The article describes an approximate analytical method for calculating the humidity regime of multi-layer building enclosing structures. The novelty of the proposed method consists in using an analytical dependence to determine the position of the possible condensation plane obtained as a result of the study of the function representing the difference between the partial pressure of water vapor in the considered section of the enclosure structure and the partial pressure of saturated water vapor at the extremum. The results of calculating the humidity regime of the external wall of a residential building under construction in the city of Samara, using a monolithic bespeschany expanded clay concrete with a density equal to 600 kg/m3, are presented. The assessment of moisture accumulation in the considered external wall both for the annual period of operation of the building, and for the period of months with negative temperatures, showed compliance with the regulatory requirements for heated rooms

Keywords: enclosing structure, humidity mode, moisture transfer, vapor penetration resistance, water vapor, condensation plane