I am insulating my rim joists with rigid foam board in a manner similar to that described on the familyhandyman's website.
I am considering adding a second layer of foam board to get closer to the neighborhood of R20, which I've seen recommended for rim joists. I am wondering where would be best to caulk - after the first layer, second layer, or both?
Given that the caulk's purpose is to stop air flow, it would seem unnecessary to have two layers of it, but I am including "both" as an option in case you want to argue for it.
I can't really think of a difference between applying after the first layer of insulation or the second...can you?