Commissioning scope and phases

Where the value actually sits in the programme

A commissioning assignment is often bought late, when a certification body flags a missing prerequisite. By then a third of it is already behind the project. This page sets out what happens at each phase, what it produces, and why the sequence cannot be reordered.

Discuss a project Certification requirements

Phase 1

Brief: writing down what is expected.

Everything that follows is measured against a document that most projects never write: a clear statement of the performance expected from the building, the conditions under which it will be used, the service levels required and the assumptions accepted. North American practice calls this the owner's project requirements; French schemes have adopted the same idea under their own name.

Without it, verification has no reference. It degrades into a check that equipment starts, which is what most handovers actually deliver. With it, every later stage has something to compare against — and the client has a document that survives changes of project manager, of design team and of operator.

Its counterpart on the design side is the basis of design, which explains how the requirements are to be met. The pair is what makes a design review possible at all.

Phase 2

Design: the phase nobody buys, and the one that pays.

Two deliverables matter here, and both are cheap to produce and impossible to recover later.

  • The critical design review. Reading drawings and specifications against the stated requirements, identifying what will not be verifiable as designed, and flagging what the operator will not be able to run. Issues raised at this point cost a revised drawing; the same issues raised during construction cost a variation.
  • The testing clauses in the works packages. Without them, the commissioning provider has no contractual grip on the contractors: no attendance rights at tests, no obligation to supply the functional description or the loaded parameters, no defined acceptance criteria. This is the single most consequential document of the whole assignment, and it is written months before anyone thinks about commissioning.

Certification schemes recognise this. LEED version 5 requires the commissioning professional to be appointed during pre-design or very early design for its enhanced credit, precisely because the credit's value lies in what happens at this stage.

Phase 3

Construction: one register, not five email threads.

During construction the assignment reviews contractor submittals against the design intent, attends verifications, and — crucially — maintains a single issues register. Not a list per trade, not a thread per meeting: one register, with each item carrying an owner, a date and a resolution.

This sounds administrative and it is the difference between an assignment that produces evidence and one that produces opinions. On a phased or occupied project, where the installation changes state at each handover, the register is the only thing that retains what was verified, when, and in which configuration.

It also carries the point that matters at the end: the distinction between what the contractor still owes and what the client has accepted. That distinction is what allows the one-year statutory completion guarantee to be used rather than discovered too late.

Phase 4

Handover: comparing the description with the machine.

Functional testing at handover verifies the contractor's own set-up work — it does not replace it. The set-up belongs to the contractor and to the contractor alone; commissioning checks that it was properly done and keeps the record.

The most productive check at this stage is also the least performed: comparing the functional description with the parameters actually loaded into the controllers. The document and the machine diverge far more often than anyone expects, and nobody verifies this after start-up. Commissioning overrides left in place, schedules on default values, setpoints changed during a site visit and never recorded — none of it appears in a snagging list, all of it costs money for the life of the building.

The other decisive deliverable is the transfer to the operator, with training. An operator who does not understand a control strategy neutralises it. That is not obstruction; it is the only way to answer a complaint when you have no visibility of what the system is doing.

Phase 5

First year: using the guarantee while it runs.

The French statutory completion guarantee runs for one year from handover. It is the only period during which a contractor puts right what does not work, at their own cost. After that, a settings correction is procured and paid for.

Control faults, however, only reveal themselves under seasonal load. An unbalanced heating circuit is invisible in September and obvious in January; excessive night ventilation shows up in February; a poorly sequenced cooling strategy waits for July. The practical question is therefore how many seasons the guarantee actually covers — and the answer depends on the handover date. A building handed over in June sees a full winter inside the guarantee. The same building handed over in February does not.

This is the strongest argument for engaging the assignment before handover rather than after. Beyond the first year, the same work continues under the name ongoing commissioning, or is applied to an older building as retro-commissioning.

FAQ

Practical questions about scope.

It can, and it frequently does, but it delivers a fraction of the service for the same fee. The brief and the design review are behind the project, and — more importantly — the works packages have already been let without testing clauses, which removes the contractual grip on contractors. What remains is worth doing, but it should be bought knowing what has been forfeited.
The testing clauses inserted into the works packages, written long before anyone thinks about commissioning. Without them there is no attendance right at tests, no obligation to supply the functional description or the loaded parameters, and no defined acceptance criteria. Everything the assignment does later depends on that document.
Because they diverge far more often than anyone expects, and nobody checks after start-up. Commissioning overrides left in place, schedules on default values, setpoints changed during a site visit and never recorded: none of it appears on a snagging list, and all of it costs money for the life of the building. The check takes hours and is almost never specified.
It depends entirely on the handover date, and this is worth arbitrating early. The French completion guarantee runs one year from handover, while control faults only reveal themselves under seasonal load. A building handed over in June passes a full winter inside the guarantee; handed over in February, its first genuinely tested winter falls after expiry. At equal build quality, the handover date decides who pays for the corrections.

Go further

The rest of the commissioning material.

Scoping an assignment?

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