RCx, CCx, MBCx - What's the Difference?

You say potato, I say potato . . . With so many types of “commissioning” being tossed around, you couldn’t be faulted for being slightly confused. Here are the definitions for the various commissioning options:

New construction commissioning

Commissioning is a systematic process of ensuring that all building systems perform interactively according to the design intent and the Owner’s operational needs. The process evaluates building equipment, subsystems, operation and maintenance (O&M) procedures, and performance of all building components to ensure that they function efficiently, and as designed, as a system. Single instance commissioning typically occurs with a newly-constructed building or major building addition and is applied from project inception to initial occupancy.

Retrocommissioning (RCx)

Single-instance commissioning of systems in an existing building. This may be needed when buildings are adapted, additions are made, and/or considerable time has passed. It may resolve problems that occurred during design or constructions and bring the building back to its original or desired performance.

  • A one-time event
  • The building has not been previously commissioned
  • May or may not adhere to building’s original design intent
  • Utilizes diagnostic monitoring and functional performance tests

Periodic commissioning of systems in an existing building to ensure that systems are operating as intended. Ideally recommissioning is planned for in the original commissioning of the building, or when it is retro-commissioned.

  • A one-time, periodic, or occasional event
  • The building has been previously commissioned
  • Adheres to building’s original design intent
  • Utilizes previously developed functional performance tests

Retro-commissioning and recommissioning are basically the same procedure. The main difference is that the term “recommissioning” is used when the building has been commissioned previously, therefore the process tends to be faster and simpler as a result.

Continuous Commissioning (CCx)

“An ongoing process to resolve operating problems, improve comfort, optimize energy use, and identify retrofits for existing commercial and institutional buildings and central plant facilities.” Texas A&M University.

  • Continuous monitoring with assessments performed at least quarterly
  • The building may or may not have been previously commissioned
  • Does not adhere to building’s original design intent – is concerned instead with trending relative to a baseline and optimizing performance to meet current requirements
  • Utilizes building automation system and/or metered energy trend data and/or condition acceptance tests
Monitoring-Based Commissioning (MBCx)

An approach that involves three elements: Energy information systems/ building diagnostics, retro-commissioning and ongoing commissioning and measurement-based savings accounting using the metered and monitored data.

So, which solution is right for your facility? Our RCx/CCx/MBCx Team can help you understand the options and benefits for each pathway. Please reach out for a consultation.


  • U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. July 2014 “Commissioning of Federal Facilities.”
  • Schneider Electric “Commissioning for Energy Efficiency.”