A common misconception is that all insulations require vapor barriers in all situations.
Blown attic insulation vapor barrier.
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.
This worked well until we added large quantities of attic insulation.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
Hence the need to reduce moisture flow into the attic and the need for a vapor barrier.
Some regions don t require a vapor barrier.
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.
After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
Attic insulation new construction or retrofit work.
Research has shown that this is incorrect.
R value declines by as much as 50 percent at temps below 0 degrees f.
The heat being lost from the house below warmed up the attic so that moisture was lost through the vents as vapor.
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.
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.
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.
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.
70 to 75 per sq.
Not every wall does.
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.