Vapor Barriers/Retarders
Installing a vapor barrier or retarder is an essential step in every thermal insulation project.
A vapor barrier or retarder is vital component of exterior walls. It controls vapor transmission and helps prevent condensation from forming inside the walls and ceilings of your home. Vapor barriers/retarders are particularly important in Canada, and in US states that experience winter temperatures below freezing.
As illustrated in the diagram, warm air inside your home has a higher pressure than the cold air outside. It also contains moisture. To equalize the difference in pressure, the warm air tries to escape through your walls. The vapor barrier or retarder is what prevents that from happening. Without it, the escaping warm, humid air would pass through the insulation and contact the cold outer wall surface, where it would condense and collect. The resulting build-up of water inside the walls has the potential to damage wall framing members and promote the development of mold.
Consult your local authority having jurisdiction on the proper location and installation for the vapor barrier/retarder.
While many professional contractors feel that polyethylene is the best choice, you should always consult your local building code when you’re doing the work yourself.
Vapor barriers/retarders are not required when you are soundproofing interior walls and ceilings with Roxul Safe'n'Sound. However, insulation should not be left exposed. Drywall is the recommended wall covering.
