Ongoing and Retro-Commissioning
Ongoing commissioning (OCx) is a continuous process that uses trend data, monitoring, and periodic review to sustain performance after initial commissioning. Retro-commissioning (RCx) applies a commissioning-like process to an existing building that was not originally commissioned, typically to resolve operational problems and capture energy savings.
RCx phases mirror new-building Cx: planning and scoping, investigation (document review, site survey, trend analysis, interviews), master list of findings, implementation of low-cost and capital measures, and persistence/handoff. The candidate must know RCx focuses first on no-cost and low-cost operational improvements before capital measures. Common traps: (1) confusing RCx with an energy audit - RCx emphasizes functional performance and operational correction; (2) skipping the investigation phase and jumping to fixes; (3) failing to establish a baseline for measuring persistence; (4) ignoring occupant complaints as a data source.
Key tools include trend logging, building automation system point review, schedule and setpoint verification, and benchmarking. Persistence requires documenting measures, updating sequences, training staff, and setting up ongoing monitoring.
Rule of thumb: in RCx, verify schedules and setpoints before recommending equipment replacement - many savings come from corrected controls. Worked example: trend data show an air handler running 24/7 despite occupancy from 8 a.m. to 6 p.m.; correcting the schedule is a no-cost measure with measurable savings, tracked against the pre-correction baseline.