Abstract: A heat exchange system for recycling waste heat, such as that leaving a building stack or flue, to supply heat where needed, such as to incoming fresh air or to tempered stored water of the building water storage system, wherein the building has a source of heat at a constant temperature (such as a furnace, a cooking facility, or a washing facility), from which waste heat is involved in the materials to be conveyed therefrom for discharge from the building, in which a closed circuit heat generated refrigerant flow type refrigeration system is established including a heat recovery coil in heat exchange relation to the waste heat, a heat discharge coil in heat transfer relation to the fluid to be heated at a level above that of the heat recovery coil, and a refrigerant receiver at a level adjacent the level of the heat recovery coil, with the system being charged with a halogenated hydrocarbon type refrigerant to bring the liquid level of the charge within the receiver above the level of the heat recovery coil