Single wall is what you want. Double wall is more insulated, but you want the pipe to radiate heat into the space. We use them in tents, and you need a stove jack- something non-flammable where it goes through the roof- they make these. We ended up making a galvanized sheet metal reflector that stood behind the stove, and reflected the heat from behind the stove forward. That kept the canvas from getting toasted when the stove was roaring.