Lighting strategies to optimize worker performance are alive and well. In fact, the correlation between lighting and human performance is now better understood than ever, and the knowledge is influencing manufacturers, lighting designers and savvy installers. The office is the latest subject.
While lighting and its effect on visual tasks (glare, visual acuity and comfort) have been studied for decades, further investigation of other physical, emotional and cognitive effects has deepened our understanding in how lighting influences how well we do our jobs.
Human and environmental factors research in the 1990s and early 2000s led by California’s Heschong Mahone Group (HMG) stands as landmark work. The correlations found between daylight availability and human productivity across multiple building types are recognized today. For example, HMG’s study of schools found significant improvements in test scores (21 percent) to be strongly correlated with daylight in classrooms. Its 2003 follow-up, “Daylighting in Schools: Reanalysis Report” with the New Buildings Institute (NBI), affirmed those findings, adding that effective lighting has “important implications for the design of schools and other buildings.” An HMG retail study found that sales were as much as 40 percent higher in stores with sky lighting. Designing schools, retail spaces and offices has never been the same.
Building the case
Picking up from HMG and other research, the Light Right Consortium was formed. Its mission was to investigate and educate lighting professionals on the relationship between high-quality, energy-efficient lighting and office worker productivity. Carol Jones, L.C., founded the consortium while at Pacific Northwest National Laboratory (PNNL) and managed its research. (PNNL is operated by Battelle for the U.S. Department of Energy). Jones is category project manager–Intelligent Office and Industry Systems for Philips Lighting NA in Massachusetts.
Looking back, Jones said, “I see three key findings as practices. Achieving room surface brightness using indirect lighting, wall washing and similar strategies is important. What you don’t want is direct, overhead or reflected light that creates glare. Giving workers personal control of their light is also very important but only if the person is controlling their own personal lighting zone.”
In 2003, the consortium wrote, “People who are more satisfied with their lighting rate the space as more attractive, are happier, and are more comfortable and satisfied with their environment and their work.” In its investigation, six lighting conditions were provided and rated by comfort level. The most preferred design (rated as comfortable by 91 percent) provided direct/indirect lighting, wall washing and occupant dimming control of the overhead lighting supplied for workstations. Occupants with dimming control were shown to have increased motivation and were able to sustain their “persistence and vigilance” over the workday. Direct/indirect lighting represented some light directed downward, toward the work surface, and some light upward, toward the ceiling.
To confirm and delve deeper into those results, the consortium collaborated in 2008–2009 with lighting behaviorist, Jennifer Veitch, Ph.D., senior research officer with the National Research Council of Canada in Ottawa. In the study, occupants with control over their workspace lighting found their moods healthier and felt more engaged in their jobs. This was the first time such linkages had been demonstrated. Individually controlled lighting also reduced lighting energy use by 10 percent.
“The open office plan is the big deal today, as is energy efficiency,” Jones said. “In an effort to decrease energy consumption, a lot of people simply lower lighting or wattage, overall sacrificing lighting quality. You need to give people the light when they need it without sacrifice.”
In Jones’ estimation, the trend in lighting that promotes worker productivity and satisfaction is increasing, and its importance is recognized more.
“We now know good lighting improves day-to-day worker satisfaction. Personal controlled lighting, LEDs and intelligent lighting and controls are all hot right now. Companies like ours are working to develop office lighting products that pay attention to the psychological, energy use and safety needs for good office lighting in an open plan environment,” Jones said.
Where energy efficiency and worker productivity meet
David Cordell, ASID, IIDA, LEED ID+C, and Jon Penndorf, AIA, LEED AP BD+C, wanted to research energy consumption and its effect on behavior within the sustainable open office environment. They didn’t have to look far for funding. Their employer, Perkins+Will, a global architecture and design firm, offers employees in-house microgrants. Cordell and Penndorf took the opportunity to help their new Washington, D.C., office earn LEED Platinum, Commercial Interior status, and to look at the effect of energy-efficiency measures in the workplace.
The D.C. office was conceived to be a sustainability showcase. It purchases all green power. It submeters heating, ventilating, air conditioning, lighting, computer and plug loads to monitor energy consumption. And, through an energy management system, it benchmarks consumption data for itself and many of the firm’s other locations. In lighting alone, it has reduced power usage by an estimated 35 percent through a strategy that uses daylight sensors, occupancy sensors, and LED and fluorescent lighting. The study focused on the open office portion of the work space, about 60 percent. Called “The Living Lab,” they nicknamed the lighting portion of their study “The Lighting Lab.”
“Our office is really designed as a testing ground for new strategies before we recommend them to clients,” Cordell said. “We aren’t lighting designers, but we are end-users.”
Before the study, both men recognized their open office space was overlit.
“We know OSHA, GSA and others have set desired lighting levels on a work surface at 30–40 foot-candles; though the range is 50 for paper-oriented tasks,” Penndorf said. “We were at 200 foot-candles.”
The study largely focused on perceived comfort and its effects on worker productivity. Employees were briefed at what was attempting to be measured, though they didn’t always know when the testing was taking place.
“Ergonomic and productivity goals were judged based on occupant surveys administered anonymously over the course of the study, and by ‘complaint logs’ kept by office administrative staff,” Penndorf said.
“Our building block was a University of Idaho study that showed workers perceived greater productivity in a comfortably lit space,” Cordell said. “We took our lighting control software and tested it in three different ways: task tuning, variable shedding and daylight harvesting. We were trying to find that correct lighting level that is comfortable for everyone.”
They tested over 12 weeks in summer 2012 and repeated in the winter of 2012/2013 to address seasonal variation.
Both men found worker perception of the lighting influenced behavior.
“After we announced a scheduled period of load-shedding, one worker said she had noticed lights going on and off over her workstation,” Cordell said. “That was her perception, as lights were not affected in her work area.”
Cordell and Penndorf determined that load-shedding was best suited for corridor or other support space lighting.
The men balanced and created a pleasing, productive light level throughout the office based on task. They achieved a granular lighting approach (imperceptible dimming for occupants) blended with available light and personal task lighting.
“To get to the optimum foot-candle range, you are minimizing the perceived light changes on occupants,” Cordell said. “Through this task tuning, we achieved a 60 percent energy savings supplementing overhead artificial light with daylighting and individual task lighting. We located meeting spaces along the window perimeters to take full advantage of our daylight harvesting system.”
Work spaces were located based on the type of work being done. To mitigate glare from the windows, automated shades were installed. Those whose job required extensive computer monitor-use had screens positioned appropriately or were located away from windows where possible.
Windows make up the entire eastern facade of the D.C. office. While that has made the office’s daylighting approach quite effective, the facade’s location and lack of obstruction was also key to its success.
“I feel daylighting is critical for modern design energy efficiency and human performance, but it’s not a cure-all, and it can be done poorly,” Penndorf said. “You need to consider building orientation, seasonality and neighboring buildings.”
Successfully creating an effective lighting space that benefits its occupants requires goal-setting, Cordell said. The electrical contractor (EC) can be a partner in achieving those goals.
“If an EC understands what you are trying to accomplish as you build out the space, he can raise a red flag when the design or an installation hinders goals. Bringing ECs into an integrated design team takes advantage of their guidance and expertise, so you can achieve a balance of energy efficiency and high worker productivity.”