Commissioning (Cx), Recommissioning (RCx), OCx: Stop Confusing These Terms

The commissioning vocabulary in our industry is genuinely confusing. Owners ask for “commissioning” when they mean retro-commissioning. Engineers spec “recommissioning” when they mean ongoing commissioning. The terms get used as if they’re the same. Meanwhile, the building isn’t operating the way it was designed to.

Here’s the clean version, as ASHRAE Guideline 0 and the California Energy Commission’s technical references generally define it.

Commissioning (Cx)

This is the original new-construction process, the automation system is installed, functionally tested, documented, and turned over to the operations team with training. This is also largely what Title 24 acceptance testing covers. It happens once, at the front end of an asset’s life.

Retro-commissioning (RCx)

This applies to an existing building that was never properly commissioned, or whose commissioning records are lost.

RCx is forensic. The team starts with site investigation. What was the design intent? What’s the current operating state? Where are the gaps?

Typical findings on a building that hasn’t been touched in 15 years:

• Economizers stuck closed
• Simultaneous heating and cooling
• Schedules running 24/7 because no one updated them post-COVID
• Setpoint creep where every occupant complaint resulted in a static override

Typical RCx savings on a commercial building: 5–15% of HVAC energy. Simple payback is usually 1–3 years.

Recommissioning

This applies to a building that was properly commissioned at construction, but has drifted, and the original commissioning documents still exist.

The team’s job is to compare current operations against the documented design intent. Then bring the system back into alignment. As a result, recommissioning is more efficient than RCx because the baseline documentation already exists.

Ongoing commissioning (OCx) or monitoring-based commissioning (MBCx)

This is a continuous process rather than a one-time exercise. The building has analytics or FDD software that monitors operations continuously. It flags deviations and feeds a structured response process.

OCx is the answer to the question “how do we prevent drift in the first place.” Increasingly it’s becoming the standard for large institutional portfolios. The reason: the savings are sustained rather than reset every few years. See our FDD post for how the analytics layer fits in.

Which one do you need?

Some honest questions:

• Do you have commissioning records from the original construction? If no — retro-commissioning. If yes — recommissioning.
• When was the last time the building’s sequences of operations were verified against current operation? If more than 5 years — RCx or recommissioning is overdue. If you don’t know — same answer.
• Do you have continuous trend data on the air handlers, central plant, and major energy meters? If no, you have no way to detect drift between commissioning events.
• Is the building part of an institutional portfolio? Portfolio-level OCx is dramatically more cost-effective than individual building RCx cycles.

Where Signet fits

We perform RCx, recommissioning, and OCx across our service portfolio. Typically we anchor on Niagara analytics or partner FDD platforms layered over our existing BAS deployments. The biggest single piece of advice we give clients: the first RCx project is the easy win. However, the second RCx project, three years later, finds 70% of the same problems. The way out is continuous monitoring, not periodic re-discovery. See our Service & Support tiers for how ongoing programs work.

Talk to Signet Controls. Planning a BAS install, retrofit, integration, or service contract in California? We work across Los Angeles, Orange County, the Inland Empire, the Central Coast, and Kern County. Reach our team at info@signetcontrols.com or call (877) 874-4638.