Blown Attic Insulation Vapor Barrier

After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.

Blown attic insulation vapor barrier.

70 to 75 per sq. The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. With the added insulation the attic stayed cold and so did the ventilating air from outside which was now unable to effectively remove attic moisture. A common misconception is that all insulations require vapor barriers in all situations.

The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor. Attic insulation new construction or retrofit work. This worked well until we added large quantities of attic insulation. Now with attic insulation heat is no longer lost from the living space such that moisture may remain trapped in the attic vapor barriers were therefore necessary to reduce moisture flow into the attic.

Whether using loose fill or batts put the vapor barrier closest to the warm side of your installation where hot moist air would get in facing the house s interior in cold climates beneath floor insulation and the attic s interior in hot climates on top of floor insulation. Hence the need to reduce moisture flow into the attic and the need for a vapor barrier. Do not add a vapor barrier on top of the insulation in your attic since the paper facing on the existing insulation is the vapor barrier. R value declines by as much as 50 percent at temps below 0 degrees f.

Cima does not recommend the use of vapor barriers with cellulose insulation except in circumstances of exceptionally high moisture levels such as an indoor pool facility or very cold climates. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below. But in some cases water vapor builds up in tight houses until it forces its way through the inside wall surface the vapor barrier and insulation hitting the back of the cool sheathing then. Fluffy bits of spun glass that are noncombustible and can t decay.

Attic vapor barrier detail for cold climates 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. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.