In connection with the growing popularity of the reconstruction of old buildings in the center of St. Petersburg as an alternative to the construction of new buildings, there is a need to assess the compliance of existing enclosing structures with modern requirements for heat-transfer. In this work, landmark erected in the beginning of the 20th century is considered. The building of the baths of merchants Tselibeev, located in the historical center of the city, is the object of reconstruction with a change in its functional purpose. For this reason, the work analyzes the enclosing structures and assesses the possibility of their functioning in accordance with modern requirements for heat-transfer in conjunction with the need to preserve the original architectural aspect of the facade, the most significant in the building sequence of Nekrasov Street