Strongly influenced by the need for energy efficiency improvements, this research aims to help reduce energy consumption by applying effective energy measures. Improvements in a building's energy efficiency bear the greatest potential in terms of saving energy and reducing toxic gases emission. Three energy improvement measures have been suggested concerning "Karaburma" Elderly Care Facility in Belgrade: (1) the insulation of a thermal envelope, (2) the replacement of old coal boilers by new pellet boilers, and (3) the replacement of windows and doors. The object is a complex of nine blocks of buildings built in 1963. The analysis of the energy characteristics of this object has been carried out by applying mathematical modeling. The saved energy is able to pay back the investments within 11 years and 3 months, while simultaneously having a positive effect on the environment since coal is discarded as a fuel. The goal of this engineering and economic analysis is to influence some important future decisions regarding the systematic improvement and reconstruction of the existing buildings in order to permanently reduce energy expenditure and CO2 emission. Rather than depriving the consumers in any way, energy saving benefits the environment, life quality, and competitiveness of the facility. (C) 2015 Elsevier B.V. All rights reserved.