Non insulated cres cor build

[zhaley7777]

Has anyone ever used a non insulated cres cor for building a smoker? If so how did you insulate the outside besides welding tarps? Basically thought about building a shell that be a roof with the walls hanging from that down the sides out of 2x4’s and insulating between the studs and covering with plywood but wasn’t sure how to insulate the door. Any help is appreciated. Would like to build it electric 220v