Home Improvement : Skylights Can Save on Lighting, Heating

QUESTION: I would like to install a skylight in my family room, but I’m concerned that it will waste energy and increase my utility bills. Are there any energy-efficient skylights and how should I select one?

ANSWER: There are some new very energy-efficient skylights available. With proper selection and installation, one can actually lower your utility bills. Installing one is a very simple do-it-yourself weekend job.

Skylights can save energy by reducing the need for electric lights and by solar heat gain in the fall, winter and spring. A typical skylight provides several times more light than a window of the same size. The light also diffuses better throughout your room.

Much of the new super-high-efficiency window glass technology is available in skylights too. Double-pane, low-emissivity-coated (low-E) argon-filled glass and Heat Mirror glass are the most efficient, with insulating R-values of R-4 or greater. The sun’s fading ultraviolet rays are also reduced.

Dome-shaped triple- and double-pane plastic glazing is also efficient and often less expensive. Although the dome shape can slightly distort the light and view, it tends to self-clean when it rains.

For plastic glazing, acrylic maintains its clarity best. Polycarbonate plastic is almost as crystal-clear as acrylic and is virtually unbreakable.

For solar heat gain from a south- or west-facing skylight, clear high- efficiency glass is best. A location above a dark ceramic tile floor or a brick wall is excellent to absorb the solar heat. However, during the summer, you should provide some type of shading to reduce overheating.

For general room lighting only, a bronze or smoke tinted skylight is best. It still provides plenty of light during the day and it reduces the heat buildup in the summer. Clear is best for north-facing locations.

At night during the winter, using an insulated cover reduces the heat loss. I use a 2-inch-thick piece of rigid foam insulation under my low-E argon- filled skylight. Cut it slightly smaller than the opening and put foam weatherstripping around the outside edge. The weatherstripping seals and holds up the lightweight insulating foam cover in the skylight opening.

The skylight frame and curb (the raised section it sets on) should be made of an insulating material--vinyl, fiberglass, polycarbonate--or have a thermal break if it is aluminum. Some very-high-efficiency ones use rigid insulating foam in the frame itself.

You can write to me for Utility Bills Update No. 351 showing a buyer’s guide of super-high-efficiency-skylight manufacturers, types of glazing and frame materials offered, and do-it-yourself installation instructions. Please include $1 and a self-addressed business-sized envelope. Send your requests to James Dulley, c/o Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.