Do skylights mean sky-high energy bills?

Well-placed skylights can brighten rooms that lack daylight.

Kitchens and dining rooms cry out for natural light, and lots of folks consider installing skylights to bring that outside world indoors and make their living space a bit more livable.

Consumers should know, however, that skylights, even when installed properly, can impact energy bills and comfort level, so some advance research can pay real dividends.

One downside of skylights is they can add heat to your home during the summer and contribute to heat loss during the winter. The amount of each depends upon a number of elements, including the skylight’s energy rating, size, placement, and quality of installation. You can check its energy efficiency by looking at the skylight’s NFRC Energy Performance Label, which shows the four pieces of the energy efficiency puzzle: insulation value (U-factor), ability to transmit solar heat (solar heat gain coefficient), ability to allow light to transfer (visible transmittance), and air leakage.

Finding a unit with the best ratings in all these categories will help maximize your skylight’s energy efficiency and performance. It’s probably worth spending a little more on a better product, since professional installation takes up the lion’s share of the cost of installing a skylight into an existing roof.

Just as important as finding the right skylight is determining the proper size, number, and placement. You want adequate light, but too much can make a room less functional on a bright day. Skylights on a steep, north-facing roof will reduce the unwanted solar heat gain in the summer, but this also reduces the desirable solar heat gain in winter.

Proper installation by a knowledgeable professional is essential to avoid all-too-common problems such as water leaks, air leaks, or inadequate insulation.

An alternative option to the regular skylight is the tubular skylight. A small skylight on the roof is connected to a flexible tube that runs through the attic to a room below. This system provides a diffused natural light. The tube is much smaller than a skylight shaft and is easier and less expensive to install. The tube has less heat loss and is less leak-prone. Tubular skylights can fit into spaces that a traditional skylight can’t, and they can be a better choice in rooms with high moisture, like bathrooms, saunas, or indoor swimming pools.

More of Patrick Keegan’s energy efficiency advice is available
at his website.