No Vapor Barrier In Attic Insulation

The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.

No vapor barrier in attic insulation.

Then cover the foam with drywall as required for fire safety. Before the introduction of attic insulation attics in cold climates were poorly insulated and plastic ceiling vapor barriers were omitted. Fiberglass insulation must stay dry to be effective. So for this top layer you would be purchasing unfaced insulation batts not rolls of an r value of at least 30.

After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Not every wall does. Foam blocks airflow needs no vapor barrier and has a higher r value per inch than loose fill or batts so you ll get more protection with less depth. The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor.

Experts say that if you are putting in a second layer of insulation you should have no vapor barrier between the two layers. With spray foam unlike with loose fill or batts you must cover the soffit vents they aren t needed to keep the roof cool. A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective. Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Vapor barrier up or down. The best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses.