Do I Need A Vapor Barrier In My Attic

The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.

Do i need a vapor barrier in my attic.

Attic vapor barrier detail for cold climates even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic. All attics vented or unvented should have an air barrier a properly detailed airtight drywall ceiling for example regardless of climate. In circumstances where conditions inside a home or office are much different than outdoor conditions water vapor is likely to move through wall cavities and can get trapped inside and a well installed vapor barrier is recommended. Vapor barriers can also be important for certain rooms where moisture levels are especially high.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. In hot dry climates your attic can be vented though like in hot humid climates you should not install any vapor retarder or barrier. Seal the air leakage pathways. Do not add a vapor barrier on top of the insulation in your attic since the paper facing on the existing insulation is the vapor barrier.

Omitting a ceiling vapor barrier by arguing that you have to let the moisture escape or because the house has to breathe out the top is actually correct in a way. 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. It s also incorrect in a way. No you don t need a vapor retarder class i or otherwise.

By the time you paint the drywall though you ve brought it into the class iii vapor retarder range between 1 and 10 perms and even less water vapor will diffuse through. However all attics vented or unvented and in all climates should have an air barrier such as an airtight drywall ceiling. Not every wall does. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

You have loose fill insulation in the attic which doesn t have a vapor barrier.