Task Lighting Solutions: Their Economic and Ergonomic Benefits

Supported by human factors research and driven by demand for energy savings, task lighting is a critical component of efficient and effective workplace lighting solutions.

November 2007
[ Page 3 of 9 ]
Educational Advertising Section Provided by Humanscale

By Karin Tetlow

The Monitor–Document Conflict

“The demands of differing tasks within the workplace create an obvious conflict in lighting requirements,” says researcher Alan Hedge, Ph.D., CPE, Director of the Human Factors and Ergonomics Laboratory at the Cornell University Department of Design and Environmental Analysis. The majority of work that most office workers perform today is a combination of viewing a monitor and reading documents or other printed material. Yet these two tasks require significantly different levels of light because monitors are a source of light whereas paper reflects light. In fact, reading documents requires four to five times the amount of light needed for viewing a monitor.

 

 

SmithGroup: Task Lighting Essentials

For Detroit-based SmithGroup, Inc., an A/E firm with its own in-house lighting design group, according to James Luckey, AIA, Senior Design Architect, a main goal with creating a nine-building campus in Van Buren Township, Michigan, for auto parts supplier, Visteon Corporation, was to attain “the absolute minimization” of energy costs. The first consideration was natural light. To allow as much light as possible into interiors, Luckey designed all of the 100,000- to 150,000-sq-ft buildings to be “…extremely narrow, 64 feet in width. We wanted this project to conform to the European standard, in which workers are never more than 10 meters from a window,” he said.

Exposures are large: sills of 15-ft-wide windows are only 2 feet above floors; headers are 10 feet above floor height; ceilings at 1-ft 6-in. above the headers. We like, whenever possible, to push ceiling height,” says Luckey.

Ambient lighting, via indirect pendants (95 percent upward, 5 percent downward), centered in 20-ft ceiling bays, 30 inches beneath ceilings, is at 25 to 30 footcandles and blends perfectly with the distribution of natural light. The uniformly illuminated ceiling plane increases the sense of openness and maximizes the impact of the high ceilings.

For “sparkle,” SmithGroup used café and track lights. Each 50-square-foot workstation has one adjustable compact fluorescent task light and one furniture-mounted fluorescent light capable of providing 50 footcandles where it is needed.

“The use of task lighting allows higher intensities only where that level of light is needed, while also providing the benefit of personalized control,” says Luckey. “In a computer environment, the goal is to minimize glare. This project,” he says, “is in keeping with what we try to do with every project. If ceilings are shallower, we have no choice but to put lights in the ceiling plane, but we prefer not to.”

At Visteon’s new corporate campus, which opened in January 2006, workers have personal control over lighting within individual workstations; individual controls allow them to control floor-distributed heating and cooling as well.

“Overall, lighting consumption,” Luckey says, “is one watt per sqare foot; lighting and miscellaneous power consumption, 2.25 watts per square foot—the figure excludes air-handling.

Perhaps more importantly,” Luckey says, “ASHRAE 90.1 sets a standard of 94,842 BTUs (British thermal units) per square foot per year. Visteon Village consumes about 59,000 BTUs per square foot per year—a 37 percent energy reduction from the code allowance. That number includes under-floor heating and cooling consumption.”

 


The SmithGroup delivered 25 to 30 footcandles of ambient lighting for the Visteon Corporation Michigan campus.
Photo courtesy of Justin Maconochie Photography

 

If the ambient lighting level is set at the appropriate level for reading printed documents (20–50 footcandles), the lighting intensity will be much too high for proper monitor viewing (5–10 footcandles required). This leads to glare on the surface of the monitor, substantial energy waste and a variety of worker productivity issues. However, if the ambient lighting level is brought down to a point which is appropriate for monitor viewing and movement throughout the workspace, then there won’t be nearly enough light to read documents and other paper-based reading material.

The only solution to this conflict is to lower the overall ambient lighting levels and provide individuals with positionable task lights to properly illuminate the reading material on the desktop. In this way, both the monitor and documents can be lit to appropriate levels for the tasks being performed.

 

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[ Page 3 of 9 ]
Originally published in the November 2007 issue of Architectural Record.

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