Cold Deck Roof Ventilation

Throughout the balance of this digest the terms attic and roof will and can be used interchangeably.

Cold deck roof ventilation.

Mold on the roof deck or rafters. In a cold climate the primary purpose of ventilation is to maintain a cold roof temperature to avoid ice dams created by melting snow and to vent any moisture that moves from the conditioned living space to the attic. In a cold climate the primary purpose of ventilation is to maintain a cold roof temperature to avoid ice dams created by melting snow and to vent any moisture that moves from the conditioned living space to the attic. This cold deck construction is considered problematic in the humid temperate climate of the uk where the effective ventilation of restricted roof voids may be impractical particularly in sheltered built up areas.

This is caused by air leaking up from your home into the attic in the winter and condensing on the cold deck. The deck air when properly installed with proper exhaust vents provides a balanced ventilation system to rid your attic space of trapped heat and moisture. Ventilation is required to the underside of the deck. Melting snow then backs up behind these dams causing leaks into the roofing material and into the interior of the home.

Ice dams can cause thousands of dollars of damage to roofs and interior building materials. The intent of roof venting varies depending on climate but it is the same if you re venting the entire attic or if you re venting only the roof deck. No ventilation is required for these types of roofs. When placed below the structural deck.

Adding attic ventilation can help but the real problem is heated air leaking up into the attic. Cold deck roof a cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a. In cold climates poor roof ventilation can also cause the buildup of ice on roofs. In cold climates the primary purpose of attic or roof ventilation is to maintain a cold roof temperature to control ice dams created by melting snow and to vent moisture that moves from the conditioned space to the attic ventilation acts to bypass the vapour barrier created by most roof.

See energy smart details in fhb 218 for more on ice dams.