The object to be tested is a block of flats located in Volgograd (Russia, N 48°). Design insulation of doublelayer wall structures made of AAC with exterior coating in the form of brick masonry can ensure minimum allowed element-by-element requirements for heat protection according to the Russian Construction Norms and Regulations (SP 50.13330.2012) provided the requirements for specific heat consumption for heating and ventilation in the building are met. In most cases double-layer exterior walls without extra insulation do not correspond to basic level of heat protection and almost do not have heat and energy reserved. An actual energysaving class of the building in operation is significantly lower than the one stated in the design project. The deviation of actual heat protection for heating and ventilation in the building from the estimated value can reach more than 75%. With the aim to ensure actual energy-saving effect it is necessary to improve the model taken as a basis to determine estimated heat consumption for heating and ventilation in the building according to the Russian Construction Norms and Regulations (SP 50.13330.2012), and to ensue whether the actual design solution is performed correctly. Specific heat protection in the building shall be estimated with due account for edge zones of building envelopes based on 3-D temperature fields data. Only certified construction materials and structures can be used in construction. Extra insulation at points of HDD 20/8 >= 4200 K*day/year is recommended to minimize heat and power and energy risks and to improve heat protection of exterior walls made of AAC blocks. It is recommended to perform control over the quality of design and construction under state expertise of the projects and state construction supervision.