Existing Building Commissioning (EBCx) is a systematic process for planning, assessing, investigating, analyzing, improving, optimizing and verifying the performance of building systems and assemblies.Commercial buildings account for almost half of the total energy use and consume one billion gallons of fresh water a day in the United States. Over time, even well commissioned buildings lose their efficiency. Re-commissioning, Retro-commissioning, ongoing commissioning and continuous commissioning are a crucial step in maintaining and reducing the energy consumption of the building.