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. Plastic vapor barriers should only be installed in vented attics in climates with more than 8 000 heating degree days. Seal the air leakage pathways. To heck with the experts here s my answer. 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. Not every wall does. No you don t need a vapor retarder class i or otherwise. 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.

You can forego the plastic and use a vapor retarder kraft faced insulation or latex ceiling paint in all other climates except hot humid or hot dry climates. Should a vapor barrier be used over attic insulation. In hot humid climates attics should not be vented and vapor retarders should not be installed on the interior of assemblies. The answer is no.

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. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. If your current insulation is a cellulose product similar to the greenfiber natural insulation your existing 6 is equal to about a r 19. Either install un faced fiberglass loose fill fiberglass or cellulose directly on top of the drywall.

Attic insulation and vapor barrier it is not necessary to have a vapor barrier for either greenfiber natural blow in or owens propink blow in insulation except if your local building codes require it. The vapor barrier is always installed facing the heated side of the wall or ceiling because that s where the moisture is coming from.