in addition to improving the insulating ability of windows, it also limits solar heat gain by blocking passage of infrared and some ultraviolet spectrum light. Solar-control glass allows a higher level of visible light to pass through a window with less solar heat gain than tinted window coatings. Glazing with a low visible light transmittance (VT) value can be used in applications where direct sunlight is problematic.

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