Retrofit: Partially replacing kraft-faced fiberglass with closed-cell spray foam
I’m looking for some practical feedback on whether replacing kraft-faced fiberglass with closed-cell spray foam in some exterior partitions—but not all—potentially invites future frustration.
We’re working through a partial retrofit of several rooms of a 30-year-old 2×4 framed house and the architect has proposed to replace old kraft-faced fiberglass batts with closed-cell spray foam while our exterior walls are open. We’re concerned that having facades with both closed-cell spray foam (R-24, 0.23 perms) in some areas and fiberglass (R-13, 1 perm) in other areas will create moisture challenges when we eventually replace the exterior and want to add continuous insulation on the outside.
If we have exterior walls that are part fiberglass and part closed-cell foam (but not in the same stud cavity), are we inviting condensation issues if we later add continuous insulation around the outside? Or will we just need to install thicker exterior insulation around the whole house to both preserve the proper ratio and achieve uniform wall thickness? Alternately, are we going to invite problems if we never get around to the exterior insulation project?
We’re in Chicago, zone 5A, so we get an invigorating mix of hot and humid and deep freeze. Any suggestions or alternate approaches are appreciated.
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