Should Skylight Wells Be Insulated?

Well Insulation

• Skylight window wells are insulated to the same level as any other part of your roof. Most homes in the United States require insulation with an R-value between R-30 and R-38. This rating determines how effective your insulation prevents heat loss through convection. Most types of batt and loose-fill insulation require between 10 and 14 inches of insulation to provide an adequate level of resistance to changes in temperature. If the space in your attic around the skylight well does not provide enough space to install the necessary amount of insulation, you can use rigid foam board insulation instead. Make sure that the insulation around the skylight well has no gaps and covers the wood or metal framing of the skylight well.

Window Sealing

• Properly sealing the skylight into the frame above the skylight well ensures that air will not leak into the space around the well. A properly sealed skylight also protects the skylight well from water damage. You can ensure that your skylight is properly sealed with a combination of silicone caulking, metal flashing and construction tape where the window meets the skylight well.

Ventilation

• The shape of your skylight well determines the amount of air circulation around your skylight. During cold weather, the warm moist air in your home can condense on the cold surface of the skylight window. Skylights with a well that extends for more than a foot are particularly subject to this problem. You can alleviate this problem during construction with a flared well design that angles the walls of the skylight well away from the area below the skylight window. This will prevent water from accumulating on your skylight and help limit moisture damage to the drywall and insulation in your skylight well.

Issues

• Installing a vapor barrier between the insulation and the drywall in the skylight well helps protect your insulation against water damage resulting from condensation. If your skylight is designed to open, you will need to check the seals around it annually to ensure that it is not leaking air or moisture into your home. In skylight wells with a narrow opening, installing a sealed barrier across the opening of the skylight well separates the moist air of your home from the skylight window. This barrier can use plexiglass or a layer of transparent window film to prevent warm interior air from condensing against a cold skylight.