Disclosed is an air heating apparatus including a burner configured to cause a combustion reaction, a main passage, through which water flows while circulating, a heat exchanging device configured to receive heat from combustion gas generated by the combustion reaction and heat the water flowing along the main passage, a heating heat exchanger configured to receive the water heated by the heat exchanging device and exchange heat with the air for heating, a fan configured to send the air to the heating heat exchanger, and a hot water discharge port connected to the main passage such that the water heated by the heat exchanging device is discharged to an outside of the main passage.

The invention concerns a system and method for energy and hydrometric control of a horticultural greenhouse. The present invention proposes a perfect and complementary arrangement of various energy sources while optimizing them. The use of fossil energy is significantly reduced, making it possible to achieve carbon neutrality, whatever the season and/or climate, and external CO.sub.2 becomes a usable and manageable source of fertilizer. In particular, the invention optimizes the use of heat pumps and other energy sources, preferably alternative energy sources such as hydraulic, wind, solar, geothermal, biofuel or a mixture of these.