Vapor Retarder In Attic

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

Vapor retarder in attic.

In circumstances where conditions inside a home or office are much different than outdoor conditions water. 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. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. Applicability limited to very cold subarctic and arctic regions.

Attic vapor barrier detail for cold climates. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. The ability of a material to retard the diffusion of water vapor is measured in units known as perms or. This wall is a further variation of figure 6 but now it has a class i vapor retarder on the interior a vapor barrier completely eliminating any inward drying potential.

Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic. Some debate still occurs over how necessary vapor barriers are but a consensus is growing closer. A vapor barrier or vapor diffusion retarder is a material that reduces the rate at which water vapor can move through a material.

On the other hand an air barrier a properly detailed air tight drywall ceiling for example in the absence of a vapor barrier can be effective since it stops the flow of vapor laden air. Even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic. 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. A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days.

If your climate does not meet these conditions a vapor retarder like latex ceiling paint will work well for your house if you are in all other climates except the hot dry and hot humid. Some regions don t require a vapor barrier. Frame wall with cavity insulation and brick or stone veneer with interior vapor barrier.