Vapour Barrier Attic Floor

Very hot and humid climates may benefit from an exterior vapor barrier that keeps outside humidity from penetrating into walls.

Vapour barrier attic floor. To know if you need a vapor retarder ask yourself a few basic questions. Attic vapor barrier detail for cold climates. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. Begin the process of fitting a vapor barrier for attic insulation by preparing the space for the job.

Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic. In the typical crawl space with a dirt floor a 6 mil plastic vapor barrier is used to prevent moisture from the soil from coming up into the crawl space area. Some regions don t require a vapor barrier. That vapor barrier is laid directly.

Even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. 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.

In any case the vapor barrier must point to the warm side. A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. 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. This vapor can become trapped inside walls resulting in mold and mildew growth which can damage your home and present a potential health concern.

Whether using loose fill or batts put the vapor barrier closest to the warm side of your installation where hot moist air would get in facing the house s interior in cold climates beneath floor insulation and the attic s interior in hot climates on top of floor insulation. Everyday activities such as cooking washing and bathing add moisture to the air in your home in the form of water vapor. Below grade walls and floor slabs transmit ground moisture through concrete walls or slabs. This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.

Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.