I have 2 inches of foil-faced polyiso over Typar on the exterior of my north wall. It is strapped with vinyl over the strapping.
How much interior insulation can I have on this wall, and do I need an air barrier? Reason I ask about the air barrier is because some of the gable wall space is behind the kneewall where I really don’t feel like hanging sheetrock or paper unless I really have to…
Also, can I use XPS on the interior or will this create a double vapor barrier? I’m in zone 6.
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