SPF thickness under roof deck
We are building a pole barn house. I’m located in Southeastern Ohio. We have the shell completed. It was built with 1/2 rigid foam under the metal. It was built with a completely sealed house in mind and to use an HRV/ERV for fresh air as well as a ducted/non ducted minisplit combo for heat and AC . My question is how many inches of Closed Cell SPF should I put under the roof deck and in the walls? I’m thinking 4″ under the roof deck and 1.5 in walls then finish the wall cavity with rockwool. The walls are very thick. Part of my reasoning is we have a 30×40 pole barn that has approximately 2.5″ of SPF under the roof deck and 4″ in the walls, the building is in direct sunlight most of the day. A 12k btu Mitsubishi Mini Split keeps it 70 degrees even in 90+ temps. Am I thinking right?
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