Exterior Wall Moisture Barrier

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

Exterior wall moisture barrier.

In any case the vapor barrier must point to the warm side. This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards. If water vapor diffuses or infiltrates into the wall cavity and finds the cool surface moisture problems can occur. The first design concept is the barrier system where all moisture is resisted by the exterior surface material also often.

Not every wall does. Very hot and humid climates may benefit from an exterior vapor barrier that keeps outside humidity from penetrating into walls. Of course you can have moisure problems here even without the exterior vapor barrier because of what bill rose calls the rule of material wetting. Dupont tyvek drainwrap is a moisture barrier designed to provide enhanced drainage in areas subject to extreme wind driven rain.

A vertically grooved surface provides added protection against water by enhancing drainage away from the wall assembly. 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. The standard installation of a plastic vapor barrier is between the studs and the drywall but there are some exceptions to this.

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. The exterior face of the wall or floor cavity should remain permeable in order to allow dissipation of any moisture that does enter the wall cavity. In exterior walls that are below grade like basement walls. 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.

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. The cool surface is the sheathing assuming no exterior insulation. In designing exterior wall systems moisture infiltration is controlled following two basic design concepts or strategies. Whether or not you need a vapor retarder hinges on three main factors.