The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it.
How important is vapor barrier in attic.
In cold climates the primary purpose of attic or roof ventilation is to maintain a cold roof temperature to control ice dams created by melting snow and to vent moisture that moves from the conditioned space to the attic ventilation acts to bypass the vapour barrier created by most roof.
A vapor barrier in an attic assembly in a severely cold climate with the absence of an air barrier will likely be ineffective.
If your climate does not meet these conditions a vapor retarder like latex ceiling paint will work well for your house if you are in all other climates except the hot dry and hot humid.
Resolution of the vapor barrier debate.
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.
Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home.
Not every wall does.
On the other hand an air barrier a properly detailed air tight drywall ceiling for example in the absence of a vapor barrier can be effective since it stops the flow of vapor laden air.
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.
A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days.
Throughout the balance of this digest the terms attic and roof will and can be used interchangeably.
Vapor barriers are a must for protecting your home against the damaging effects of moisture and keep your crawl space dry.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
A vapor barrier is a thin layer of impermeable material typically polyethylene sheeting included in building construction to prevent moisture from damaging the fabric of the building.
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.
