Modeling of the heat-air regime in the main body of the TPP in the scientific and technical literature is given insufficient attention. To simulate the heat-air regime in the main building of a thermal power plant, it is necessary to develop a geometric model of the boiler-turbine shop. A mathematical model of the heat-air regime in the main building of the TPP will allow us to develop energy-saving measures and improve the microclimate in the premises of the plant. The study has been carried out using mathematical modeling methods based on the DesignModeler graphic editor in ANSYS software. A geometric model of the boiler-turbine shop of Ivanovo combined heat and power plant-2 (CHPP-2) has been developed. It allows us to develop a mathematical model of heat and mass transfer in the air space of the main building of the plant. The three-dimensional geometric model of Ivanovo CHPP-2 is the first stage of the development of an integrated mathematical model of the heat-air regime of the main building. Its aim is to evaluate measures that reduce consumption of thermal and electrical energy for the in-house needs.