Method and device for conditioning supply air

A method for conditioning supply air in respect of its temperature in a recuperative heat exchanger (63) through which the supply air and exhaust air flow in heat-exchanging relation comprises supplying water to vertical walls of ex­haust air flow passages (74) of the heat exchanger when cool­ing of the supply air is required and heating the exhaust air by means of a burner (87), preferably a gas burner, immediate­ly adjacent the inlet of the exhaust air flow passages (74) when heating of the supply air is required. A recuperative heat exchanger (63) for carrying the method into effect com­prises means for providing a flowing film of water on the walls defining flow passages (74) for the exhaust air and a burner (87) for heating the exhaust air immediately adjacent the inlet end of these flow passages.