I've finished cutting the timbers for my 12'x24' cottage, and now I'm planning next steps. My floor joists and rafters are 4"x6" Hemlock, on 2' centers. I plan to do the floor in 2" T&G Kiln dried Hemlock (planed to 1 1/2"). The ceiling will be 1" T&G Hemlock, planed to 3/4". My problem is that I want to insulate the floor and ceiling, and I'm not sure how do to that. Do I effectively have to make two floors and two ceilings, with rigid insulation in between? What about an air space in the roof?