The method is intended for the air-conditioning of spaces which are possibly closed: esplanades of public places, areas for sports and games, buildings, houses etc., but in particular greenhouses for cultivating plants. It is characterised in that a pit 1 is provided below a space, the air of which is to be conditioned, in that this pit 1 is filled with water 4 to constitute a mass, in that there is arranged above the mass of water 4 supports 6, the assembly of which is permeable to air and a part of at least one lower face of which is situated at a height which is sufficient for a volume of air 5 to subsist between the surface of the water 4 and said lower face, in that air is introduced above the water 4 via a duct 9 and a fan 10 at a pressure which is sufficient to cause a diffusion of air directed upwards through the assembly of the supports 6, after modification of the temperature of the air introduced, by thermal action of the mass of water 4. According to circumstances, either the temperature of the air of the space is modified from that of the mass of water 4 or the temperature of the mass of water 4 is modified from that of the air of said space.
