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.

Do i need a vapor barrier in my attic.

You have loose fill insulation in the attic which doesn t have a vapor barrier. No you don t need a vapor retarder class i or otherwise. Seal the air leakage pathways. Avoid adding interior vapor barriers where the outer wall construction already includes a material with vapor barrier properties.

Most authorities recommend vapor barriers in certain situations. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. 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.

However all attics vented or unvented and in all climates should have an air barrier such as an airtight drywall ceiling. 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. 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. In areas with high humidity such as greenhouses rooms with spas or swimming pools and bathrooms vapor barriers are often recommended.

A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. In hot dry climates your attic can be vented though like in hot humid climates you should not install any vapor retarder or barrier. Not every wall does. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic.