As the ambient temperature falls into the 20s and 30s, the extra insulation and thermal mass of the Dave House South help it completely overtake the Andy Shack. By dawn on the 17^th, the Dave House South is 14 ^oF warmer than the Andy Shack. Despite the larger ratio between absorber and floor area, the Andy Shack cannot hold on to the heat as well as the Dave House and so falls behind. Also, the Dave House South is not as badly handicapped as the absorber to floor ratio suggests since the Energie Solaire panels are much better absorbers than the SkyMats used in the Andy Shack system. One strange thing about this graph is the spike in the ambient and sol-air temperature occurring in the early morning of the 16^th (almost like an aborted dawn).