Skylights can add a lot to a home. First of all, they can give it a bright, open natural feel, plus ventilation. Typically, a skylight will give you about five times as much light as a window of the same size. It will also spread that light more evenly throughout a room, rather than concentrating it near the outside walls. And, unlike windows, skylights don't steal wall space. This gives you greater freedom to arrange your furniture.

No wonder the skylight is the second most popular option on new homes and home improvements.

But despite this popularity, few homeowners know anything about buying skylights. Let's see what we can do to solve this problem. ENERGY EFFICIENCY. Just a few years ago, skylights were clearly energy-wasters. Today, however, new designs have made skylights net energy-savers.

One type of energy-efficient design is designed to cut heat losses through both the glazing, and through the aluminum frame, normally a tremendous waster of heat.

Heat loss through the glazing is cut roughly in half, simply by using a double dome. Experts recommend double-glazed skylights for most of the U.S. If you live in a southern area (with less than 2,500 annual heating degree days) single glazing is more cost-effective. And if you live in a very cold climate (over 7,500 degree days), triple glazing is best.

Losses through the aluminum frame are reduced by means of a "thermal break," a rubber or plastic extrusion that isolates the inside of the frame from the outside so that heat can't flow directly through the highly conductive aluminum.

Another way to achieve the same thing is to use plastic instead of aluminum for the frame. Either way, you cut down on the flow of heat out through the frame. This in turn keeps in the interior surfaces of the frame warm, and helps cut down on condensation.

Condensation can be a real problem in cold weather. As water collects on skylight and frame, it can drop down, damaging or staining the gypsum around the skylight. And that brings us to another energy-saving feature.

In the past, most skylights handled the problem of condensation by catching the water in a trough in the frame, and then bleeding the water through weep holes onto the roof. This works, but the weep holes are an easy exit for heat as well as water. Some of the new designs solve this problem by incorporating an oversize condensation trough. The trough is big enough to hold all the condensation until it has a chance to evaporate. This allows the elimination of the weep holes, and a tremendous reduction in heat loss. SIZE. The size of a skylight determines how much light it will give you. For the average room, pick a size that has an area roughly equal to one twenty-third the area of that room. You can increase this if you want more light (for an activity room or plant) or decrease it if you want less light (in a bedroom, for example). Ceiling height also affects skylight size. High ceilings require larger skylights to compensate for light fall-off. COLORS. Clear skylights let in the most light, but the light is contrasty and concentrated. A translucent white skylights admits about a third less light, but softens and distributes it better than a clear skylight. Bronze and gray tints are popular in the South and Southwest because they can cut down on solar heat gain, and keep a house cooler in the summer. CONSTRUCTION. The cheapest skylights have no frame at all; they mount right on your roof. Many of these are made with cheap plastics that discolor and become brittle with age. Best bet is to stay from this type in favor of those that come with frames. These are usually better made, and offer greater protection against condensation. Though they cost more, they are worth it.