Does attic floor need vapor barrier?

All attics — vented or unvented — should have an air barrier (a properly detailed airtight drywall ceiling, for example) regardless of climate. Omitting a ceiling vapor barrier by arguing that “you have to let the moisture escape” or “because the house has to breathe out the top” is actually correct, in a way.

Can vapor barrier go on floor joists?

You want to lap the vapor barrier up the foundation walls and attach it to the wood sill plate that the floor joists rest on. Just tape all overlaps well so no vapor can escape into the crawl space. Once the vapor barrier is in place, you can add insulation in between the floor joists.

What is the minimum attic venting in an attic without a vapor barrier?

1/150
Attic Ventilation area shall be no less than 1/150 of the attic floor area if no vapor retarders are used, or 1/300 of the attic floor area when a vapor retarder having a permeance of one perm or less is used.

What material should use for attic floor?

Joist Spacing and Attic Use You need 3/4-inch plywood. The thinner plywood is acceptable when the joist spacing is 16 inches. If you plan to finish the floor in the attic and turn the room into a living space, however, you should always use 3/4-inch plywood.

How do I add vapor barrier to my attic?

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). The insulation (fiberglass or cellulose) is then placed on top of the drywall with no vapor barrier above or below.

Should I put a vapor barrier under my subfloor?

Vapor Barrier Blocks All Moisture Issues Concrete is porous in nature and will soak up any moisture that is in the ground and show up on the top of your concrete. So we recommend vapor barrier for all flooring installation that have a concrete subfloor.

When should I use vapor barrier on floor?

Vapor barriers should be used on a floor when the area is prone to moisture. When moisture penetrates your flooring, it can cause mold, mildew, and the potential for water damage. A moisture barrier helps control the water vapor’s movement to help protect your floors.

When should you use a vapor barrier?

A vapour barrier is an important component in building construction. Its purpose is to help prevent water vapour from reaching building walls, ceilings, attics, crawlspaces or roofs, where it can condense and cause building materials to rot or grow mould.

What happens if attic is not vented?

Insufficient ventilation can lead to moisture problems during the winter and decreased energy efficiency during the summer but too much ventilation can be just as bad, if not worse. Roof vents create an additional roof penetration, essentially another place of vulnerability where leaks can occur.

Can a vapor barrier be used in the attic?

Each one of those “penetrations” typically allows a significant amount of air and water vapor to move back and forth from the conditioned to unconditioned spaces. Even though we apply vapor barriers to exterior insulated walls in cold climates it’s no longer recommended for ceilings (floor of the attic).

What’s the best insulation for a vented attic?

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). The insulation (fiberglass or cellulose) is then placed on top of the drywall with no vapor barrier above or below.

Is there a vapor barrier between the ceiling and drywall?

The insulation (fiberglass or cellulose) is then placed on top of the drywall with no vapor barrier above or below. The latex paint allows the ceiling to breath a bit but still help prevent significant movement of air and water vapor. This really helps prevent trapped moisture between a traditional vapor barrier and the drywall.

Why is latex used as a vapor barrier?

The latex paint allows the ceiling to breath a bit but still help prevent significant movement of air and water vapor. This really helps prevent trapped moisture between a traditional vapor barrier and the drywall. Should A Vapor Barrier be Used Over Attic Insulation?