Watauga River Farms is home to three experimental greenhouses built by Appalachian State University’s Department of Technology. The greenhouses are heated entirely with passive solar heat using natural heat storage.
Two of the greenhouses use underground pipes to keep the ground temperature at seventy degrees all year. The system circulates the hot air from the top of the greenhouse through three layers three layers of pipes running under the floor of the greenhouse. Additional insulation at night is provided by a foam of soap suds pumped into the walls to form an insulation blanket. The foam drains out at night into a holding tank.
The third greenhouse has no underground heat, but stores heat like the other two greenhouses. Black barrels and jugs hold water that has also been dyed black. The water stores heat throughout the day and releases the heat through the night.
Chard planted in October grew well in all three greenhouses throughout winter without slowing down. Sugar Snaps planted in February produced well until late June. Charles is interested in plants that will climb or produce continually, and is experimenting with different greens to see which perform the best in winter.
Charles is planning a fourth, larger greenhouse incorporating improvements based on what he has learned from the three smaller greenhouses. This new greenhouse is planned to be at least one hundred feet long and thirty feet wide. The back wall will be underground to take advantage of the constant fifty-five degree ground temperature found three feet below the surface. This greenhouse will have an insulated covered roof and will not use additional underground heat. Hot water heat may be incororated by stacking barrels three runs high along the rear wall.
