Heating, ventilating, and air-conditioning (HVAC) systems are designed to ensure acceptable indoor thermal conditions and quality. They consume a major portion of the energy delivered to buildings and therefore they have been identified as a potential candidate for improving the energy efficiency of air-conditioned buildings. In this study energy savings and comfort enhancement are identified with new HVAC operation strategies for a shopping mall in the hot-humid climate of Saudi Arabia. The energy simulation program VisuaIDOE 4.0 was used to perform the HVAC and control simulations. Various zero-investment strategies such as thermostat control, night setback control, time-scheduled operation, etc. are investigated. The Simulation model was first calibrated with actual consumption values to ensure an accurate and realistic retrofit simulation. The study indicates that it is possible to achieve substantial energy savings while maintaining thermal comfort with the implementation of new HVAC operation strategies. Copyright (C) 2009 John Wiley & Sons, Ltd.