SKYLIGHTS IN RAINY, COLD CLIMATES

Curb mounted skylights are often the best solution in rainy-snowy climates. The curb will raise the base of the skylight above the roof level, allowing increased protection against water and ice. The height of the curb will dependent on the slope of the roof: the flatter the roof, the higher should be the curb….

Ice damming

Skylights can cause ice damming due to the heat losses they may propitiate. These losses cause snow melting that often refreezes downstream, with the subsequent ice damming and possible water penetration below the shingles and leakage. Underlayment is crucial to prevent water leakage and ice damming.

Underlayment

Roofing underlayment consists in most cases on a self-sealing rubberized asphalt sheet, and is especially important in regions with extreme weather conditions. Roofing paper about 8 inches wide is also largely used.

Insulation

Proper interior insulation of the skylight surroundings is also important to prevent ice damming. Its goal is to reduce heat loss and the consequent snow melt and ice damming. That insulation should have a thermal resistance equivalent or superior to the thermal resistance of the neighboring roof and exterior walls.

Skylight position

To avoid snow accumulation, skylights should be positioned away from walls, chimneys, and other roof protrusions.

Step flashing

Step flashing and counter flashing are particularly important in rainy climates.

See: Rectangular Skylights flashing

Saddle

Installing a saddle above the skylight, on the upper part of the roof, is important and recommended to divert water around the skylight structures and namely to divert it from its head. Saddles add further protection against water penetration and ice damming.