Abstract: Room heat exchangers of varying priority are provided by setting the volumetric flow rate of a medium by means of the room heat exchangers of a heating or cooling system. A target spread of the flow and return temperatures for each individual room heat exchanger(s) is set by fixably or adjustably limiting the respective room heat exchanger valve(s). A system-specific target spread for high-priority room heat exchangers is a basis to allow a lower target spread and a higher target spread is ensured given low-priority room heat exchangers. When operating in a high-priority room heat exchanger with a lower spread, the volumetric flow through at least one low-priority room heat exchanger with a higher spread is changed in such a way that a return temperature optimized for the heating device of the heating system is set by mixing the return medium from all room heat exchangers of the heating system.