I’m doing some interior renovations in my 1915 Craftsman home in Florida and I have a room demoed down to the studs. 

I’d like to insulate the exterior walls while they’re open. The exterior is stucco over wood sheathing. 

Would it be appropriate to place rock wool insulation directly onto the wood sheathing between the studs? Does this type of application need some type of air gap or vapor barrier?