Since the oil crunch of the 1970s, architects, engineers, and homeowners have sought new ways to reduce America’s reliance on traditional energy sources for heating and lighting homes. Certainly one of the most popular and promising answers to emerge has been solar energy. “Although nobody has officially counted, we project there are well over half a million passive solar houses in the United States,” says a spokesperson for the Passive Solar Industries Council.
There are experts who specialize in daylighting design for new construction, but many daylighting techniques can be used in existing homes, as well. Even homes in regions with predominantly overcast days can benefit, as daylight on such days still offers adequate illumination and, often, more-diffuse and even light than brilliantly sunny days. Along with the solar-heating movement, a less known but highly regarded design science has stepped to the fore— “daylighting,” the use of natural light to illuminate the interiors of structures. Of course, this concept is as old as the window itself, but relatively recent advances in lighting research, window and glazing technology, and lighting controls have opened up new horizons for daylighting.
Homeowners love the qualities of natural light, as evidenced by the billions of dollars spent each year on remodeling, often in an effort to achieve more light and greater sense of space. But while homeowners can enjoy and benefit from more natural light by taking advantage of selective daylighting principles and materials, comprehensive daylighting systems don’t make sense for most homes.
For one thing, the potential energy savings are not the same as for commercial and institutional buildings. Though houses do use plenty of electricity for lighting, high-wattage electrical appliances and heating are what gobble up the lion’s share of a home’s power needs. In addition, unlike an office or library, many homes are relatively unoccupied during daylight hours, which shifts a larger percentage of electrical usage to the evenings.
The need for control is different, too. At home, it’s easy to flip off the lights when they’re not needed. Sophisticated controls that automatically raise and lower indoor artificial light levels according to daylight are not necessary.
Providing natural light in houses is often fundamental to their design. As Russell Leslie and Kathryn Conway point out in “The Lighting Pattern Book for Homes,” published by Rensselaer’s Lighting Research Center, “Homes often have generous amounts of daylight, and residential building codes require that most rooms have windows. Typical residential rooms are small enough so that daylight can reach deep into the room, particularly if windows are located high on the wall.”
Adding windows for more light is a somewhat obvious solution, although this could be pricy. Clerestory windows, located on the upper part of a wall, can bounce natural light off the ceiling, increasing illumination. Skylights are another good option, particularly in halls or other enclosed spaces that have few, if any, windows.
Discuss with a professional window contractor whether the costs of new window installation justify the potential energy savings. Do be aware that too much sunlight can cause glare, making people close blinds and turn on lights—the opposite of the goal they were trying to achieve.To direct light coming through windows, use louvers or operable blinds. Another option is to install a “light shelf”—a horizontal, light-colored or metal shelf set across a window to ricochet light off the ceiling and back into the room. This shelf is normally located about 12 inches from the top of the window for a standard 8-foot ceiling.
Using light-colored paint is another way to enhance the reflection of natural light in a room. Where appropriate, you can select paint with a high reflective value.
The bottom line is this: If you’d like to get more natural light into your home, consider some of the basic daylighting materials and techniques available.
Commercial Applications for Daylighting
Because commercial and institutional buildings operate primarily during daylight hours, usually with clearly defined schedules and specific tasks conducted in given areas, these kinds of buildings often lend themselves to comprehensive, systemized daylighting plans. In these buildings, daylighting—the use of natural light to save energy—makes sense.
When a building is flooded with well-controlled natural light, the amount of electricity needed for lighting can plummet. It’s estimated that 25%–40% of a commercial or institutional building’s energy is needed for lighting, often at peak-demand prices; daylighting may save up to 50% of that, depending on how natural light is used.
This is significant, particularly in view of the national energy picture. In the United States, electric lighting consumes about one-fourth of all the energy generated. According to the Rocky Mountain Institute, a nonprofit research and educational organization that fosters efficient use of resources, this usage equals the energy produced by 170 large power plants.
In addition, workers prefer brighter, more naturally lit environments. In fact, a number of studies support the idea that natural light has positive psychological effects on people. They suggest both that our brain perceives the color properties of natural light as “normal” and that we respond in a positive, physical way to its intensity.
The Lighting Research Center at Rensselaer Polytechnic Institute in New York says evidence shows that high light levels can contribute to good health, comfort, and productivity. It also points out that depression caused by seasonal affective disorder (SAD), a sometimes debilitating condition that occurs at high latitudes where people are deprived of sufficient winter daylight, can be successfully treated with high light levels.
