Another major consideration in every greenhouse construction: The north wall. One of the weaknesses of most greenhouses in a cold climate is the cold north wall. It is the biggest source of cold and loss of stored heat in a free-standing structure. There’s no such thing as too much insulation on the north wall. This explains why a pit greenhouse or a greenhouse with a large dirt mound against the north wall is so successful. These solutions keep the cold away from the north wall. In my case my insulated, and internally heated, home south wall was my backdrop. This alone guaranteed a certain amount of passive success. Give this subject lots of serious thought as you make your plans. It will be easy to heat any grow frame or greenhouse in northern Arizona because of our combined altitude and latitude. Keeping the heat overnight will be the challenge! This concept and the principles that make an insulated grow frame work are illustrated and explained in deeper detail in my article, “From Cold Frame to Grow Frame,” in the Solstice Report Issue Two. It seems simple but most greenhouses I visit fall short and must be cooled or heated in order to keep their plants alive. I have a friend who invested over ten thousand dollars in a purchased greenhouse, with double glazing and an 800-gallon water tank for mass storage. In the winter he must still run an electric heater all the time to avoid freezing, simply because the structure is 100% glazed and the collected heat can escape just as fast as it was gathered. It’s a wonderful structure but a failure in terms of being passive. Management of the internal environment is mandatory and the secret to success.

Picture 14 indicates the base beneath a platform I installed in the grow box before filling it with soil. I covered these with some of the cement blocks I used in the walls. This provides me with a place to stand or squat while I plant, weed or harvest. Picture 15 shows clamps holding wood rails as they dry (everything was glued and screwed) that act as guides for my glass panels and screens when they are in place. Picture 16 is the nearly finished grow frame. All it lacked here was the exterior wood paneling, which I added the next Spring. You can see the front supports that hold the glass doors are removable providing me with a totally open structure when I want to work on the soil, do maintenance, chase pests or add a trellis.