Energy saving is one of the most important environmental factor during the process of building realization. The optimal selection of machine or machine group for building processes is very important role of building planner during the process of building planning. During this process building planner have to analyse several factors influencing the final effective decision concerning this problem. There are several factors and criteria for effective selection of building machines. In our contribution there are proposed optimizing method and analysed ability of machines to realize designed building process with minimizing of energy consumption (environmental aspect). This method are implemented into two different construction processes: optimal selection of machine groups for soil excavations and optimal selection of the building elevators for vertical transport of building materials during the construction finished processes. Selected scientific methods and theories of problem solution can be divided into these groups: theory of system (creation of building machine selection method), optimizing method (analysis of mechanized building process from the point of minimum energy consumption), queuing theory (application during the mathematical modeling of mechanized soil processes), method of scientific analysis (analysis of factors influencing final decisions), method of scientific synthesis (creation of optimizing method implemented into building processes and possible application in construction sector). The effectiveness of implementation of this method is increased by software support for both model examples. Results of our research work show, that using automated system we can win very quick optimal machine group for defined process and by this way during the process of building planning to increase the effectiveness of building machines selection especially form the point of energy minimization.