There is a growing consensus that most buildings do not perform as well as intended and that faults in HVAC systems are widespread in commercial buildings. An automated fault detection and diagnosis tool for HVAC systems is being developed, based on an integrated, life-cycle, approach to commissioning and performance monitoring. The tool uses component-level HVAC equipment models implemented in the SPARK equation-based simulation environment. The models are configured using design information and component manufacturers' data and then fine-tuned to match the actual performance of the equipment by using data measured during functional tests of the sort using in commissioning. This seminar presents the architect of the tool and the results of field tests on mixing box and VAV fan system models in an experimental facility and a commercial office building.