Abstract: A regulating arrangement intended for supplying heat to a confined space, including a heating source (13), a regulating means (12) intended for regulated heat supply from the heating source, a device for detecting one or a plurality of measurement values and connected (12a, 12b) to the regulating means, which in dependence on received measurement values regulates the amount of heat delivered by the heating source. The regulating means (12) is controlled (10b) by a device arranged to detect the actual heating requirement of the ventilation air at that moment in time, or for detecting a part of this heat requirement.There is also provided an arrangement or a device for establishing when the requirement to heat an air mass to achieve a pre-determined temperature increase exceeds a pre-determined heating requirement and by how much, by causing the air mass an energy delivering means (4) and establishing the energy taken-up by the air mass and the heat content of the mass at that moment in time.