We developed a simulation-based approach for fault impactanalysis for a single duct variable air volume (VAV)system, and analyzed the dynamic and steady-state impactof equipment physical faults on building operation.The simulation model, a virtual testbed, can capture physicalfaults in the HVAC system of a large commercialbuilding. The model can be used to generate data thatcan then be analyzed to quantify the impact of single ormultiple faults. This paper illustrates the implementationof three physical faults: supply air temperature sensorbias, outdoor air temperature sensor bias, and coolingcoil valve stuck. Each fault was simulated with severalfault intensity levels and under different seasonal operatingconditions. Then, we analyzed the impact of theabove-mentioned faults using the energy and comfort metrics.The results show that the impact of a given physicalfault depends on implemented control logic sequence andthe seasonal operating conditions.