Some persuasive research over the past decade shows a strong relationship between the availability of daylight in classrooms and increased test scores for students. Schools seeking to apply that research to actual school construction projects face several hurdles, but the benefits can be real and long-lasting.
When schools and universities combine that educational benefit with the energy savings that can accrue, the only appropriate question to ask is “How do we do it?”
Benefits in the classroom
Heschong Mahone Group's “Daylighting in Schools: Reanalysis Report,” which was published in October 2003 and funded by the California Energy Commission, expanded and validated previous research the group had done. In the original report and in the re-analysis, the group found a statistical correlation between the amount of certain types of daylight in elementary school classrooms and student performance.
The research indicated that “students in classrooms with the most daylight showed a 21 percent improvement in learning rates compared (with) students in classrooms with the least daylight.” The study also confirmed that the effect of daylighting did not vary by grade or the physical characteristics of the classrooms.
The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute in Troy, N.Y., has published a number of Delta Portfolio case studies that address lighting in schools and adds another dimension to the value of good daylighting design. Reference is repeatedly made to shades being drawn to keep out direct sunlight.
However, good architectural daylighting design would address that problem before it got to the plane of the shade. Exterior shading devices enable reflected and diffuse daylight to be admitted without direct sunlight. The application of this technique admits daylight in quantities that are comfortable and creates fewer reflection problems for computer screens. These methods add first-cost to projects, but the LRC reports provide projected savings for the schools if lights are turned off in response to daylight availability.
In addition to the education and energy benefits, the ability of the schools to use energy-saving building methods as a tool for teaching principles of sustainability is a real plus.
Make it work
Among the important aspects of using daylight effectively in classrooms are designing buildings and rooms so daylight can be admitted without glare; maintaining views under most, if not all, conditions; and ensuring that audiovisual and teaching-wall requirements can be met. In order to save energy, efficient electric lighting layouts and control strategies must be incorporated into the electrical design.
Architecturally, the preferred arrangement is to use view glazing that is separate from the daylight-admitting apertures. This enables different shading strategies to be used. Often, sun-shading louvers and light shelves are used to admit reflected daylight and maintain views without admitting direct sun.
Classroom organization is best with the teaching wall perpendicular to the window wall. Daylight can illuminate the desks and teaching wall without causing glare. A bright wall of glazing reflected off a glossy whiteboard or bleeding out a projection screen that is parallel to the glazing is unworkable for a classroom and will cause the shades to be closed. The side-lighted room offers students the benefit of feeling the effect of the daylight off to the side, while limiting the distraction.
The Lighting Research Center's Delta Portfolio publications stress the suitability of indirect lighting for classrooms. Distributing lights evenly around the room surfaces provides the most comfortable visual environment, and it mixes well with daylight. Often, there is a direct component to the fixture that can be isolated. This provides the advantage of eliminating the indirect light when there is a projected image on a screen that needs to be seen in detail.
These direct/indirect fixtures are situated best perpendicular to the daylight apertures and parallel to the teaching wall. The length of each fixture should respond to the “daylight zone,” which is the area of the classroom within about 15 feet of the window. That area will have enough daylight under normal conditions to allow the electric lights to be turned off or dimmed and still maintain the required light level at desktop. Lighting control zones then can be organized to respond to both daylight availability and projection screen use.
Flipping a switch
The architectural skin design and classroom layout organization provide benefits to learning. The electric lighting controls provide energy cost savings. If automatic daylighting controls are not included in the project, a school is unlikely to see optimum savings. Dedicated staff will use wall switches to turn off lights, but too often, the switches go unused and the lights stay on unnecessarily.
Automatic lighting controls can take one of two approaches to turning off the lights. They can be multi-level switched or continuously dimmed. With the switched system, one row of lamps in a row of fixtures is switched separately from the other row so that lights can be all on, half on or all off. Additional levels can be achieved with either more lamps in the fixtures or more divisions along the length of the row. With the continuously dimmed system, all the lamps are dimmed as daylight becomes more available until a minimum level is achieved, and then they are switched off.
The switched systems tend to be more distracting because of the jumps in light level as the lamps are turned on and off. They may be found in schools where budgets are limited because of the impression that this system costs less than the dimmed system. However, this no longer is entirely true.
A dimming system is ideal for classrooms because the dimming takes place seamlessly and goes undetected by students. Although dimming ballasts are more expensive than normal ballasts, fewer pieces of equipment are required for the dimmed system, so installation costs can be lower than with the switched systems. In order to achieve this savings, the contractors and their electricians must be knowledgeable about the equipment and proper installation techniques.
The simplest daylight dimming system is a photocell that “reads” how much daylight is present and sends a signal to the ballasts to dim or increase output. A simple switch on the wall turns the fixtures on and off, and everything else is automatic. More sophisticated systems provide additional flexibility and often add the ability to have single-button access to a group of preset scenes such as lecture, video and group tasks.
A properly installed, calibrated and commissioned lighting system will save a substantial amount of energy in a classroom that is in continuous use throughout the day. Local energy costs will affect what that savings is and how quickly the investment will be paid back. Poorly installed and maintained systems will cause distractions that will degrade the learning environment, and give students and teachers a bad impression of the technology.
Frazier, IALD, LC, LEED AP, is principal at Candela Lighting Design and Consulting, Seattle. She has more than 22 years of experience as an independent lighting designer and instructor.
Number of feet from the window that encompasses the “daylight zone.”