What Is It and How Does It Work?
Daylighting is the use of natural light through windows and skylights to provide lighting for your home. Well-controlled daylight apertures can make for a more pleasant interior environment and reduce the need for electric lighting, which can help you to save money on your electric bills. Also, recent studies have indicated that natural light can have positive effects on worker productivity and overall health. The daylighting strategies that work best for your home will depend on your climate and the orientation of your home.
When considering the placement of windows, it is important to make a distinction between “daylight” and “sunlight.” Direct sunlight can often cause a distracting glare, whereas daylight should provide less dramatic contrast. Including sunshades and minimizing the amount of windows to the east and west—where it is difficult to shade the rising and setting sun when it is low in the sky—can help reduce glare from direct sunlight.
Another seemingly obvious, but still critical, consideration is to include accessible controls on electrical lights. After all, it is not adequate daylighting that will reduce your energy bills, but turning off or dimming your electric lights. Interior finishings can have an effect on daylighting as well. If the color of your walls, ceiling, and floor is very dark, the impact of daylighting will not be as noticeable. Light-colored surfaces will help to increase the impact of daylighting.
Why Should I Consider It?
Effective daylighting strategies help to reduce dependence on electric lighting, which can lower your electricity bills in a few different ways. First, when you take advantage of free lighting from the sun, you do not need to turn on as many electric lights. Also, since electric lights create heat, added daylighting will reduce your cooling load. A reduced cooling load means that you can install a smaller air-conditioning system and will not need to run the AC as often during the summer. In fact, a comprehensive lighting strategy that emphasizes daylighting can reduce energy loads by a minimum of 25 percent and up to 90 percent in some cases.
What Are the Options?
If you are considering a daylighting strategy in new construction or a substantial renovation, there are a few factors that you should focus on.
Daylight zoning is the concept that certain rooms and spaces should have access to more daylight than others. Rooms in which tasks demand a lot of light need more daylight. For example, you will most likely want more daylight in an office or living room than in a hallway. Service spaces, such as closets and bathrooms, may not need any daylight at all.
Toplighting is the use of skylights, saw-tooth roofs, and clerestory windows high up on walls to bring daylight into a building. Toplighting can be a useful strategy because it can bring in consistent daylight and make direct sunlight easy to control, reducing glare.
Sidelighting is the familiar use of the wall plane to introduce daylighting into a building through windows. The benefit of this strategy is its versatility. Windows can also be used to provide views, ventilation, and passive solar heating in the winter. They also must include shading controls to prevent unwanted heat gain during warm days.
Shading devices are important tools in preventing direct sunlight from causing glare and overheating during the summer. The shading devices that you consider as part of your daylighting strategy are also used in a passive solar heating strategy. During the winter when sun angles are low, you will want some direct sunlight to enter your home to provide warmth. Shading devices can allow the sun's rays to warm your home during the winter, while preventing higher summer sun angles from providing too much heat gain.
What Are the Potential Benefits?
Daylighting has also been shown to have a beneficial impact on health and productivity. Multiple studies in recent years have shown that people who live and work in spaces that are naturally lit and have views to the outside are healthier and perform better at work.
How Much Does It Cost?
In many cases, you can integrate a daylighting strategy into new construction for no extra cost. Daylighting is not so much about how many windows you have, as it is about where they are located. If you have an existing home and are interested in considering daylighting strategies, your options will be more limited. However, if you have plenty of windows with adequate controls to prevent glare and unwanted heat gain, you may be able to reduce your reliance on electric lighting.
Additionally, by integrating a well-designed daylighting strategy into a new home, you will also decrease the cooling load, which will allow you to downsize your cooling system.
What Else Should I Know?
South-facing windows are very good apertures for providing daylighting as well as controlling summer heat gain. North-facing windows are also useful for daylighting since they provide very even light, no glare, and no summer heat gain. In very cold climates, however, north-facing windows may cause too much heat loss. East- and west-facing windows are problematic for daylighting. Morning and evening sun angles are very low and difficult to shade, so a house with a lot of east- and west-facing windows is at risk for unwanted heat gain in the summer, with little added benefit to passive solar heating in the winter.