S1-ERV160 & ERV220 Energy Recovery Ventilators from York removes stale air unhealthy air and replaces it with a stream of fresh air. Both incoming and outgoing air streams pass through an energy transfer core where both heat and moisture from the exhaust air are efficiently transfered to the incoming air. An air duct system supplies the fresh air brought in by the ERV and distributes it throughout your home. Another duct draws the existing stale air back to the ERV and then exhausts it outdoors.