WRB between panel siding/sheathing and studs in dry, mixed climate?
I’ll be building a new, small house in central Arizona, the cooler part of Climate Zone 2B, where summer days go from 70 at dawn to 100 or so in the afternoon and winter nights sometimes drop to 20 with days usually reaching 50. It can get noticeably more humid in the summer “monsoon” season, but nothing remotely comparable to the Southeast. I’ll be using SmartSide 4×8 panels as my siding and structural sheathing on 2×6 walls insulated with Roxul batts.
SmartSide requires a vapor-permeable WRB underneath it. After reading lots of articles and discussions here at GBA on WRBs, including using rigid foam insulation as such, my best choice, tight budget considered, seems to be an ordinary WRB like Tyvek housewrap. Moisture accumulation inside my walls does not seem to be much of a concern in my climate, given that I’ll be using airtight drywall with vapor-permeable paint on the interior, but I do wonder whether I should be concerned about the pumping effect I’ve read about with something as flexible as Tyvek attached directly to studs. I’m hoping that the springiness of the Roxul batts will make them press the Tyvek against the inner surface of the SmartSide enough to suppress any pumping motion.
Although I feel as if my plan makes sense, I’ve learned from experience that I’m quite capable of having overlooked something important. Would a WRB other than Tyvek be a better choice?
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