A while ago I read about a tarp on top of a pop-up to cut down on moisture. Haven't tried that yet... But, When I went out last weekend with my wife and 3 y/o son I set up my fatfish and a floor constructed of the puzzle piece style mats and as far as temperature goes, it stayed plenty warm with a Mr. Buddy "Big Buddy" when it was -40 outside. The only problem was, moisture would collect on the ceiling, run to the edges and then drip onto you while you were sitting in your lawn chair. I had both vents open all day/night but that only helped so much. Any ideas on how to cut down on the moisture?