So like I have this enclosed space underneath my stairs and it's got a door and siding on it. My neighbor and me decided to make it into a sort of clubhouse thingy. It's about to be winter so it's going to be cold, and so we thought we might need insulation to make it, well, not cold. On the inside there's only the outside siding to keep it closed. So how would I go about insulating it and then making a wall of wood or something?
