Between 1984 and 2003, the percentage of people directly using a computer at work more than doubled to nearly 57 percent. The widespread adoption of computers not only changed office environments but also best practices in lighting and, by extension, office lighting technology. For example, lensed troffers produced high-angle brightness and, therefore, became displaced by parabolic fixtures, which use shielding at high angles. But as is the case with many lighting devices, there is a trade-off. These fixtures reduce glare on computer screens, but because the light they emit is concentrated almost entirely downward, with very little light reaching high walls or the ceiling plane, they often are accused of producing a dim atmosphere popularly described as the “cave effect.”

Today, the question of whether parabolics are actually needed is relevant. Today’s flat liquid-crystal display (LCD) screens are a far cry from yesterday’s glass screens with light characters on dark backgrounds. As a result, the problem of glare on computer screens has diminished with new-screen adoption.

A new type of recessed lighting fixture has emerged to take advantage of this program. Also called “volumetric lighting” after Lithonia Lighting introduced the RT5 line in 2004 (but also known as “full distribution lighting” or “diffuse lighting” by other manufacturers), premium troffers include Lithonia’s RT5 and RT8; Day-Brite’s Attune and SofTrace; HE Williams’ HET-T8 and HET-T5; Columbia’s EPOC, Zero Plenum Troffer and Energy Max Intersect; and Cooper’s Accord, Ovation, 2HP and Class R products.

A premium troffer is a fluorescent troffer with a photometric distribution including a small amount of light in the 60- to 90-degree zone, which smoothly fades as the angle gets closer to 90 degrees. You can find published photometric information on the manufacturer spec sheets for the products.

The light source, which may be T5, T5HO, T8 or compact fluorescent, is concealed behind diffuse shielding. Downward distribution typical of direct lighting is combined with light emitted in directions approaching horizontal that is more typical of indirect lighting. This combination produces several interesting results: First, light is distributed uniformly on high vertical surfaces in the space, making the space appear larger, brighter and more open while eliminating the cave effect. Second, shadows are softer, and facial recognition may be improved. Third, the light is distributed more uniformly, which is important when office workstations are moved around later.

Premium troffers compete with older parabolics, conventional troffers, new-generation parabolics, basket-type fixtures and direct/indirect fixtures in the office general lighting market. They also are appropriate for schools, hospitals, retail spaces and libraries (higher vertical uniformity is a positive attribute for places with racks or shelves), and other commercial areas requiring fluorescent lighting—particularly upscale spaces because of the fixtures’ enhanced architectural aesthetic.

Premium troffers not only are credited with improved visual comfort and lighting quality compared to older lensed and parabolic recessed fixtures, but they also have a good energy story. One argument goes like this: Since vertical light levels make people believe there is more light in the space, lower real light levels can be tolerated while satisfying users, creating opportunities to save energy (with fewer lamps). The new generation of premium troffers makes an even stronger case by using highly efficient lamp and ballast technology and increased fixture efficiency.

Another argument is this: These fixtures are designed with a fixed cross-section, meaning, for example, a two-lamp T5 fixture has optics optimized and designed exclusively for that lamp type and number of lamps. The product of this is higher efficiency (up to 90 percent), with light output modulated by changing the lamp based on light output or specifying a different ballast factor (low, normal, high). Some two-lamp premium troffers are efficient enough that they may produce comparable light output as conventional three- and four-lamp troffers, according to one manufacturer. The result is lamps can be shed—one-third to one-half, by one estimate—which reduces energy and maintenance costs, in turn helping to recoup the higher initial cost of the fixtures.

One manufacturer calls premium troffers the fastest growing segment of the lighting market—with demand high in both new and existing building projects—an accelerating trend as energy codes and sustainability concerns become more important.

For you and your customers, seeing may be believing, particularly where the visual comfort and lighting quality argument is concerned. At least one manufacturer offers a program enabling installation of its products for evaluation.

DILOUIE, a lighting industry journalist, analyst and marketing consultant, is principal of ZING Communications. He can be reached at www.zinginc.com.