Recommissioning refers to the systematic process of analyzing an existing building’s mechanical systems, controls, and equipment with the goal of ensuring that they are operating optimally and efficiently for the building’s current use. Among other measures, the process may involve adjusting, tuning, modifying, or repairing building equipment and control systems.

Even buildings fully commissioned when built will experience changes in operating behavior and efficiency in just a few years. Some buildings are negatively affected by unresolved system deficiencies that date back to construction. Modern HVAC systems can be complex, and small changes in equipment operation, sensor accuracy, control setpoints or system overrides can have compound effects on system operating behavior which may diminish performance and energy efficiency.