How Energy Efficient Are Skylights Really?


Love the sun and warmth that skylights provide, but wonder what part they play in an energy efficient home?

Skylights can provide you with some energy saving benefits, but there are many things to consider in avoiding some common skylight slip-ups.

Skylights allow sunlight into our living spaces from above without compromising privacy. In delivering abundant daylighting, skylights can reduce energy consumption used for lighting, particularly in interior rooms that do not have direct access to exterior windows.

So, which features should you look for to enjoy the benefits and minimize any negative side effects that skylights can have? Consider the following when evaluating skylights to ensure that they are a bright feature in your home.

Skylight Types

There are three main types of skylights out there. The first is the ventilating skylight, which can be opened by a hand crank. They are typical in kitchens and bathrooms where ventilation is desired. Since hot air rises, ventilating skylights can provide passive cooling to a room in the summer.

A fixed skylight does not open. It is used to provide light but is unable to provide ventilation.

Lastly, a tubular skylight allows light to enter the space, but reduces heat loss and excessive heat gain from the sun because the area of skylight is typically only 10 to 14 inches in diameter.


Locating skylights on the south-facing roof of your home will ensure year-round warmth and sunlight since the sun hits the southern roof during most parts of the year (true for the northern hemisphere). However, in warmer climates where heat gain is a concern, locating the skylight on the north-facing roof will allow the daylighting benefit, yet reduce the solar heat gain and subsequent cooling need of the home.

Water leakage can pose a problem with skylights. After all, they are, essentially, a hole in the roof. Careful installation is key to mitigating water leaks; the U.S. Department of Energy recommends installing the skylight just above the surface of your roof, install a curb and flashing, and tightly seal joints to avoid a leaky ceiling.

Energy Performance

The energy performance of a skylight is another factor that should be considered. While plastic glazing and single-pane glass skylights are common, they perform poorly when it comes to energy performance. Instead, look for skylights with a type of solar heat control glazing; the three most common types are heat-absorption tints, insulating glazing, and low-e coatings.

Heat-absorption tints reduce`solar heat gain and glare depending on the tint color used. Insulating glazing means that the skylight is made of two or more panes of glass, which provides insulation and reduces thermal transfer (i.e. heat gain or loss). Skylights with a low-emissivity (low-e) coating best controls the solar heat transfer into and out of the skylight. And, while they can cost more than the alternatives, they’ll conserve the most amount of energy and save you money on heating and cooling. To learn more about the energy performance of skylights, visit the U.S. Department of Energy.


According to the U.S. Department of Energy, skylights should cover only 5% to 15% of floor area in a room depending on the number of windows in the space. Where day lighting is beneficial, but heat is not, a tubular skylight usually solves the problem. This type of skylight avoids the need for a large surface area (which can result in heat transfer) and, instead, uses a mirror to direct sunlight into the room below.

Now You Know

Now that you know the different types of skylights and the importance of position, size and energy performance, you can select the type and features most appropriate you’re your home to make skylights a functional component of your home’s energy performance.


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