I am planning on insulating the floor under my three season porch; what would be better, kraft-faced bats of R-38 with the vapor barrier towards the floor, or two layers of R-19, with one face of thevapor barrier towards the floor, and the second layer towards the ground? The floor joists are 2 x 12's, and is about 18" off of the ground. Second question; I would like to put something over the insulation in an attempt to stop critters; I was thinking thin plywood, any other suggestions? And last question; the rafters are 2x10's; I know that the insulation should not touch the underside of the roof; I planned on ripping strips of 2" styrofoam board, and with that rip the board to 14.5" wide to create a "chase", and on toop of that, use R-19 fiberglass. That combination should give me R-29; any thoughts?