Retro-commissioning (RCx) is the process of tuning systems in existing buildings so they operate to the owner’s operational needs. A key piece of the RCx process is compiling, understanding, and acting upon the vast amounts of data available. The speakers will discuss how data analytics can be used to improve the RCx process and result in larger energy savings. By using readily available data visualization tools, building operation can be more clearly diagnosed, and the process more clearly communicated to owners and facilities staff.