We have installed a lean-to type greenhouse on the South side of our block-and-concrete growing facility, which stays covered (double poly with inflation) from Labor Day through Memorial Day. To our pleasant surprise, not only are we able to provide almost all the heating needs for our concrete growing facility, but we are also able to keep the structure above 45°F at night and below 88°F in the day, which is perfect for growing plants. Thanks to Eric, we have a complicated thermostatically controlled environment, which allows us to store excess heat from the greenhouse in the concrete mass of the main growing building during the day, and return it to the greenhouse at night to prevent freezing. Utilizing properly sized thermal mass temperature storage at our latitude allows for no heating or cooling expense for the entire spring and autumn seasons. The typical cubic feet of air in a building, if condensed to the density of cement, will take up the space of approximately one cement block. The denser the material, the more heat it can store. There is no need for additional heat in the Mid-west when we allow the heat of a spring or autumn day to be stored in cement blocks or brick and then re-radiate into the structure during the colder night.