Attached garages are popular and common in Canadian houses. Because of the risk of carbon monoxide getting into the house and the likely storage of paints, gasoline and other chemicals in the garage, it must be separated from the house by an effective air barrier system. If there is a connecting door, it must be tightly fitted and weatherstripped and provided with a closure.

Ensure that the ventilation system for the house is isolated from the garage to prevent fumes from entering the living space. Even heated garages are considered by the building code to be unconditioned spaces (when the garage door is open) and therefore any wall or ceiling that separates the garage from living space must be insulated.

Source : Canada Mortgage and Housing Corporation (CMHC)