Looking at insulation for my Shorty, I don't want to lose too much space due to height limitations as I'm 6' and the bus is 73" +/- at bare metal. What do you all think of doing a standard wood frame and 1" thick foam insulation squares/rectangles that is most common and then have a ~1/2" air gap and Reflectix (or similiar) rolled out and then the plywood subfloor on top of that?
Does the Reflectix need an air gap on both sides? Would it be more beneficial to just double up on the 1" (or change to 3/4" and double those) and then the plywood directly over those and skip the air gap and Reflectix? I'm considering this for floor, walls and ceiling. Reflectix and the wood I'm considering for the ceiling wouldn't amount to much space lost and the Reflectix under the subfloor wouldn't amount to much either and it would be an additional barrier.
If I were to do this, should the foam board insulation be foil backed and have foil on either side of the air gap (foil of the foam facing up from the floor and then the gap with Reflectix on top of the gap) or just standard foam board without foil? Or foil down?
...these are the things that keep me up at night, my girlfriend is starting to think I'm cheating and thinking about another girl!