The object of the study is an underground structure located in a region with a harsh climate. The placement of structures in the underground space solves the urgent problem of reducing the heating cost for buildings and structures in the northern regions. The paper proposes ways to improve the energy efficiency of underground structures through the choice of the structural characteristics of such structures by the criterion of minimum heat loss. The method for calculating heat energy losses through external enclosing structures is based on determining the temperature fields in the ground mass adjacent to the structure throughout the year. The temperature in the ground is determined by solving the non-stationary heat conduction problem. The results of the step-by-step solution of the heat transfer problem in the form of temperature fields are used further to calculate heat losses at specified time intervals. The results of determination of the influence of thermal insulation, the depth of the object relative to the ground surface and the temperature of the internal air on heat loss are presented. The analysis of the presented results makes it possible to make the correct choice of the design parameters of the designed underground facilities in various climatic conditions.