The green movement in school design encompasses many techniques to improve the environmental friendliness and energy efficiency of a facility. Some are more complicated than others — probably not many people can explain the intricacies of a geothermal heating system, or the specifics of how solar or wind energy is harnessed. But most people can understand, on some level, the energy-saving benefits of daylighting. They've seen it in their own homes: When the bright sky floods through their windows, they can get by with less artificial lighting.

But to truly tap into all the benefits of daylighting in learning environments, including improved academic performance from students, designers have to use approaches more sophisticated than just adding more and larger windows, and letting the sunlight stream in.

Windows renaissance

The appeal of windows in a classroom and other learning spaces began to lose out in the 1960s to other factors. More schools were being built with air conditioning, and planners concluded that having an abundance of windows would mean the air-conditioning system would run less efficiently. Administrators also were becoming more concerned about campus security, and the more windows a school had, the more opportunity vandals had to damage or break into buildings. Some educators expressed concerns that classroom windows were an invitation to students to let themselves become distracted by what was happening beyond the school walls.

By the 1990s, more school facilities were being constructed, and builders could choose more energy-efficient windows that did not compromise a building's climate-control system. Among designers, a consensus began to grow that daylight once again was considered desirable and beneficial for education spaces.

The study most often cited for jump-starting the embrace of daylighting in school design, a 1999 report from the Heschong Mahone Group, "found a uniformly positive and highly significant correlation between the presence of daylighting and student performance."

Be aware of glare

But the details of the study made it clear that not any kind of daylight would bring about such positive results. Windows and skylights that created glare on walls or desks affected performance negatively.

Regarding classroom skylights, the systems that performed well provided diffuse distribution of daylight by using diffusing lenses or diffusing louvers and wells; prevented direct penetration of sunlight into classrooms; and enabled teachers to directly control the amount of daylight by using louvers or blinds. The systems that did not perform well or had negative effects allowed direct partially diffuse sunlight into classrooms; relied on automatic controls, which were not performing as originally intended; and created small areas of very high daylight illumination.

"It was clear that successful daylighting from windows prevented the penetration of direct sunlight into classrooms," the report says.

The report concluded that designs should incorporate strategies such as light shelves, roof monitors, baffles, louvers and reflective surfaces to spread light throughout a learning space.

"It is critical that in all classrooms, gymnasiums, media centers and administrative spaces, sunlight is either bounced, redirected or filtered so that direct radiation does not enter a part of the room where this could be problematic," says "The Design Guide for Daylighting Schools," created by the architectural firm Innovative Design.