Ice Damming Around Skylights - How To Minimize Heat Loss in These Areas
Skylights have often been associated with massive heat loss and inefficiency. However, the area around the skylight is most likely the true culprit. Most builders do not know how to insulate the odd framing around a skylight so there tends to be a lot of energy loss due to insufficient insulation.
The Framed Walls of the Skylite
The walls of a skylight are actually part of the attic space. They are hardly ever treated as such and require attic R-value insulation and air sealing. The best method for insulation and air sealing of the skylight walls is closed cell polyurethane spray foam. This will air seal the wall areas and also allow you to insulate over the studs creating a monolithic thermal blanket. 4 to 5 inches will provide an R-24 to R-30 and prevent the warm air from escaping and melting snow on the roof.
The Flat Attic Areas Around the Skylight
This area is easy to insulate. Blow-in cellulose insulation will prevent the massive thermal loss through the ceiling that is being experienced. This can be accomplished by blowing 12-14 inches (R-40 to R-50) of cellulose insulation.
Proper Waterproofing Around the Skylight
Of course some heat loss is inevitable, so proper waterproofing of the skylight is very important. Ice and water shield 4-6 feet around the skylight will keep water from ice dams or any other moisture form sneaking under the shingles and building paper. The first piece is always installed on the low side of the roof and the top piece goes over the flashing before the shingles are installed.
This project should be professionally performed. If you are not able to inspect the attic area because of lack of acess, it is wise to hire a certified thermographer. A thermographer will use a thermal imaging camera to literally see inside your ceiling and walls. They usually charge $200-$500 for this service and go through the whole house before and after a project is completed.