Double stud wall sheathing / air sealing
Thanks in advance for any suggestions/comments/advice.
I am in the framing stage of residential home in central NC (Zone 4A). The exterior walls have been designed as a double-stud 2×4 assembly.
The interior double stud has been spec’d to be sheathed with 1/2 in CDX w/ taped joints and r-15 Roxul batts, cavity insulation as dense-pack cellulose to r-20, and exterior double stud finished off with another 1/2in CDX, followed by WRB, 1/2″ vertical furring for rainscreen, 3/8″ horizontal furring (to accomodate for Hardie board and batt siding.
Although I was not responsible for the design of the home, as project manager I am responsible for implementing this design into a well built assembly.
My questions are:
1. Could the exterior wall’s sheathing be changed to ZipSystem and eliminate the need for a WRB and rainscreen? (This would be preferred, if possible)
2. If the Zip is used on the exterior double stud would air sealing/taping the interior sheathed wall still be necessary?
3. If we did end up having to use a conventional, sheet type WRB could we eliminate the need of a rain screen by using Tyvek DrainWrap or HydroGap.
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