HVAC systems in buildings must be complemented with a good control scheme to maintain comfort under any load conditions. Efficient HVAC control is often the most costeffective option to improve the energy efficiency of a building. However, HVAC processes are nonlinear, and characteristics change on a seasonal basis so the effect of changing the control strategy is usually difficult to predict.Aim of this thesis is to reduce energy consumptions by defining new HVAC control strategies and tuning control loops in Ozdilek Shopping Center "OSC". To investigate the potential for energy savings and to redefine control scenarios, an energy audit was carried out in "OSC". According to these studies new strategies are implemented by the help of existing building management system "BMS" without making any investment.Performance indices were calculated and compared with the accepted standards. Then normalized performance indices are calculated to reach out a better understanding of the buildings' efficiency.