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Wall Assembly Climate Zone 5

JennL | Posted in Expert Exchange Q&A on

Building in CT (climate zone 5). The wall assembly will consist of vinyl siding, Tyvek wrap, plywood, Knauf Ecobatt insulation, drywall, and latex paint. I believe that codes require a class II or III vapor retarder. I am extremely sensitive to mold. Given a choice between Kraft facing or several layers of latex paint, which is the better option? I plan to use low VOC paint. I’ve called several manufacturers and they apparently do not test permeability for interior latex paints. Will the inspector require perm ratings? The builder will be giving special attention to air sealing including a blower door test prior to drywall installation. 

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  1. Expert Member
    PETER G ENGLE PE | | #1

    With that wall system, kraft paper facing on the FG batts is enough VR to limit condensation and chances of mold growth due to condensation. A coat or two of latex paint will also help, but is not the primary VR. In my experience, mold in walls is caused far more often by poor exterior flashing and sealing details than by diffusion or air leakage from the interior. Make sure your builder uses best practices with the exterior envelope water protection.

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