HVAC-Cx is a software tool designed to facilitate performance analysis for mechanical equipment buildings. It is used for ongoing monitoring and provides the ability to detect faults related to improper operation, using expert rules to present results of the most likely fault causes and to assist in documenting results. The goal is to optimize the system performance in terms of occupant comfort, energy management and equipment life. It was conceived exclusively for tertiary buildings equipped with one (or several) AHUs, terminal units, chiller loops, and chillers. The commissioning methods developed can be applied to several types of equipment and custom rules can be introduced. The structure includes future expansion capabilities for the analysis of chillers.