What is Retro-Commissioning?

Retro-commissioning, (RCx), is a detailed look at how well heating, ventilation, and air conditioning (HVAC) and lighting controls are working. The process involves identifying and correcting deficient building sub-systems and controls in existing buildings. Retro-commissioning identifies drifts from normal performance and fine-tunes those systems, bringing them back to their intended level of performance. The energy conservation measures (ECMs) uncovered during retro-commissioning typically involve reprogramming controls, repairing dusty dampers, and replacing faulty actuators, valves, variable speed drives and sensors. A thorough look is also taken at how building operators are using the controls, since poor operational procedures usually lead to energy waste. Retro-commissioning typically includes an energy audit of the entire building including a study of past utility bills and a series of interviews with the facility personnel. Diagnostic monitoring and functional tests of building systems are then executed and analyzed using extensive data logging. Although retro-commissioning is usually more expensive and intensive than an energy audit, it typically yields better savings due to the fact that the payback is often less than 2 years.  

Along with the energy audit, retro-commissioning must also be conducted and included in the Energy Efficiency Report for Local Law 87 compliance. Local Law 87 retro-commissioning of building base systems involves diagnostic monitoring, functional upgrading, and repairing of defects in existing systems. The goal is to optimize the performance of existing controls, sensors, valves, and systems without the reliance of complete replacement. Energy audits may result in the identification of complex problems in a building’s optimal functionality; retro-commissioning is the process that strives to amend these issues. Similarly with energy audits, retro-commissioning must be completed by a certified agent. Under Local Law 87, the retro-commissioning report must include information regarding the project team, building data, testing protocol, master list of findings, and catalogue of deficiencies corrected. The law also mandates that building owners conduct retro-commissioning no more than 4 years prior to the date that the Energy Efficiency Report is filed with the Department of Buildings. Certain properties are exempt from the retro-commissioning requirement, including LEED-certified Existing Buildings that earn a point for Existing Building Commissioning within two years of an Energy Efficiency Report.