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. Vapour barrier is on the top of the rafter then insul then board if heating garage insul vapour then board need hatch for summer to let out hot air i m a insulator typar is a better product in a. The theory is that part of the moisture vapor in the house is actually blocked by the drywall and paint on the. Seal the air leakage pathways. No you don t need a vapor retarder class i or otherwise.

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. 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. 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. Not every wall does.

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. 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. You have loose fill insulation in the attic which doesn t have a vapor barrier. However all attics vented or unvented and in all climates should have an air barrier such as an airtight drywall ceiling.

It s also incorrect in a way. In hot dry climates your attic can be vented though like in hot humid climates you should not install any vapor retarder or barrier. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. 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.