In a method for controlling the temperature of a room with a flat heating system, in particular a floor heating (1), a main flow pipe is connected-heating water-(3) and a main-heating water-return line (2) via distribution means with the individual rooms of an appartment or space group. Each admixture circuit is associated with a space, the is formed in such a way that the space-flat heating system (1) of the main heating water-feed line (3) a controllable amount of the supplied heating water from the space-flat heating system back flowing colder return water can be admixed with, so as to maintain the temperature of the into the radiant heating system is offset (1) in-flowing water at a desired value, wherein the said radiant heating system (1) permanently of water flowing through a circulation pump (26) at a substantially constant amount in circulation.