Hello,

I am planning the build of a metal building in Oklahoma (hot and humid summers and mildly cold winters). I want to use Polyiso foam board as insulation for both the sidewalls and roof. My question is should I put the foam board against the metal or should I leave an air gap between the foam board and the exterior metal. It’s worth mentioning the foam board has a reflective surface on it and if I left an air gap I could use it as a radiant barrier. I want to avoid condensation on the  inside of the building, I don’t want it raining down on my shop and I don’t want water molding/mildewing between the metal roof and the foam board. Final question is should I use a house wrap or vapor barrier between the metal roof and the foam board or is the foam board enough of a vapor barrier. I plan on heating in the winter and eventually cooling via a mini split in the summer. Thanks.