A filter unit heat exchanger is provided that may include a housing substantially surrounding a heat exchange assembly. Provided through the housing are one or more tortuous fluid flow paths used to direct airflow therethrough around portions of the heat exchange assembly for efficient operation. The tortuous path(s) may be provided by one or more nozzle openings on an input side of the housing and one or more diffuser openings on an output side of the housing, where the nozzle openings and diffuser openings are offset to cause desired airflow deflection. The filter unit may include desired symmetries to improve manufacturability and/or installation.