When a home is situated thoughtfully, it will derive most of its heating needs at no cost from the sun. During the colder months when heat energy is required, the home allows solar radiation in from the South. During the day, the sun’s warm energy pours in the south-facing windows and heats the thermal mass of the concrete slab. You will not notice the air temperature rise as all that energy is stored for the evening. Older ‘passive solar’ homes here in the Baca had overheating problems due to way too much glass and not enough insulated, thermal mass to store the heat. It would overheat in the day and get too cold at night. We now know better and it is possible to design a home with the right amount of Southern glazing, the correct amount of thermal mass and the appropriate insulation.
When the sun sets, the magic begins. The air temperature starts to drop in the home with no incoming radiation. As the air temp starts to decrease, the warm thermal mass begins to release its stored energy into the air and warms the house and its occupants. This combination of mass, glass, insulation and a tight building envelope, will create a long lasting and ever-comfortable home, no matter the conditions outside.