The requirements for modern structures to ensure the energy efficiency of buildings must be implemented through an accurate diagnosis of the situation before the actual modernization of the building. This paper describes the benefits of non-destructive thermal testing for evaluating building performance and designing accurate energy retrofit projects for the residential sector. Infrared diagnostics allows you to quickly and accurately assess the performance of building en-velopes, identify areas where high heat losses are observed for their subsequent elimination. This article presents the technical features of thermal imaging of the building envelope of a block-modular multi-apartment residential building. To prioritize building modernization measures, thermal imaging identifies areas of high heat loss and low insulation efficiency. Based on the rel-evance and practical significance of building thermography when considering issues of energy saving and energy efficiency, the authors presented some features and results of external and in-ternal thermography using the example of a dwelling in an apartment building.