The SABIK heat recovery ventilation units are designed for ventilation of apartments and family houses and are equipped with a plastic counterflow heat exchanger with an efficiency of up to 94%. The SABIK heat recovery units are equipped with two centrifugal fans with economical single-phase EC motors. The SABIK units are equipped with a fully automatic control system with continuous speed control provided by four combined temperature and relative humidity sensors. The design wired controller allows manual fan speed switching, by-pass control, BOOST function activation, automatic operation, night cooling and filter clogging signaling. The SABIK heat recovery units are equipped with G4 filters on the intake and discharge side (optionally with F7 filter on the intake side).