Does a Wall in Wyoming Need a Vapor Barrier?
Yes. Wyoming’s 23 counties fall entirely within IECC Climate Zones 6B, 7, and 5B, none of which qualifies for the code’s warm-climate exception.
Does a Wall in Wisconsin Need a Vapor Barrier?
Yes. Wisconsin’s 72 counties fall into IECC Climate Zones 6A (42 counties) and 5A (30 counties), and the 2021 International Residential Code exempts only…
Does a Wall in West Virginia Need a Vapor Barrier?
Yes, in most cases: West Virginia’s 55 counties sit entirely in IECC Climate Zones 4A and 5A, and the 2021 International Residential Code requires an…
Does a Wall in Washington Need a Vapor Barrier?
In Washington, a vapor retarder is required on the interior side of frame walls, and it applies to the whole state.
Does a Wall in Virginia Need a Vapor Barrier?
Yes. Virginia sits mostly in Climate Zone 4A, with 19 counties in Zone 3A and 5 in Zone 5A carved out as exceptions, and none of those three zones…
Does a Wall in Vermont Need a Vapor Barrier?
Vermont sits entirely in IECC climate zone 6A, and that single fact settles the question: under the 2021 International Residential Code, a frame wall in…
Does a Wall in Utah Need a Vapor Barrier?
Utah spans three IECC climate zones across its 29 counties: Zone 5B covers 21 counties, Zone 6B covers 7, and Zone 3B covers just 1.
Does a Wall in Texas Need a Vapor Barrier?
The IRC exempts Climate Zones 1, 2 and 3 from the interior vapor retarder requirement.
Does a Wall in Tennessee Need a Vapor Barrier?
Tennessee doesn’t give one answer. In the state’s 61 counties that sit in IECC Climate Zone 4A, the 2021 International Residential Code calls for an…
Does a Wall in South Dakota Need a Vapor Barrier?
South Dakota’s 66 counties sit entirely outside Climate Zones 1, 2 and 3, which means the 2021 International Residential Code’s exception for warm…