The analytic research was conducted for a residential building built according to a typical project in Lviv. As the research data showed, the requirements of the existing normative documents of Ukraine do not allow to significantly reduce the heat load on the heat source. Thus, the value of the maximum heat flow to the heating system decreased by 36%, and the maximum heat flow to the hot water supply system - by 7.7%, and the total maximum hourly heat consumption, respectively, decreased by 23%. In addition, studies have established that for such values of the thermal power of the heat source, a decrease in the temperature parameters of the heat carrier can lead to an increase in the consumption of the heat carrier to provide thermal energy to the house by almost 3 times. And this, in turn, for the same diameter of the pipeline, leads to an increase in specific pressure losses by more than 5 times, and, accordingly, to an increase in the power of circulation pumps, the consumption of electrical energy and the cost of these pumps. This means that at present, the transition of large systems of district heating system of Ukraine to low-temperature coolants is possible only during the reconstruction of heat networks.