The appropriate use of daylight in educational environments has myriad benefits: healthier students and fewer sick days, as well as improved moods, learning aptitudes, and attention spans. In the study “Daylight and School Performance in European Schoolchildren,” published in December 2020, researchers found that “classroom characteristics associated with daylighting do significantly impact the performance of the school children and may account for more than 20% of the variation between performance test scores” in math and logic. The window-to-floor area ratio in classrooms seemed to have the most significant effect, with larger window areas being more desirable.
However, the study emphasized the importance of controlling the amount of incoming daylight, through window shades for example. Stantec has reached similar conclusions through its studies. Since 2012, the global firm’s Research + Benchmarking group has conducted post-occupancy studies in Texas schools designed by itself as well as by other firms. The feedback it has received includes, perhaps surprisingly, dissatisfaction with daylight.
Shivani Langer, AIA, a principal, senior project architect, and regional sustainability leader based in Stantec’s Austin, Texas, office, expounded on these findings in her 2019 article “Education design: How much daylight is right for today’s tech-enabled schools?” Two of the 10 schools surveyed had wall-to-wall glazing, but Stantec’s research group found that even with sunshades and light shelves, user satisfaction with the daylight was very low—even lower than for the traditional classroom layout with two windows at each corner of the room. “The major source of dissatisfaction was glare and the inability of the students to see notes on the marker board or projections on the screen in their classrooms,” Langer says.
After studying a variety of window sizes and configurations in typical classroom settings in Houston, she and her team discovered that window size is not directly proportional to the amount of useful light available in a space. In fact, the amount of useful daylight illuminance (UDI)—a metric that references when illuminance is supplied by daylight alone—is actually lower in the case of larger windows. “Designing big windows doesn’t necessarily mean adding quality daylight in a space,” Shivani says. “Because glare is not considered useful, the amount of useful daylight available from a space with a 28% window-to-wall ratio may be higher than one with 52%.”