A method and apparatus are disclosed for controlling dehumidification of an airflow to be conditioned for supply to a climate controlled space. The airflow to be conditioned is passed over a plurality of refrigerant conveying conduits of an evaporator of a refrigerant vapor compression thereby cooling the airflow. A controller operates the refrigeration vapor compression system to maintain the airflow at a set point air temperature indicative of a desired temperature within the climate controlled space. The controller also adjusts an evaporator expansion device for controlling the flow of refrigerant through the evaporator so as to reduce the temperature of the refrigerant within the refrigerant conveying conduits of the evaporator whenever further dehumidification of the air flow to be conditioned is desired.