Resolution of the vapor barrier debate.
Vapor barrier over rigid foam insulation.
The rigid foam will not absorb moisture.
It will degrade its r value.
Not every wall does.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
It will also allow shorter fasteners to be used and no guesswork about stud locations when installing the new insulation and wall coverings.
To complete the vapor barrier you would want to foam seal or tape all the sides where the rigid meets timber because these gaps will facilitate vapor flow.
Some debate still occurs over how necessary vapor barriers are but a consensus is growing closer.
After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
However an installation between the studs can pose a challenge.
Keep foam board insulation away from direct sunlight prior to installation.
In any case the vapor barrier must point to the warm side.
However please be aware that spray foam is not the same as rigid foam.
In circumstances where conditions inside a home or office are much different than outdoor conditions water.
Cover the insulation with a vapor barrier before you install it.
However an installation between the studs can pose a challenge.
By installing the crawl space vapor barrier over the insulation you will prevent holes in the vapor barrier from securing the rigid foam to the wall.
When installing the foam use caulk or tape for maximum insulation between the material and the board or floor.
It goes without saying that the holes would not be a good thing.
Rigid foam insulation is usually a qualified vapor barrier.
Avoidance of the installation of vapor barriers such as polyethylene vapor barriers foil faced batt insulation and reflective radiant barrier foil insulation on the interior of air conditioned assemblies a practice that has been linked with moldy buildings lstiburek 2002.
Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home.
Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets.