Currently, the successful development of construction industry depends on the improved energy performance of buildings, structures and facilities, as well as on the quality assurance of the indoor climate. The approximate calculation of two-dimensional temperature field of the ground outside the underground part of the building is considered using the analytical solution of differential equation of thermal conduction by the method of sources and sinks according to the existing boundary conditions. This problem is a very high-priority task now because of actualization of building standards in Russian Federation and because of the increasing demands to safety and security of heat supply. That’s why it is very important to find a simple but accurate enough dependence for the heat losses through the floor situated on the ground. The results of the estimation of thermal resistance of floor areas on the ground are presented on the basis of the obtained temperature field. The comparison of these results with the regulatory requirements specified in SP 50.13330.2012, and with the data of numerical calculations of other authors using finite difference approximation of the thermal conduction equation with consideration of soil freezing is held. It is shown that the requirements of the SP 50.13330.2012 are physically reasonable, and numerical calculations can also be described by the analytical dependence obtained in this paper with appropriate selection of the numerical coefficients with the preservation of engineering form of the calculation procedure. The obtained model is easy to use in engineering practice especially during preliminary calculations. The presentation is illustrated with numerical and graphical examples.