Do You Need a Vapor Barrier in Pole Barn Walls?

It depends on the insulation. Closed-cell spray foam at about 1.5 inches or more acts as its own vapor retarder, so no separate plastic is needed. With fiberglass, the facing is the vapor retarder and every seam has to be sealed. House wrap like Tyvek is not a vapor barrier.

What a Vapor Barrier Does

A vapor barrier or retarder slows moisture moving through a wall. In a metal pole barn, its job is to keep warm, moist interior air from reaching the cold steel, where it would condense.

With Closed-Cell Spray Foam

Closed-cell foam bonds directly to the metal, so there is no gap for air to reach the steel, and at about 1.5 inches it slows vapor enough to act as a vapor retarder. Adding plastic sheeting on top is usually unnecessary. See pole barn spray foam insulation.

With Fiberglass Blanket

Faced metal building blanket relies on its facing. Tabs and seams must be taped, and torn spots repaired, or moist air gets behind the fiberglass and condenses on the panels. See fiberglass pole barn insulation.

Can You Use Tyvek Instead?

No. House wrap is designed to stop air and liquid water while letting vapor pass through, which is the opposite of a vapor barrier.

Don't Forget the Floor

A slab poured without a vapor barrier, or a dirt floor, can release a lot of moisture into the building. That moisture has to go somewhere, and in winter it ends up on the coldest surface.

Pole Barn Insulation Pros Tulsa offers free on-site estimates and written quotes seven days a week, 8am to 7pm. Call (918) 880-2499 or request a free quote online.