The Ups and Downs of Lighting

03/26/2003 |

Deciding Between Direct and Indirect Lighting

Clean, light-colored furniture works best with all lighting systems and maintains a comfortable working environment.

Being a facilities manager, chances are you’ve heard a building occupant complain of fatigue, blurry vision, headaches, or back and neck pain. Before you call the doctor, consider your building’s lighting system – it could be to blame. With 68 percent of employees complaining about the lighting in their workspace, facilities managers are constantly being challenged to re-evaluate their current lighting situations.

Most professionals recognize the obvious differences between direct and indirect lighting systems – but there are other benefits, drawbacks, and points to consider before deciding which is best for your particular situation. No single type of fixture is appropriate for every application.

Direct Lighting

Direct lighting luminaires are typically recessed into the ceiling and aim 90 to 100 percent of their light downward from the ceiling onto the worksurface. A small amount of reflection may occur due to light hitting the wall, but the majority of the light hits the space without any reflection. High in popularity, you’ll see this type of lighting in most office spaces today. Many manufacturers provide lenses or louvers to shield the actual lamp from view and cut down on glare. Direct lighting can produce visual “excitement” and create visual variation. In most cases, the fixture cost is less with a direct lighting fixture than an indirect fixture, and installation is easier considering many of today’s traditional grid ceiling systems. Depending on an employee’s task, direct lighting may prove superior.

On the flip side, direct lighting can create an “uneven” environment if fixtures are not spaced properly. It can cause shadows in the space: Employees sitting under the fixture may receive very high levels of light (sometimes even too much), while others seated away from the fixture may receive much less (sometimes too little).

Office furniture must be clean and light-colored in order to reap optimum benefits from the fixtures. Darker-colored furniture or partitions can absorb lighting, making it hard to maintain a good balance of brightness for the user.

Some direct fixtures, like those with plastic lenses, can create glare on computer screens. This can contribute to blurry vision, fatigue, and headaches. Too much overhead light can create direct glare and visual discomfort. Eye fatigue can also result from uncomfortable differences in “visual brightness” in the work environment.

Additionally, cleaning and maintenance can be a hassle with these lighting fixtures. Maintenance workers may have to climb ladders to reach the fixtures; if lenses and louvers aren’t hinged, the piece must be removed and set down before workers can install the new lamps. Lenses and louvers must be cleaned, as well as the interior of the fixture’s housing.

Indirect Lighting

Indirect lighting fixtures are typically suspended from the ceiling on pendants or aircraft cable, and they aim 90 to 100 percent of their light upward. The light hits the ceiling and is reflected back down onto the workspace. Terry Clark, president at Union City, CA-based Finelite Inc., explains that the indirect lighting market is breaking into two segments. “There’s one [segment] that deals with a lot of architectural pizzazz. You’re buying style, you’re buying a brand name … they often offer custom lengths, and perhaps shapes. You pay a substantial premium because these fixtures are hand-crafted, high-margin products. The second, and fastest-growing segment, is for affordable, easy-to-install fixtures made in high volume. These fixtures often can be installed for less than half the cost of the architectural ones. If a customer is being told that indirect lighting is too expensive, they may be looking at the fixtures in the architectural segments instead of high-volume ones, or the contractor may not be aware of how easy the newer-style fixtures are to install,” Clark explains.

Although indirect lighting isn’t used as often as direct lighting, its popularity is increasing in commercial office facilities. It’s proven that employees tend to prefer indirect lighting in the work environment due to the increased visual comfort. “We get thousands of people that come through the Lighting Institute, and [there] we have an office lighting demonstration room. We’ll show them direct lighting systems with lenses and parabolic louvers. Then we’ll show them an indirect lighting system in the same space, and almost without exception, people tend to prefer indirect lighting just because it’s visually very comfortable and gives a very pleasant glow to the space,” notes Mary Beth Gotti, manager, GE Lighting Institute, Cleveland, OH.

The light is shadow-free and evenly distributed; everyone in the space receives the same amount, regardless of where they’re seated. This allows office furniture to be moved and rearranged without having to take the lighting fixture locations into consideration.

“Probably one of the best advantages of indirect lighting is that it does give the illusion of more light,” says Gotti. “As everyone is struggling to get watts-per-square-foot down for their lighting systems, [indirect makes] the space appears brighter than what it is. You probably can get by with a bit less lighting because the quality of lighting is so good. Some of the lowest watts-per-square-foot can be achieved with some of today’s indirect lighting systems.”

Maintenance is also convenient with indirect lighting. Fixtures can sometimes be reached without a ladder. It can be a simple process of removing the bad lamp and replacing it with a good lamp; no pieces need be removed or set down. Surfaces still need to be cleaned, as with direct fixtures.

Common complaints about indirect lighting are that it is “uninteresting” or “gloomy” since it doesn’t create much visual excitement or variation. Emphasis isn’t placed on any certain area, and nothing in particular is accentuated.

To obtain maximum advantage from an indirect system, your building’s ceiling material must be at least 70-percent reflective, or preferably 80-percent or higher reflective. In recent years, ceiling material made with 90-percent reflectance has been made available. Peter Ngai, vice president of product development, Berkeley, CA-based Peerless Lighting, explains that ceilings shouldn’t be made of specular-type materials. “If you have a mirror-finish type of material, that’s not very good for indirect. You actually will be able to see the lamp images in the reflection.”

Ceilings must be light-colored and clean. “If you have a paint color that’s not white, you’ll reflect some of that color down. For example, if you have brown paint and reflect white light up, some of the brown light will come back down. Something will bounce off,” explains Steve Goldmacher, director of corporate communications, Somerset, NJ-based Philips Lighting.

As mentioned with direct fixtures, indirect fixtures also work best if office furniture is clean and light-colored.

Although installation and fixture costs have previously been thought to be higher than direct luminaires, popularity and familiarity are lowering expenses. And fixtures are not only becoming cheaper, they’re becoming easier to install.

Energy Efficiency

Energy efficiency is always an issue when buildings professionals talk about lighting. Both direct and indirect systems have things to keep in mind when contemplating energy usage.

Direct lighting can be an efficient option. Gotti points out that efficient lamp and ballast combinations can be used in these luminaires. The New York City-based Illuminating Engineering Society of North America (IESNA) recommends certain footcandle levels for various tasks (writing, typing, reading, etc.). “To achieve that level with reflected light may require more initial lumen output from the lamps if they have to reflect back before [hitting the required level],” explains Goldmacher. In other words, it may take more actual light output from an indirect fixture to equal the same footcandle level as the light output from a direct fixture.

Indirect fixtures can be an efficient choice as well. Instead of having to feed each light separately, continuous pendant systems require only a single point for an electrical feed. And because of the high intensity and smaller diameter of T5 fluorescent lamps, indirect fixtures can be more efficient and spread farther apart, which lowers watts-per-square-foot. “If you can get your watts-per-square-foot down, the energy savings may more than pay for the difference in going from direct to indirect lighting,” emphasizes Gotti.

To meet the tightest energy codes (approximately eight-tenths of a watt-per-square-foot or lower), Clark estimates a building owner will need at least 15- or 20-percent downlight.

Although no one answer fits every building, think about the lighting system your facility currently has, look at your possible options, and take these points (as well as those in the “Deciding Which Light is Right” section) into consideration during your quest to make your facility its best.

Leah B. Garris (leah.garris@buildings.com) is editorial coordinator at Buildings magazine.


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