Based on numerous analyzes, expertise and energy audits of buildings in the last decade, as well as on the basis of data published by the line ministries responsible for the field of construction and energy sectors, it is evident that the gross final energy consumption in the Building sector in Republic of Serbia is growing. The new and amended EU directives, as well as the legislative framework, imply, in addition to reducing the primary energy used in buildings, the implementation of efficient technical systems that include renewable energy sources (hereinafter referred to as RES), have a minimized impact on the environment (Zero Emission Buildings), as well as positive economic indicators. For these reasons, especially when it comes to newly designed buildings, it is necessary to implement improvements in terms of the 4Es: Energy, Efficiency, Ecology and Economy. The paper gives a proposal of bulding 4E improvement, based on the analisys of different energy sources and technical systems in a newly designed residential building located in Belgrade. Four scenarios with different energy sources, as well as internal installations in the building, which include a heating system and domestic hot water preparation, were analyzed. Energy source types, which are compared are as follows: district heating system that generates heat from fossil fuels, biomass, natural gas and air to water heat pumps, with the calculation of primary energy, CO2 emission and the exploitation cost for each scenario. The results obtained after the conducted analysis indicate the optimal solution.