1) How far down the wall do I insulate with the foam board insulation? In other words, do I need to go below the existing dirt floor of the crawl space with the insulation? 2) When I put the poly over the ground, do I cut it so it does not touch the wall, or leave it a little long? Do I need to secure the poly, to the Foam board, with some sort of tape? 3) Do I need to actually heat the crawl space, or will enough heat radiate through the floor to prevent condensation?