Cold Climate Vent Attic Or Unvented

Attic access hatches plumbing chases recessed lights and duct vents all can leak conditioned air making your home less comfortable.

Cold climate vent attic or unvented.

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. See the irc or the guide unvented attic insulation for details. Unvented attics have higher temperatures on the underside of the roof sheathing.

A secondary goal is to vent moisture that infiltrates the attic from the conditioned home. If the space conditioning system is located in the attic such as it is in warm locations the energy savings that can be realized are very apparent. 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. Durability openings in the soffits gables mushroom and ridge vents allow more than just air to enter the attic.

With unvented attics the air barrier vapor and thermal controls are installed at the roof deck. In colder climates the main purpose of a vented roof is to keep the roof cold and reduce the formation of ice dams. 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. 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.

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 membranes. 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. Vented roofs vented roofs serve a number of different purposes and their roles vary from climate to climate. Wind and air pressure move cold air around chilling homeowners.