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.
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.
Research has shown that this is incorrect.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
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.
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.
70 to 75 per sq.
The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.
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.
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.
Fluffy bits of spun glass that are noncombustible and can t decay.
Attic insulation new construction or retrofit work.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
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.
Some regions don t require a vapor barrier.
Not every wall does.
R value declines by as much as 50 percent at temps below 0 degrees f.