Vapor Retarder In 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.

Vapor retarder in attic.

Even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic. 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. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Some regions don t require a vapor barrier.

A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days. Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home. In circumstances where conditions inside a home or office are much different than outdoor conditions water. 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.

Resolution of the vapor barrier debate. Frame wall with cavity insulation and brick or stone veneer with interior vapor barrier. The ability of a material to retard the diffusion of water vapor is measured in units known as perms or. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective.

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. 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. Some debate still occurs over how necessary vapor barriers are but a consensus is growing closer. Attic vapor barrier detail for cold climates.

A vapor barrier or vapor diffusion retarder is a material that reduces the rate at which water vapor can move through a material. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic. The older term vapor barrier is still used even though vapor diffusion retarder is more accurate.