Providing light for the workplace has always been at the top of the list for those who build and manage offices. However, they have tended to focus on the effects lighting has on a building’s performance, often at the expense of the people who work there. The cause of this focus has been the rising costs of real estate and energy.

Arguing for a human-centered approach to lighting, one noted expert says that “occupancy quality must take precedence over energy use and sustainability. These now lead. It’s time to switch the focus to people and their task performance.”¹

While people prefer natural light, their workplaces, for obvious practical reasons, are lit by some combination of daylighting (perhaps with views to the outside) and artificial lighting. Within that range of illumination, people have clear preferences for how much and what kind of light they want.

The fact that preferences vary—among people and for the same person at various times during the day—argues for giving them some control. Whatever else people say about office lighting, they make it clear they want the ability to adjust it themselves. And they will adjust it quite differently based on the quality and visual performance of local lighting, ambient lighting, and daylighting.

Giving people control over their lighting helps them feel more satisfied with their workplace. It affects their performance, too, helping them stay engaged in tasks longer and to avoid fatigue. And, lighting that is appropriate for the individual can also increase energy savings if adjustability is part of the picture.

The individual’s right to light

Anyone who has worked in a windowless office lit by fluorescent lights knows something people often take for granted—their affinity for natural light. The strength of that attraction has fueled the trend toward opening up the office with windows and skylights.

The push began in 1975 with the Workplace Ordinance in Germany. It, in turn, influenced the 1989 European Union directive that “workplaces must as far as possible receive sufficient natural light and be equipped with artificial lighting adequate for the protection of workers’ safety and health.” Recent laws in Denmark, perhaps the most stringent in Europe, require that all workplaces have access to daylight.²

In other areas, accreditation programs are taking the place of legislation. These include the Building Research Establishment Environmental Assessment Model (BREEAM) in the U.K., the Green Building Challenge (a collaboration of 20 countries committed to developing a global standard for environmental assessment),³ and the Leadership in Energy and Environmental Design (LEED) system in the U.S.

All of these programs, however, only touch on natural lighting. For example, of the 57 available credits under the LEED program, one credit can be obtained by ensuring a minimum of 2 percent daylight factor over 75 percent of the floor space, and another credit by providing a direct line of sight to windows from 90 percent of the floor space.

The role of natural light in the workplace can also relate to business objectives. One pilot study conducted during the winter months found that office workers assigned to interior or windowed offices both occupied their workstation about the same amount of time. However, those with “windowed offices spent more time on computer tasks and less time talking on the telephone and to coworkers than matched workers in interior offices. The root cause of these findings remains unknown,but the results are consistent with the hypothesis that bright light during the day improves productivity during winter months.”⁴

In addition to the positive effects of daylighting, it has a clear range of negative effects related to:

• Luminance ratios of daylighting to the task
• Visual adaptation problems from reduced ability to see the task in the presence of bright daylighting
• Increased stress on the older worker because of uncontrolled daylighting

The tendency toward floor-to-ceiling glazed architecture combined with the desire for simplicity often results in uncontrolled glare, which reduces the ability to work.