The aim of this study was to examine the parameters affecting energy consumption and indoor air quality in university buildings and to develop methods to improve these issues. Izmir was chosen as the target region for the research. Within the scope of the study, examinations were carried out in the selected classes in two different buildings of Yaşar University. In these classes, indoor air temperature, CO2 concentration, and window opening data were measured and recorded at 15-minute intervals for 1 year. In addition, during the measurement process, the energy consumption data of buildings, operation conditions of the HVAC system, and occupancy data of the classes were collected. Analyses were made about the change of CO2 concentration for the use of the measurement data collected during the lessons and exam periods. In these analyses, the effect of occupancy and window opening on the CO2 concentration and indoor air temperature were investigated. A volume flow rate has been proposed in order for the CO2 concentration to not exceed accepted levels, which should be 1000 ppm according to ASHRAE standards. In addition, the effect of outdoor air temperature and HVAC operating conditions on energy consumption was studied.