hi all, I have have a 30x40 pole barn that I currently have a wood stove in. im thinking about getting a large propane heater and venting...looking for recommendations on type and amount of btus I might need. I have 16 ft side walls and open rafters...insulation wise I have 2 inch foam board on the walls..covered with plywood....r10 equivalent and the gables and roof have been spray foamed...2 inches on the roof....1 inch on the gables with 2 inches of foam board behind it. I'm in indiana...any recommendations would be of help..thanks!