Cold Climate Vent Attic Or Unvented

In colder climates the main purpose of a vented roof is to keep the roof cold and reduce the formation of ice dams.

Cold climate vent attic or unvented.

A secondary goal is to vent moisture that infiltrates the attic from the conditioned home. Basically the term cold roof refers to a traditional roof or vented roof while hot roof refers to a roof that is not ventilated and which has foam insulation attached directly to the roof sheathing. People usually vent attics in cold climates to prevent moisture accumulation in the roof sheathing and control ice dams. Vented roofs vented roofs serve a number of different purposes and their roles vary from climate to climate.

For example if an r 80 unvented cathedralized attic is to be constructed in a cold climate a minimum of r 40 50 should be air impermeable insulation installed and layered according to section r806 5 of the 2012 irc figure 4. Unvented attic construction is most common in housing and type v construction located in the warm climate zones of 1 through 4 but is suitable for any climate zone. With unvented attics the air barrier vapor and thermal controls are installed at the roof deck. In cold northern climates snow can be blown in through these openings accumulating melting and causing damage to the ceiling or creating the potential premature structural failure or mold growth inside the roof assembly.

Durability openings in the soffits gables mushroom and ridge vents allow more than just air to enter the attic. See the irc or the guide unvented attic insulation for details. Unvented attics have higher temperatures on the underside of the roof sheathing. In this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within the building envelope.

Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope. Attic access hatches plumbing chases recessed lights and duct vents all can leak conditioned air making your home less comfortable. Unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. In cold climates moisture in roof assemblies typically comes from inside and the key to problems with moisture is the temperature of the roof sheathing.