Skylight Information 5 - Skylight Installation Tips

Even the most energy-efficient skylight must be properly installed to ensure that its energy performance is achieved. Therefore, it's best to have a professional install your skylight.

In addition to following the manufacturer's guidelines when installing a skylight, it's also important to consider slope and moisture control.

Slope The slope or tilt of the skylight affects solar heat gain. A low-slope will admit relatively more solar heat in the summer and less in the winter, exactly the opposite of what is desirable.

As a general rule of thumb, you want to achieve a slope equal to your geographical latitude plus 5 to 15 degrees. For example, the optimum slope for a south-facing skylight in Columbus, Ohio, at 40º North latitude, is 45º to 55º. At least one skylight manufacturer makes a prefabricated, tilted base that increases the angle of a skylight above the roof.

Moisture Control Water leaks are a common problem with skylights. Take the following steps to avoid water leaks:

  • Mount the skylight above the roof surface
  • Install a curb (a raised, watertight lip that helps to deflect water away from the skylight) and flashing
  • Thoroughly seal joints
  • Follow the manufacturer's guidelines.

It is also prudent to apply a layer of sheet waterproofing over the flanges/flashing of the skylight. This is generally installed under the finish roofing material as an aid in protecting against ice dams. Avoid water diversion devices such as roof crickets or diverter strips, as they often create more problems than they solve.

Courtesy of the U.S. Department of Energy