Abstract: A heat exchange system in which sensible and/or latent heat is exchanged between a stream of incoming air into an enclosure and a stream of air leaving the enclosure, comprising a heat exchanger for the incoming air and a heat exchanger for the leaving air, each of said exchangers comprising a group of passages through which the incoming air stream and the leaving air stream, respectively, flow in heat exchange relationship with a liquid passing through a separate group of passages. The liquid is circulated in a closed circuit between the two exchangers in a duct leading from the heat exchanger for the incoming air to the heat exchanger for the leaving air, and, upon heat exchange with the leaving air, recirculated in a separate duct to the heat exchanger for the incoming air.