Tyvek window detail not air tight?
I can’t wrap my head around the Tyvek window detail. I think it allows air to enter the building or maybe I’m just overthinking this.
Regular 2×4 stud wall with ply sheathing. Sheathing seams and window rough openings are taped. Next, Tyvek is installed according to their instructions: cut at windows and wrapped around the jambs, stapled to the inside of the jamb stud. Sill is flashed with Flex wrap. Then the nailing fin windows are installed and flashed.
Im using the Tyvek as my water barrier, not my air barrier (bottom is not taped). My air barrier is the taped sheathing along with spray foam insulation.
So since air can get behind the Tyvek, from there, wouldn’t it be able to move to the inside of the building as indicated on my sketch? Am I missing something?
Should I have followed the alternate Tyvek installation method where windows are placed before the Tyvek?
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