Project delivery

What is commissioning in construction?

Commissioning (often shortened to Cx) is a quality process that checks and documents that a building's systems, especially mechanical, electrical, controls, and life safety, are installed and perform the way the owner's requirements say they should.

Two construction professionals review paper plans beside a tablet at a jobsite workbench.
Plan reviews connect field conditions, drawings, and the next decisions on a job. AI-generated illustration.

Commissioning answers a simple question: does the building actually work the way the owner asked for? Startup proves a rooftop unit turns on. Commissioning proves it heats, cools, and ventilates the right zones at the right setpoints, talks to the building automation system, and fails safely when a sensor goes bad. ASHRAE Guideline 0 describes the commissioning process as a quality-focused process that runs from predesign through occupancy and operation, verifying and documenting performance against the owner's project requirements.

Commissioning is led by a commissioning authority or commissioning agent (CxA), who may work for the owner, the design team, or less often the contractor. Contractors and trades carry out much of the testing work under the CxA's oversight.

How commissioning works on a real job

Take a $9 million medical office building with a commissioning spec. The process usually looks like this:

  1. Owner's project requirements. The owner writes down what the building must do: hours, temperatures, redundancy, energy goals.
  2. Design review. The CxA checks the drawings against those requirements and writes comments, much like a constructability review focused on systems.
  3. Commissioning plan and checklists. The CxA issues prefunctional checklists that trades fill out as equipment is set and connected.
  4. Startup and functional testing. After the mechanical and controls subs start equipment, the CxA witnesses functional tests: valve strokes, economizer sequences, generator transfer, fire alarm interlocks.
  5. Issues log. Every failure goes on a log with an owner and due date until it is fixed and retested.
  6. Training and turnover. Facilities staff are trained, and the CxA delivers a final report and systems manual.

On that medical office, functional testing finds that two exam room VAV boxes are wired to the wrong thermostats. That is a 30-minute fix during commissioning and a months-long comfort complaint if nobody tests it.

Who pays and who does the work

The commissioning authority's fee is usually an owner cost. The trades' time to complete checklists, start equipment, attend tests, and fix issues is a contractor cost, and it has to be in the bid. Estimators who miss the commissioning section of the specs often underprice controls and mechanical scopes by days of labor.

Common commissioning problems

  • Controls programming finishing the week before turnover, leaving no time to test sequences.
  • Trades treating checklists as paperwork, which leads to failed functional tests and retesting charges.
  • Commissioning not on the construction schedule, so it collides with punch work.
  • Substantial completion requested before required tests are complete, which the owner can refuse under many contracts.
  • Seasonal testing (heating in summer, cooling in winter) left unplanned.

Related terms

See closeout, O&M manuals, quality assurance, and inspection. The guide on how to close out a construction project shows where commissioning fits in the last months of a job.

Frequently asked questions

What is the difference between startup and commissioning?

Startup is the installer energizing and checking equipment per the manufacturer. Commissioning verifies the whole system performs to the owner's requirements, including how systems work together.

Is commissioning required?

It depends on the code, the owner, and any certification goals. Some energy codes and owners such as federal agencies require it on certain projects; the specs will say so.

What is retro-commissioning?

Retro-commissioning applies the same process to an existing building that was never commissioned, usually to fix comfort or energy problems.

Who is the commissioning authority?

The person or firm that leads the commissioning process, writes the plan, witnesses tests, and reports to the owner.

Sources

  1. ASHRAE: Updated commissioning guideline (Guideline 0, the commissioning process)
Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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