The present disclosure provides methods and systems for regulating the room temperature in a room or in a plurality of rooms, the room temperature can be regulated by regulating the mass flow of a heat-carrying fluid flowing through a heat exchanger according to a determined current room temperature. In accordance with some embodiments, a temperature sensor in the room can be dispensed that can determine the current room temperature, in each case the mass flow of the heat carrying fluid through the heat exchanger and the flow temperature prevailing at the input to the heat exchanger and the return temperature prevailing at the output of the heat exchanger are measured, and that a temperature assigned to the determined values of the mass flow, the flow temperature and the return temperature is output as the current room temperature and used for regulation.