Q: In one of your recent columns you concluded an answer on lighting a room by stating, "You also may wish to consider a skylight or two. With the proper roof configuration and right exposure, a skylight can be a real winner." What is a proper roof configuration and exposure? - Jackie H.

A: There are a number of elements that influence how effective a skylight can be. One of the most important elements is the configuration of the roof. That includes how the roof is framed (stick or truss), its pitch (the rise-to-run ratio) and the style of the roof (gable, hip, etc.).For example, you may wish to install a skylight in your bathroom where no window exists. However, upon investigating the roof you find the surface is formed by two planes that meet at an angle to form a trough, which makes it virtually impossible to install a skylight in that location.

The same is true where a proposed skylight may come into play with a hip or the ridge of the roof, although some major manufacturers of skylights have begun to produce skylights specifically designed for installation at the ridge.

Another example would be the installation of a skylight in a high-pitched roof. More often than not this would involve the construction of a long tunnel-like chase between the ceiling and the roof. Although you would gain some light, you may find that it is significantly less then what you expected due to the long chase. This condition is especially true of interior halls at the center of the home, where the roof is often the highest.

If you live in a home where the roof framing system consists of manufactured trusses, the size and shape of your skylight is typically dictated by the configuration of the trusses. This is because most building officials will not allow existing roof trusses to be cut or altered without very specific engineering. This could tend to make what started out to be a simple skylight installation a very costly undertaking.

Finally, be conscious of exposure when considering the placement of a skylight: A skylight may sound like a terrific solution to that dark kitchen until you discover that it faces south. You may be trading dark space for hot space.

All things considered, if the only place for the proposed skylight is on the hot side of the house, then we suggest you take a good look at the available energy-efficient units that are insulated, gas-filled, tinted and even-ventilating. Most important of all, that house plant that has been suffering in your dark bathroom will love you forever.

Q: Recently a reader asked how to choose the best new appliances when remodeling. You mentioned a number of factors, such as price and warranty.

Another aspect of an appliance that can affect its "real" cost is energy efficiency. The refrigerator, for example, is responsible for a large percentage of a home's energy use; often significant savings can be achieved by selecting an efficient model.

To choose the most energy-efficient appliance, consumers can consult the yellow "Energy Guide" labels required by law. In addition, the American Council for an Energy-Efficient Economy produces "The Most Energy-Efficient Appliances," a booklet that lists the most efficient models of refrigerators, hot water heaters and other appliances. It is available for $3 from: ACEEE, 1001 Connecticut Ave, Suite 535, Washington, D.C., 10023.