Studies of commissioning projects in existing buildings show median paybacks of 1.1 years and savings of up to 30%, sometimes more. Commissioning is a process to ensure building performance problems are understood and corrected. Deficiencies such as design fl aws, construction defects, malfunctioning equipment, and deferred maintenance have a multitude of consequences, ranging from eq uipme nt failure, to poor indoor air quality and comfort, to unnecessarily high energy use or under-performance of energy efficien cy strat egies. Fortunately, an emerging form of quality assurance, known as building commissioning, can identify and cure most de ficiencies. This course will explain the purpose of a commissioning process, and discuss the impact of the commissioning process on energy efficiency.