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. Should a vapor barrier be used over attic insulation. 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. 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. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.

Not every wall does. 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. Either install un faced fiberglass loose fill fiberglass or cellulose directly on top of the drywall. The vapor barrier is always installed facing the heated side of the wall or ceiling because that s where the moisture is coming from.

After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Seal the air leakage pathways. No you don t need a vapor retarder class i or otherwise. Plastic vapor barriers should only be installed in vented attics in climates with more than 8 000 heating degree days.

Now let s look at your situation which is a little different. To heck with the experts here s my answer. In hot humid climates attics should not be vented and vapor retarders should not be installed on the interior of assemblies. 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. 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.