Greenhouse (con't)
The massive concrete arch was designed by a bridge engineer. It has a fourteen-foot span and is cantilevered six feet back from its base. It serves numerous functions. Most importantly, it distributes incoming solar energy throughout the building as heat and light. It prevents hot summer sun from reaching most of the back wall while at the same time letting in lower winter sun to heat much of the wall.
During construction, a one-hundred-meter-long, zigzagging polybutylene pipe was cast into the face of the arch. Heat stored in the mass of the arch during the day preheats water going to the storage tank heated by the active solar system on the roof, reducing the needed solar collector area by more than a third.
Air vents in the roof of the greenhouse and operable windows at the front of the building provide ventilation in the summer months.
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