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EC IL | The OP’s question was about adding house wrap. If you have a vapor barrier behind drywall and put house wrap on the sheathing, your wall will rot because as you stated the wall has to dry to the outside. The reason for this problem is that 99.99% of the installed vapor barriers are ineffective at preventing 100% moisture migration due to how we install the barrier with staples and do not seal over the staples, then we cut holes for switches and outlets in the barrier and cannot seal the vapor barrier to the outlet nor seal the holes in the back of the electrical box where the cables enter it and lastly, even if everything else on the installation was perfect we put dozens of drywall screws through the vapor barrier.
This is why closed cell spray foam is so effective if installed correctly. The 100 penetrations on every 10’ of wall to install drywall are effectively within the conditioned space of the home. Moisture does not have the opportunity to reach a cold surface and condense. Within a spray foamed wall though, very hard types of lumber like old growth Douglas fir and southern yellow are a little like having steel studs and they will be a cooler surface within the enclosed stud cavity but generally not cold enough to condense moisture. | |
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House Wrap-How Much Does it Help?
