This article discusses the problems of calculating heat losses through various corners of the outer walls of buildings with effective thermal insulation. An overview of three methods for calculating heat losses for these enclosing structures is made. The calculation of heat losses of three corner rooms of fundamentally different sizes was carried out according to the methods considered. The limits of using the calculation for specific heat loss are considered. The results of numerical modeling of heat losses through the corner enclosing structures are shown. The dependence of specific heat losses through the corners of the premises of the considered enclosing structures on the angle was revealed. © 2023 Author(s).