The Main House is constructed out of “Cob” or “Puddled Adobe.” This ancient construction method uses clay, sand and straw as a low-cost local material for high thermal mass construction. The difference between cob and adobe is that the clay/sand/straw mixture is formed directly on the stem wall instead of being formed into bricks. Heat passes through high thermal mass cob at the rate of about 1 inch per hour. Thus, if the wall is 2 feet thick, it would take 24 hours for heat to penetrate to the interior of the wall. When outdoor temperatures drop, accumulated heat reverses direction and travels towards the cooler temperatures outside the wall – without ever having heated up the interior of the house.