Abstract: A building is heated using an infrared heater with a radiant tube. A heated gas is fed to the radiant tube at a first end and the tube is further fluidically connected at its second end to a heat exchanger. A portion of the thermal energy contained in the heated gas is conveyed to a buffer storage tank, from which the energy can be removed in particular to heat up industrial water or to heat a second part of a building thermally isolated from the first building, or a second building. There is also provided a solar collector. The feed and/or return of the heat exchanger and/or the feed and/or return of the buffer storage tank can be fluidically connected to the feed and/or return of a thermal solar collector via pipes and switchable valves.