Guest User
3/7/2006
Is there a difference between air, vapor, and moisture barriers? What are recommended barrier materials?
Allan Reid
Dura-Loc Roofing Systems, Inc.
3/8/2006
Unfortunately homes are changing faster than the building code. The code calls for vapor retarders on the inside and outside of the roof. Certainly in climates the go below dew point one should be using a 10 mil thich poly air barrier sealed at all joints. Every hole in this barrier will allow one cup of water through a year.I refer to this material as an Air barrier with a very low perm (water transmision) rating. This stops the movement of warm moist air through the assembly and condensating on the outside. Then one must install anour vapour retarder under the roof covering. This is to collect condensation and stop it from entering the assembly. In severe weather climates critical areas of the roof should have a low perm rated materil but otherwise a loose laid felt paper is sufficient.
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