So I've been saving some scraps of lumber from work and decided to build a smoke house. I'm using 1/2'' OSB and 2x4. The smoker is 5'x2' with 4' being the chamber with 4 racks, and 1' being for the fire, using propane I think. I finished the framing for the most part and am wanting to insulate. I saved some R-30 extruded polystyrene insulation and was wanting to use that, but im not sure it would be safe, or withstand the heat or somethin. Any thoughts? I have OSB on the outside and inside with the insulation in between.