Air sealing already-sheathed new construction?
Hi there. I’m building a 1200 sqft addition in the Seattle area (Zone 4 Marine/Coastal). I am attempting to use the sheathing as my primary air barrier, with Tyvek CommercialWrap as my WRB underneath 1.5” inches of rockwool, a 3/4” rainscreen/air gap, and Hardie plank siding. The plan is to use the Tyvek as a backup air barrier— taped (vertical seams) and sealed (Prosoco AirDam bead on underside of Tyvek at all horizontal seams [extending over the top and bottom plates/sills]). While I had my contractor caulk the mudsill to the foundation and fill exterior sheathing seams with Prosoco Joint & Seam, a miscommunication has left all plywood sheathing uncaulked to the rims, sills, and framing (it is, in many places, nailed to schedule as shear walls… maybe that makes it tighter?). I will not be conditioning or encapsulating the attic or crawlspace, so getting my air boundary appropriately “single unbroken line”-ed at the top and bottom of my exterior walls is, I think, fairly important. I’ve attached some photos as examples of the current state of the build.
Now that the sheathing is up and the roof is on — but framing is all still wide open on the inside— what’s the best way to seal my sheathing at the top and bottom edges?
And is there any point to air sealing sheathing wall seams at the gables (at least any taller/higher than the blown-in insulation in my attic will tend) if my attic will be vented?
Thanks in advanced! His community is amazing.
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