I have an integral garage with a small bedroom (used as a study) above it that gets bitterly cold and I'm looking at ways of insulating. Ripping up floor-boards and stuffing between the rafters might be a longer term solution, but for quickness I'm looking at sticking thermal board to the underside of the garage ceiling. It doesn't really matter (too much) what it looks like, though in time, I might want to plasterboard and paint. Does anyone have any thoughts on what's the best board and method of attachment?