Vapour Barrier Exterior Wall

To know if you need a vapor retarder ask yourself a few basic questions.

Vapour barrier exterior wall.

A vapour barrier sometimes referred to as vapour retarder is typically a plastic or foil sheet used for damp proofing to prevent interstitial condensation from forming in various building assemblies such as walls roofs foundations and floors. Finished basements often receive a vapor barrier layer between the concrete and the floor treatment to prevent damage from heavy rains or other moisture seepage. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

In any case the vapor barrier must point to the warm side. In hot climates any moisture that condenses on the exterior side of the vapor barrier will be drained to the exterior since the vapor barrier is also a drainage plane. Whether or not you need a vapor retarder hinges on three main factors your climate your home and the location of the wall you re insulating. Frame wall with cavity insulation and brick or stone veneer.

Vapor barriers are applied to the interior walls in climates which are predominantly cold while they are best applied to exterior wells in predominantly hot climates. A vapor barrier s job is to keep water vapor in humid air from diffusing through one side of a wall and finding a cool surface inside the wall. A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. Below grade walls and floor slabs transmit ground moisture through concrete walls or slabs.

This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards. Any condensation on a properly installed continuous plastic vapor barrier will. A continuous plastic vapor barrier prevents condensation from forming on the internal surfaces of the exterior wall.