Do I Need A Vapor Barrier In My Attic

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

Do i need a vapor barrier in my attic.

Hi beth 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. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the 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. Most authorities recommend vapor barriers in certain situations.

Avoid adding interior vapor barriers where the outer wall construction already includes a material with vapor barrier properties. 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. Seal the air leakage pathways. 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.

You have loose fill insulation in the attic which doesn t have a vapor barrier. Not every wall does. 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. 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. No you don t need a vapor retarder class i or otherwise. However all attics vented or unvented and in all climates should have an air barrier such as an airtight drywall ceiling. In hot dry climates your attic can be vented though like in hot humid climates you should not install any vapor retarder or barrier.