In the 21st century, educators and school facility designers have come to embrace daylighting strategies as a way to deliver instructional spaces that not only use energy more efficiently but also help students perform better academically.
So if daylight is good, more daylight is better, right? Well, if an unplanned nap ever turned your short sunbathing session into a lobster-red blisterfest, you know that more sun isn’t necessarily better.
Too much light, especially direct rays that create glare, can be distracting to students and bring unwanted solar heat to a learning space.
“Location of windows in a building must be designed in such a way as to avoid the admittance of direct sun on task surfaces or into occupants’ eyes,” says the National Institute of Building Science’s Whole Building Design Guide.
“The aim of an efficient daylighting design is not only to provide illuminance levels that are sufficient for good performance, but also to maintain a comfortable and pleasing atmosphere,” the guide states. “Glare, or excessive brightness contrast within the field of view, is an aspect of lighting that can cause discomfort to occupants.”
The seminal study that accelerated the impetus for maximizing natural light in schools, a 1999 report from the Heschong Mahone Group, found that students in classrooms with greater amounts of daylight scored better in math and reading tests.
But in that study and a 2003 follow-up, researchers also found that sources of glare in a classroom negatively affected student performance.
“This is especially true for math learning, where instruction is often visually demonstrated on the front teaching wall,” the 2003 study said. “…Direct sun penetration into classrooms, especially through unshaded east- or south-facing windows, is associated with negative student performance, likely causing both glare and thermal discomfort.”
Block that beam
Window placement and sizing, the type of glazing selected, building and classroom orientation, structural elements of a facility, the reflectance levels of materials and surfaces, and the types of shading devices in place are some of the ways that school spaces can enhance the benefits of daylighting and avoid the problems that glare may create.
“More windows do not automatically result in more daylighting,” the Whole Building Design Guide cautions. “Natural light has to be controlled and distributed properly throughout the workspace.”
The Design Guide for Daylighting Schools was put together by Innovative Design, an architectural firm, for Daylight Dividends, a program of the Lighting Research Center at the Rensselaer Polytechnic Institute in Troy, N.Y. It offers numerous suggestions for eliminating glare and avoiding the unwanted effects of direct sunlight in instructional spaces and other areas of an education facility.
Incorporating roof monitors and light shelves into a school facility design should be at the top of the list for daylighting strategies, the guide says.
For single-story schools, roof monitors with south-facing glazing, properly sized overhangs and interior baffles to diffuse the sunlight entering the space helps create uniform illumination throughout a space, enables daylight to reach spaces far from the perimeter of the building, and eliminates contrast and glare.
The baffles should hang parallel to the glazing and be spaced so that they block views of the sky from all points of the room and prevent direct sunrays from entering the space. Light-colored, translucent baffles will reflect the sunlight and help eliminate contrast from one side of the baffle to the other, the guide says.
The downside of roof monitors is that they can be used only in one-story buildings.
A light shelf, on the other hand, will work in a multi-story facility. It is a horizontal building element installed above eye level, and reflects daylight deep into a space. Light shelves enhance daylighting by bouncing the sun’s rays to the back reaches of classrooms and help shade the glazing that sits below the light shelves.
Made in the shade
But, the guide notes, a light shelf will not stop all direct sunlight from entering a space through windows. It recommends installing directional blinds to reflect that light to the ceiling or toward the walls. Vertical blinds also can be used to bounce sunlight outward.
If vertical blinds are installed on a window, there should be separate blinds for the area above a light shelf and the area below. Having one blind for the entire window, the guide says, will diminish the reflective benefits of the light shelf.
The color of the ceiling, walls, floor and furniture also will affect the amount of glare in an instructional space and whether daylighting strategies will succeed.
“When considering finish surfaces, install light colors (white is best) to ensure that the daylight is reflected throughout the space,” the guide says. “In order of importance, the lightest colors should be installed at the skywell, ceiling, wall, furniture and floor.”
In assessing the effects of glare in a school facility, school planners should recognize what might be acceptable conditions for some students will be too distracting and uncomfortable for others.
“The lighting expectations and glare tolerance of building occupants can vary greatly,” the Whole Building Design Guide says. “If possible, provide flexibility in the furniture system and programming to allow for variability in occupant tolerance and illumination requirements.”