What size would you build, mine is 26 Ft. x 26 ft. x 10 ft. to the rafters, if I were to do it again it would be 36 ft x 40 ft. minimum,. and don't forget the steel straps for the wind , and I covered the walls with 2" foam for the cold , yours for the heat, OS board , 2" foam and Os board over the foam and vynal siding finish, good luck with the project, de dee