A transportation refrigeration unit (24) to provide a flow of supply air to a selected space includes a compressor to compress a flow of refrigerant and an engine (36) powered by a flow of fuel and operably connected to the compressor to drive the compressor. An evaporator circulates the flow of refrigerant therethrough to cool the supply air and includes a substantially unitary evaporator housing (50) having a supply air inlet opening (52) and a supply air outlet opening (56). An evaporator coil (32) is located in the evaporator housing, the flow of refrigerant circulating across the evaporator coil. An evaporator fan (34) is located in the evaporator housing to urge the supply airflow into the evaporator housing via the supply air inlet opening (52), across the evaporator coil (32) and out of the evaporator housing through the supply air outlet opening (56). The evaporator fan (34) can be located upstream or downstream of the evaporator coil (32).