## 4 Results and Discussion  
The consumption of thermal energy for the analyzed buildings for the needs of central heating in the years 2001-2019 is shown in Figures 2-4. The amount of consumption was expressed using unit indicators of final energy demand, covers the periods before modernization, after thermal improvement (reference year) and the period after the introduction weather controlled central heating system (Egain). Figure 3: Thermal energy consumption for central heating in the years 2001-2019 in building B.  
Figure 2: Thermal energy consumption for central heating in the years 2001-2019 in building A. In the years 2011-2014, the buildings were thermomodernized by insulating the walls. After the thermal improvement (without modernization of the heating system), energy consumption was reduced, which is shown in Table 5.  
The thermal improvement of the external partitions has had the best effect in buildings A and B, where energy consumption has been reduced by about 22-25%. In building C, thermal modernization of the walls did not bring much savings, because only about 7%. The next stage of the research was to check whether the application of the change in the method of central heating regulation from the traditional one, taking into account only the change in the outside temperature to the weather control, will increase the energy efficiency (savings in energy consumption) of the buildings covered by the analysis. For this purpose, the amount of energy consumption reduction \(\Delta FE_{ES,b,i}\) and energy savings \(FE_{\%,ES,b,i}\) were calculated. The calculations were made, for each (full) year after installation of the Egain control system according to formulas 4 and 5. Then the average values of the energy savings obtained were calculated. The results of the calculations are summarized in Table 6.  
Figure 4: Thermal energy consumption for central heating in the years 2001–2019 in building C. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{\(FE_{\%,ES,a}\)} & \multicolumn{3}{c}{**Building**} \\ \cline{2-4}  & **A** & **B** & **C** \\ \hline savings achieved, \% & 22,5 & 25,4 & 7,4 \\ \hline \end{tabular}
\end{table} 
Table 5: Energy savings achieved through thermal improvement of buildings. Analyzing the results contained in Table 6, it can be concluded that the change of the method of central heating control from the traditional one, taking into account only the external temperature variation to the weather control, has resulted in increased energy efficiency in the analyzed buildings. The energy consumption in comparison with the reference year (after the partitions have been insulated) has decreased on average from 12.6 to 30.9 kWh-m\({}^{-2}\)-year\({}^{-1}\). The energy savings are about 16% to 32%. Comparing the savings associated with the introduction of a new control system for central heating installations for individual buildings in relation to the savings obtained as a result of insulating the walls, it can be concluded that in the case of building C, there is a supposition that only a 7% reduction in energy consumption after insulating the walls (where from the theoretical calculations should be about 20% [9]), could be caused by faulty operation of the central heating control system. After changing the control system to a forecast, there was a significant reduction in energy consumption, which in 2015 and 2019 reached almost 40%. Taking into account the above observations when estimating energy efficiency, it was decided to refer to buildings A and B, where as a result of thermomodernization the obtained savings levels are similar and amount to 22% to 25%. These buildings, after thermal improvement, were characterized by similar energy consumption rates in the reference year, which amounted to 74-77,6 kWh-m\({}^{-2}\)-year\({}^{-1}\). In these buildings, the change of regulation method resulted in average reduction of energy consumption in the range of 12,6 kWh-m\({}^{-2}\)-year\({}^{-1}\) (building B) to 17,5 kWh-m\({}^{-2}\)-year\({}^{-1}\) (building A).