Use a small fan to inflate the space between the two layers of film plastic on the roof. Because moisture reduces the amount of light able to enter the greenhouse, inflate the space between the plastic layers with the cooler, dryer outside air rather than the warm, moist inside air, which can cause condensation. The two layers of film plastic with air separation provide insulation and roughly 30-percent energy savings over a single layer of film plastic. The Quonset hoops can go directly into the ground or there can be short sidewalls. Pipes set into the ground serve as the foundation and anchor the building against wind.
Sidewalls permit the installation of rollup devices so the sides can be opened for ventilation.
This manual system is useful in the spring for continuous ventilation during the day. Environmental Control System Proper temperature and humidity conditions are required in a greenhouse for good germination and growth of transplants. These conditions are best controlled with an automatic environmental control system in the greenhouse. Because winter's lowest temperatures may occur during the transplant production season and high temperatures may occur in early spring, the equipment needed for an environmental control system should be sized for year-round conditions. Do not take short cuts on the environmental equipment.