Wendy McNamara doesn't dread Monday mornings anymore. Or Monday nights, for that matter. The 26-year-old insurance underwriter leaves the office after a hard day's work feeling refreshed, not lethargic, and her two-hour commute is actually pleasant. "When I get home, I'm more relaxed and in a much better mood," she says.

McNamara's managers at insurance company Magna Carta have unlocked one of the secrets to keeping her and her co-workers happy. Sure, an annual bonus and raise help, but one overlooked key to pleasing employees is good lighting. McNamara used to spend her days cooped up in a dark cubicle, donning anti-reflective glasses to shield her from glaring lights above and wondering whether the sun was shining outside. Now, after an ambitious overhaul of Magna Carta's New York City office by design firm HLW, she has shed her spectacles and enjoys sunlight from her workspace. "I wouldn't mind eating lunch at my desk now," she says.

Lighting was on everyone's shortlist when Andrew Furgatch, chairman and chief executive officer at Magna Carta, and David Lawless, the company's senior vice president, conducted employee focus groups on office improvements. That's no surprise, since bad lighting can make workers grumpy, nervous, sleepy, or miserable. Victims of really bad lighting skulk in late, take extended lunch hours, and call in sick more often. "That could mean one less phone call, e-mail, or transaction a day," notes Lawless, who supervised the redesign. Multiply that by the company's 250 employees, and say goodbye to a chunk of potential revenue.

Most employees don't realize why lighting affects their moods, but the reasons are simple and physiological. When light enters the eye, the retina sends signals to the pineal gland to suppress production of melatonin, the sleep-inducing hormone, while increasing the production of energy-giving serotonin. Give people too much light, and they'll eventually become disoriented (think Al Pacino in Insomnia); take away light, and they'll show signs of depression (think any Ingmar Bergman movie). "You want something in the middle -- right in the bright, cheery range," advises Dr. Alan Hedge, a pioneering ergonomics specialist at Cornell University.

Lighting also affects co-workers' perceptions of each others' appearances -- and thus even their personalities. The rectangular fluorescent recessed fixtures standard in many offices cast shadows on the face, creating a shifty-eyed appearance, according to Hedge.

A bulb's wavelength, as determined by its color temperature, can also play odd tricks on the eye. Cool white fluorescent bulbs, with their bluish hue, narrow the pupil. They're great for sharpening the eyesight and ideal -- in theory -- for above-desk placement. But, Hedge cautions, they may make even your most attractive co-worker look as beady-eyed as Peter Lorre. Consider conducting important meetings under warmer incandescent or fluorescent lights. They cause pupils to dilate -- which makes for a more appealing look.

At Magna Carta, daylight-blocking perimeter offices met with the wrecking ball, opening up even center cubicles to natural light. HLW senior associate Heidi Schenker, who managed the project, then had the cubicle area's harsh interrogation-type lighting replaced with one-foot-wide fluorescent fixtures that span the length of the space, suspended from the ceiling with 18-inch-long cables. They diffuse light both up and down, creating a more natural, sky-like glow. Designers and ergonomics experts agree that these fixtures are especially beneficial in open areas with few windows. (A study Dr. Hedge conducted at a window-deprived Xerox office revealed that employees working under similar lights reported half as many daily health complaints like headaches and eyestrain than those directly under recessed lights.)

When the Magna Carta staff returned to its renovated office, the lighting got rave reviews. Looking jovial and relaxed in his own office, where the gently diffused overhead light mingles with natural rays from the window, Lawless acknowledges that spending a couple hundred thousand dollars on lighting was well worth the expense. "Everyone's a little happier now," he says. "Including me."

Quick Fixes

If you lack the time or money to totally revamp your gloomy office, fret not. Experts offer several shortcuts to a cheerier milieu. For one, turn it down, says Steven Orfield, founder of research and design firm Orfield Labs in Minneapolis. If you're stuck with a glaring multibulb fixture overhead, climb that ladder and take one or two out. Paint dark walls a bright white, or even yellow, and remove upper cubicle panels. Ergonomics expert Dr. Alan Hedge of Cornell University has killed the overheads in his poorly lighted Ithaca, N.Y., office and replaced them with moveable-arm lamps and torchÈres to lighten the mood. Vivian Loftness, head of Carnegie Mellon University's architecture school, suggests upgrading buzzing and flickering fluorescent lights by replacing their dated magnetic ballasts (the part that stabilizes the current in a circuit) with new electric ones.

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