Is a thin layer of rigid foam better or worse than nothing?
I am building near Madison, WI. Our house plan has walls that consist of (outside-in): Cedar or Hardieplank, tyvek, 7/16 OSB, 16″ on center-studs, R23 bib insulation, 6 mil vapor barrier, drywall. My question is whether 0.5″ of rigid foam insulation added to the exterior, inside the Tyvek will do more harm than good. I gather it will reduce thermal bridging, but it is too thin and may lead to moisture problems. I know 1.5 to 2″ of rigid foam is the correct thickness. So the question is, should I just ditch the foam?
Thanks in advance.
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