Night shutter system for greenhouses in cold climates

A night shutter system for greenhouses is described. The system was developed for double glazed quonset type greenhouses with shutter operating in between the glazings. Operation in between the glazings avoids problems due to weather experienced with outside shutters and condensation which can occur using shutters inside the greenhouse. The system is fairly simple to construct and can pay for itself within a year based on energy prices of $9.00/GJ.