A refrigerant system includes a controller that enables the system to dehumidify the air in a room without relying on a humidistat and without having to operate the system's compressor and electric heater at the same time. To dehumidify the air, the system's compressor, supply air fan, and outside air damper are controlled in a manner similar to other systems operating in a cooling mode when the room temperature is above a certain setpoint temperature. When the room temperature falls below the setpoint, however, the operation changes significantly. The controller closes the outside air damper, decreases the speed of the fan, and continues operating in this manner until the room temperature decreases to a subcooling temperature limit. The subcooling temperature limit is less than a predetermined limit that is used during the system's normal cooling mode.