An analytical dependence is presented for calculating the power of a heating system, taking into account the aerodynamics of the movement of air flows inside a heated room. The analytical dependence is derived on the basis of the theory of a two-zone mathematical model of a heated room. The method allows us to determine a rational way of organizing heating to ensure minimal transmission heat loss through enclosing structures, taking into account factors affecting thermal and air processes in a heated room and contributing to a decrease in the power of the heating system as a whole. The results of the analysis carried out on the regularity of the movement of air flows in a room divided into two control volumes (CV): upper and lower CV. A mathematical model of the processes of heat and mass transfer of a heated room in an administrative or residential building has been developed, which takes into account the heat exchange between the upper and lower CV. The physical picture of the distribution of air and heat flows in a heated room with a local heat source located in the window sill space of the heated room is analyzed. A method for calculating the power of the heating system is proposed, taking into account the nature of the aerodynamics of the distribution of air flows in a heated room. An analytical dependence for calculating the thermal power of a heating system is presented, taking into account the characteristics of the distribution of heat and air flows across two control volumes of the heated room.