The paper presents an approach in the determination of the most economically efficient building from the viewpoint of the costs of envelope's composition, the present value of heating costs and the costs incurred in fitting out the boiler room (hereinafter: the costs of the boiler room). The process of determination starts with the selection of a certain building in the phase of project engineering, next different combinations of envelope composition are numerically analysed and finally the optimal solution or approximation of that solution is defined on the basis of the analysed results. The approach is presented on the simulation case of a single-storey house. The result of the study is presented by a set of parameters showing different costs of building envelope from the point of initial investment for a selected energy demand of building. In the second step we calculated the present value costs of heating and compared them with the additional cost of initial investment in the envelope and additional investment in the building's boiler room in order to determine which combination of envelope and heating system is the most economically efficient (C) 2014 Elsevier Ltd. All rights reserved.