Air recirculation in ventilation systems is essentially the mixing of a certain amount of exhaust air into the supply air. This process provides a reduction in energy consumption when heating fresh air in the winter season.
Heat recovery in ventilation is a method of transferring heat energy from the exhaust airstream to the supply airstream. Heat recovery is used when there is a temperature difference between the extract air and the supply air in order to increase the fresh air temperature. This process does not imply the mixing of airstreams, and the process of heat transfer takes place through any material.