Best unvented shop ceiling option
I’m building my metal roofed work shop in climate zone C4. Because of the pole barn and shed roof purlins I won’t be able to vent the ceiling assembly. I’m planning on using spray foam directly against the underside of my roof sheathing because if this. I have a choice of either using 3” of spray foam or for less money, I can use 2” of spray foam and a R13 fiberglass bat. Which is best? Code for living space in our area in a ceiling is at least 3” of spray foam, but this is a shop and the 2” plus bat option is cheaper and has a higher overall R value. I am concerned about moisture as I could be doing some wet work in the shop. Any advice would be appreciated.