A large office building system located in Gaithersburg, MD, was simulated using the HVACSIM + computer program. A typical floor of this 11-story building was selected and divided into four zones, with one airhandling unit serving each zone. Dynamic interactions between the building zones and the HVAC and control system were studied for several different control strategies during the cooling season. Simulations were performed using the building shell and zone models along with the air handler and control system models. Simulation results are presented and compared with experimental measurements. The effects of three different control schemes on energy consumption are compared with each other. These schemes are: the start/stop control without purging cycle, the start/stop control with purging, and continuous operation.