Air barrier continuity
I am working on total renovation of a 1950's ranch with a basement that walks out to grade. The roof and framed wall assemblies described below describe how the home will be renovated.
1) Roof assembly: 2x10 rafters, 1x4 board sheathing, peel-and-stick waterproof membrane, 8" reclaimed polyiso ((4) 2" layers), OSB, tar paper, standing seam metal roof
2)Exterior framed wall section: 2x4, OSB, tyvek drain wrap, (2) 2" reclaimed polyiso, 1x4 rainscreen, wood siding
3) Exterior CMU walls: 2x4 framed wall, 2" reclaimed polyiso, drainage mat, CMU, parging
The air barrier is not difficult to make continuous from the roof to the wall, as we have cut off all of the overhangs and will wrap the peel and stick membrane over the tyvek drainwrap. At the rim joist, we are applying peel and stick membrane to bridge the transition from framed wall/floor system to CMU (above grade). The membrane covers the top 3" of the CMU and then covers the rim joist and six inches above floor level. The tyvek drainwrap above will then over lap that membrane, all the way to the bottom of the rim joist. Because we have to insulate the basement from the interior I am wondering if I need an air barrier on the exterior above grade CMU wall? I am concerned with air passing through the pores of the block, getting into the block cavity (which is open at the top inside the basement) and making it's way into the house. My thought is I can either make my air barrier at the exterior face of the CMU or I will have to block the top of the block wall on the interior and spray foam the rim joist. My budget is tight and my gut says that an exterior air barrier would be more cost effective. Maybe a fluid applied air barrier? Thanks for any feedback / ideas.
Posted Sat, 06/21/2014 - 10:01
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