Systems and methods for dehumidifying or drying air entering a greenhouse while it is being cooled are disclosed. Air to be cooled is drawn through a cooling medium (13), and the systems and methods make use of heat extracted from the hot air before entering the cooling mechanism for use in heating the cooled air exiting the cooling mechanism. This reinsertion of the extracted heat into the exiting air allows for humidity control while maintaining a lower temperature compared to the temperature of the air as it entered the cooling mechanism. Different embodiments according to the present invention comprise closed-loop, energy neutral air drying systems that do not utilize external energy or materials to dry the air. This provides an energy efficient air drying system that allows for greenhouse operation with reduced operating costs.
