Building energy management system (BEMS) integrated in building is of great importance in modern nearly zero energy buildings (nZEB). Nearly zero energy standard describes energy efficiency concept with energy conservation and energy savings. In this work, an upgrade of the BEMS with goal of reduction of cooling energy demand for the building of the Mechanical Engineering Faculty in Slavonski Brod, object in Ivana Gundulića Street is proposed. BEMS controls ventilation system of below roof/attic area. Described technical solution is designed inside RESCUE IPA CBC project (Faculty of Technical Science Novi Sad, Faculty of Electrical Engineering, Computer Science and Information Technology Osijek).