Vapor barriers are not typically intended to retard migration of air. When this air moves from location to location due to an air pressure difference the vapor moves with it.
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This can lead to rot and mold.
Insulation vapor barrier direction. A few years ago jlc took a look at the new crop of smart vapor retarders represented by. In recent years as new materials have entered the industry the topic has only gotten more complicated. In cold climates the opposite is true.
In warm climates the barrier should point to the outside of the house blocking the vapor from the humid outside air that may seep into the walls or ceilings. Confusion on the issue of vapor barriers and air barriers is common. Install small circular plug vents between the studs on the exterior of the house.
The confusion arises because air often holds a great deal of moisture in the vapor form. Use a vapor barrier paint to slow down the movement of moisture into the trouble spot. The function of a vapor barrier is to retard migration of water vapor.
Where it is located in an assembly and its permeability is a function of climate the characteristics of the materials that comprise the assembly and the interior conditions. Foil is a true vapor barrier and if you go that route you should avoid putting any other strong vapor retarders in the assembly. The air is usually warmer inside the house so condensation can build up from air entering the wall from the inside.
Eliminate sources of moisture in the basement and crawlspace. However stapling insulation in this manner creates and improper seating of the drywall during installation. Problems insulation and vapor barriers can cause.
This is a type of migration of water vapor. If the insulation is installed with the paper vapor barrier facing away from the heated part of the home moisture from humid inside air can condense and become trapped in the insulation during cold winter months. Vapor barriers are a complex subject and often a confusing one for contractors and tradespeople.
Also in nm with enough eps on the exterior there is similarly no need to put any vapor retarder on the assembly and it will be far more resiliant if done without vapor retarders. The two staple tabs of insulation paper laid on top of each other to the nailing surface of the stud would seem to be an imperceptible discrepancy perhaps a 116 or less.
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