Funded by a Butler University Innovation Fund Grant, the $50,000 greenhouse prototype was created because of a building code issue.
The powder-coated steel tube frame is wrapped with a 2×2 fiberglass furring system. The skin a is double-wall polycarbonate panel. Windows are operational, connected to heat-sensitive sensors that require zero energy.
The unit does feature heating and air-conditioning. Fans operate on a thermostat. The greenhouse “plugs into an exterior port like an RV would,” Gray details, expressing measured concern about the power cost. “Butler provides the power, and because it’s an educational project, it’s not our primary concern. The requirement of growing year-round trumps efficiency.”
Besides, he adds, it’s a trade-off: passive ventilation should allow them to run without air conditioning or heat most of the year. However, Gray acknowledges that heating the greenhouse will be a challenge in the dead of winter.
Dorsey points out that winter temperatures will impact the greenhouse more significantly because it’s elevated, allowing cold air to circulate underneath the structure. However, they situated it to maximize the angle of the February sun in order to take advantage of as much passive solar heat as possible. Ultimately, though, he says the plan is to extend the growing season, but not use the greenhouse all winter.