How Much Spray Foam
I'm building my bus for winter camping in what could be extreme cold (-20'F at night). I'm planning on 2 in xps board on the floor and 2 inches of spray foam on the walls and ceiling. The windows will have 2 inch foam board covers for when it is really cold. This should give me about an r-12 all the way around. The front of the bus (windshield, entry door ect.) will be separated and insulated from the living area. I plan on using a 10kw (34,000 btu/hr) espar diesel coolant heater as a heat source. Is this enough insulation to be able to practically heat the bus in these condition? I could go thicker at the expense of headroom and floorspace.
To those of you with foam insulation that have stayed in cold climates how thick is your insulation on walls, ceiling and floors? How easy was it too heat the bus at the coldest outside temps encountered? What did you use to heat your bus and how many BTUs? Also how well were your windows insulated?