We use 6 mil plastic stapled to an A frame made out of hardwood (frame lasts about 10 yrs.), then throw a plastic non tear tarp over the 6 mil and secure to the frame, then staple 3 mil plastic to the frame on the inside (gives dead air space for insulation ), throw in a wood burning stove (burn only seasoned hardwoods, sugar maple prefered if available), line the floor (ground) with indoor/outdoor carpet , fire up the stove and in short order your in your T shirt and underwear.