An energy efficient system for controlling the environment in a greenhouse. The system includes an infrared heater, having a burner, a heat disbursement means and an exhaust means, and a layer of reflective and insulative material selectively deployable below the roof and inside the walls of the greenhouse to retain heat within the greenhouse, to prevent excess heat from the sun from entering the greenhouse and to reflect light into the greenhouse from the sun. The system also includes an air-to-water heat exchanger, connected at the exhaust end of the heater, that transfers heat from the heater's exhaust to water used in the greenhouse. The heated water is stored in an underground tank. A series of connected pipes, in communication with the tank, are set into the floor of the greenhouse to circulate the water through the floor to remove excess heat from the water.