KenKrupa

Hi Joe_Bob,

Thanks for the reply. If I read it right, you would NOT have a vb on the exterior side of the wall, so I'm guessing you would have a vb on the interior side, right? If so, it seems like the polyiso is what's wrong here, and not the plastic. That would jibe with what I learned in school.

I'm not a homebuilder - just a do-it-yourselfer. I don't understand the vapor barrier thing in this puzzle. I've always understood that a vb was needed on the INSIDE of a wall - otherwise moisture will condense within the fg insulation. So I thought the plastic was good. Can someone explain why this is not so?