Systems and methods for changing the relative humidity of or drying air entering a greenhouse while it is being cooled are disclosed. Air to be cooled (11) is drawn through a cooling mechanism (13). The system than transfers the heat extracted from the hot air for use in heating the cooled air exiting (12) the cooling mechanism. Heat transfer uses peat pipes (14). 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.
