How is commissioning different from testing?

Testing confirms a piece of equipment functions — the fan runs, the circuit is live, the pump turns. Commissioning confirms the system delivers what the design intended, in the building, with everything connected. A fan can pass a test and still deliver the wrong airflow to the wrong rooms; only commissioning finds that.

And how is it different from snagging?

Snagging is visual and about finish quality — a scratched door, a misaligned tile. Commissioning is about performance and is largely invisible. A space can be snag-free and badly commissioned, which is exactly the building that looks immaculate on handover day and generates complaints for a year.

What does air balancing actually mean?

Adjusting dampers and settings so each space receives the airflow the design allocated to it, and the total matches the system's design. Without it, air follows the path of least resistance — rooms near the plant are over-supplied and distant rooms are starved, regardless of what the equipment schedule says. It is the single most common gap in an office handover.

Why does commissioning get squeezed?

Because it sits at the end of the programme, after every preceding delay has accumulated, and because it is invisible to anyone walking the floor. When a date is fixed and the works are late, commissioning is the easiest thing to compress — and the consequences do not appear until the building is occupied, by which time the cause is arguable.

What evidence should a client receive?

Recorded results, not assurances: airflow readings against design figures room by room, water flow rates, electrical test results, control and interface test records, fire system test certificates, and the commissioning method statement they were produced against. If the only evidence is a signed statement that commissioning was done, it effectively was not.

What about system interfaces?

This is where commissioning most often falls short. Individual systems get commissioned by their own contractors, but the interfaces between them — fire alarm shutting down air handling, smoke dampers closing, access control releasing on alarm, generator picking up the essential load — belong to nobody in particular. Those cause-and-effect tests must be scheduled and witnessed explicitly, or they are skipped.

Commissioning Explained | Hagerstone International

Why it matters on a project

Most post-occupancy complaints about a new office are not construction defects. They are commissioning gaps.

"Half the floor is cold and the other half is warm." "The meeting room is stuffy." "The lights do not respond to the sensors." In almost every case the equipment is correct, installed and working — it has simply never been set up to deliver what the design intended.

That is why commissioning deserves attention from the client side, even though it is the least visible part of a fit-out.

Three different activities that get confused

Activity	Question it answers	Visible?
Testing	Does this equipment work?	Partly
Commissioning	Does the system deliver the design intent?	No
Snagging	Does the finish look right?	Entirely

A project can pass the first and third and fail the second completely, and nothing on a walk-through would reveal it.

The parts most often missed

Air balancing. Rooms get the airflow the design allocated, measured and recorded. Without it, distribution is decided by pipe and duct resistance rather than by design.
Control strategy. Not whether controls function, but whether they behave as intended — setpoints, schedules, sensor response, sequencing.
Interfaces between systems. Fire alarm to air handling, dampers, access control, generator changeover. These belong to no single contractor and are skipped unless scheduled and witnessed.
Fresh air quantities. Frequently assumed rather than measured, with ventilation rates commonly referenced to ASHRAE 62.1.
Electrical testing records, in line with the installation practice adopted, commonly with reference to IS 732.

Testing and commissioning provisions for building services sit within NBC 2016, Part 8, and the specific regime for a project must be set by the MEP consultant.

What to insist on

Ask for numbers, not statements. A commissioning record should show measured values against design values, room by room and system by system, with the date and who took them.

Ask for the cause-and-effect test record for interfaces, witnessed.

And put commissioning in the programme as a duration with a start date, not as an activity that happens in whatever time remains.

Common mistakes

Compressing it when the programme slips. The consequences surface after occupation, when they are hardest to attribute.
Accepting a signature instead of readings. No data means no commissioning.
Assuming interfaces were tested. They belong to nobody by default.
Occupying before commissioning completes. Balancing a floor full of people and furniture is far harder than balancing an empty one.
Treating snag-free as proof. Appearance and performance are unrelated here.

Standards referenced

Testing and commissioning provisions for building services in NBC 2016, Part 8; ventilation rates commonly referenced to ASHRAE 62.1; electrical installation practice in IS 732. The commissioning scope, method and acceptance criteria for a specific project must be established by the project's MEP consultant.

Commissioning: Proving the Building Actually Works

Why it matters on a project

Three different activities that get confused

The parts most often missed

What to insist on

Common mistakes

Standards referenced

Standards referenced

Frequently asked

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