Abstract: A heat pump system for conditioning outside air supplied to a building is provided. The system includes a pre-processing module that receives and cools air when the system is operating in a summer mode. A supply air heat exchanger is in flow communication with the pre-processing module. The supply air heat exchanger receives and cools air from the pre-processing module in the summer mode. A processing module is in flow communication with the supply air heat exchanger. The processing module receives and dehumidifies saturated air from the supply air heat exchanger in the summer mode.