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Dual vapor barrier wall assembly

Dual vapor barrier wall assembly

Dual vapor barrier wall assembly

I have a home where the walls are constructed as follows from the inside out: gypsum board, plastic sheeting, 2x4 studs with blown in cellulose insulation, asphalt impregnated fiberboard exterior sheathing with Masonite siding. The homeowner wants to remove the Masonite siding, repair any damaged fiberboard sheathing, add a layer of OSB sheathing with a moisture barrier, and install new vinyl siding. The addition of the OSB sheathing is because he doesn't like the idea that someone can literally cut their way into his home with a box cutter which I don't blame him. If we remove the fiberboard sheathing then replacement of the the insulation would be required as well as the blown in cellulose is retained inside the wall cavity by the fiberboard sheathing and the plastic sheeting on the inside of the wall. I am worried that if we add the OSB sheathing with an additional moisture barrier on the exterior of the wall assembly we could get moisture issues within the wall cavities but I also don't like the idea of not adding a moisture barrier behind vinyl siding either. The homeowner resides in Charlotte, NC which experiences relatively mild winters and warm humid summers. I was curious to everyone's thought on whether the new proposed wall assembly consisting of gypsum, plastic sheeting, 2x4 studs with blown in cellulose, fiberboard sheathing, OSB sheathing, moisture barrier, and vinyl siding would present any potential for trapping moisture in the wall cavity? If so what if anything could be done to mitigate the potential for this to occur?

RE: Dual vapor barrier wall assembly

Ideally we don't double post around these parts. See my response to your query in the structural engineering forum.

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