Office lighting remains one of the most hotly debated topics among facility managers in institutional and commercial facilities. Managers, along with lighting product managers and manufacturers and researchers, bring a variety of opinions, insights and experiences to discussions about the most effective way to light a range of office spaces in order to address such priorities as worker productivity and energy efficiency.
In one of the latest developments, researchers from the Lighting Research Center at Rensselaer Polytechnic Institute and the U.S. General Services Administration (GSA) recently published a study exploring the way light impacts alertness during the day and sleep quality at night in daytime office workers.
The study field tested a luminaire developed by the center to promote circadian entrainment and alertness in the office environment. Nineteen participants from three U.S. Department of State office buildings in Washington, D.C., completed the three-week study. The luminaires, mounted near the participants’ computer monitors, provided:
• morning saturated blue light delivering a circadian stimulus (CS) of 0.4
• midday polychromatic white light delivering a CS of 0.3
• afternoon saturated red light delivering a CS close to zero.
The study’s results show that participants exhibited more consolidated rest–activity patterns, indicating better circadian entrainment and woke up earlier during the intervention compared to baseline. The morning blue light appears to have advanced participants’ circadian phase, causing participants to wake up earlier in the morning. The afternoon red light elicited an acute alerting response close to the post-lunch dip around 3 p.m., reducing subjective sleepiness and increasing subjective vitality and energy.
These field results are the first to demonstrate that red light in combination with ambient white light provides an effective alerting stimulus and to support the inference that properly applied light exposures can promote circadian entrainment and increase alertness.
Previous studies by the center measured light levels for 109 participants at five federal office buildings designed to maximize daylight availability indoors. Researchers found that even in open offices with many large windows, office workers did not receive enough light to stimulate their circadian system during the day, due to factors such as season, cloud cover, desk orientation, and window shade position.
Dan Hounsell is editor-in-chief of Facility Maintenance Decisions.
