A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
Attic insulation moisture barrier.
Most forms of attic insulation benefit from the addition of a vapor barrier to protect them from the harmful effects of moisture which can reduce their effectiveness over time the following are a few simple steps to help you undertake the task properly so your vapor barrier retains heat without damaging the insulation.
Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
Vapor barriers keep the air moisture in your house from condensing in the insulated cavities.
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.
If installed on top of attic floor insulation the foil will be susceptible to dust accumulation and may trap moisture in fiber insulation so it is strongly recommended that you not apply radiant barriers directly on top of the attic floor insulation.
If you live in a cold climate place the vapor barrier between the interior of your home and the insulation.
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.
Not every wall does.
In any case the vapor barrier must point to the warm side.
When adding additional insulation to an attic that is already insulated never use insulation with a vapor barrier.
Over time this trapped moisture can rot the wood framing in your attic or cause mold and mildew to appear.
Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.
If you do there is a chance that moisture that has slipped by the first vapor barrier will become trapped by the second vapor barrier decreasing the value of your insulation.
Whether your vapor barrier is a facing or a film it must be placed on the warm in winter side of the wall.
Some regions don t require a 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.