What is the Purpose of Commissioning? (And why it matters)

You have been told commissioning is important. Every project brief says so. Every senior engineer nods along when it comes up. But if you are just starting out in your first commissioning role, that answer probably feels hollow.

You think, Important how? Important enough to justify the cost? Important to the owner, or to you personally?

This is what it actually means – and why the purpose of commissioning in a construction project matters.

The Core Purpose of Commissioning

The purpose of building commissioning is to verify that every system in a building – HVAC, electrical, plumbing, controls, and fire protection – is designed, installed, and operating exactly as the owner intended. Defined by ASHRAE Standard 202-2018 [which sets the commissioning process requirements] and delivered through the framework established in ASHRAE Guideline 0-2019 [which defines the process itself, from pre-design through occupancy and operations], it is a structured quality assurance process that protects the owner’s investment, reduces operational risk, and ensures the building performs safely and efficiently from day one.

That is the formal version. In plain language.

Commissioning is the mechanism that closes the gap between what was designed on paper and what actually operates in the building.

Commissioning (Cx) is distinct from testing. Testing vs commissioning is a question we cover separately, but the short version is; testing confirms that individual components function; commissioning verifies the integrated system performs against the Owner’s Project Requirements [OPR] – the documented statement of what the building is actually supposed to do. In practice, the OPR captures everything from temperature set points in each zone to air quality standards and emergency power sequencing – it is the agreed benchmark the building is measured against.

What Commissioning Actually Achieves

Commissioning is a quality assurance process, but that phrase can make it sound passive – like a final review at handover. It is not. It is an active, structured process that runs from pre-design through occupancy and operations, with the outcomes it delivers being measurable.

According to research from the Lawrence Berkeley National Laboratory [LBNL], new construction commissioning, when completed properly, can deliver a median energy saving of 13%. For existing buildings, that figure rises to 16% through retro-commissioning programmes. This information is taken from real project data across hundreds of buildings in USA.

The types of commissioning that deliver these outcomes range from new construction Cx through to ongoing and retro-commissioning for existing assets.

Beyond energy, the benefits of building commissioning extend into system reliability, indoor air quality, and long-term operational performance / maintenance.

Equipment that has been properly commissioned runs within its design parameters.

Controls that have been verified against the sequence of operations do not drift or do things that are not expected.

The building management team inherits documented proof of how every system was set up – which means they can maintain it.

The purpose of commissioning in this broader sense is to hand over a building that the operational team can understand, run, and over time, fine tune / improve.

Why is commissioning important as part of a construction project? Because construction produces buildings that are becoming significantly more complex. What commissioning provides is independent verification – a structured, impartial confirmation that systems are operating as required, not just installed and connected, and it is backed by rigorous documentation: pre-functional check records, functional performance test reports, deficiency logs, systems manuals, and a final commissioning report that the operational team can actually use and are trained upon.

Who This Matters To – Engineers, Owners, and Occupants

The benefits of commissioning land differently depending on what your role is on a project:

The Owner

The owner has a financial stake in every system performing as specified. A building that underperforms on energy, or fails early on critical equipment, costs the owner in operational spend – and those costs compound.

The Engineer

For a new engineers, the value of commissioning is different – and more immediate.

Understanding the purpose of commissioning makes you more effective on site. When you know why a pre-functional check exists, you complete it properly rather than as a box-ticking exercise. When you understand the commissioning process, sequence, the OPR, you can recognise when an installation is drifting away from it. When you understand the Basis of Design [BOD] – the designer’s record of every key decision, from system selection to performance targets – you understand what the design team intended and why + what is is based upon (the OPR).

Commissioning benefits for engineers go way beyond technical competence. It gives you traceable, documented evidence of your decisions on site. In a disputed handover, or a failure after handover, that documentation is the difference between a clean close-out and months arguments and finger pointing.

The Building Operator

The building operator is arguably the stakeholder most directly affected by commissioning quality – and the one least likely to have been in the room when the decision to scope or cut it was made (they should be there). They usually just inherit the outcome and what is given to them at handover.

What makes the operator’s position distinct is that they carry the consequences of a process they had no influence over. The engineer moves on. The contractor demobilises. The CxA closes out the report. The operator stays, and the quality of what commissioning delivered determines whether they are running a building or managing a building that runs them.

Retro commissioning exists partly because of this. When an existing building is performing below expectations – energy costs are higher than projected, occupant complaints are persistent, maintenance costs are climbing – the root cause is often a commissioning deficit from original handover. Operators are managing the consequences of decisions made years earlier, by people who had already moved on to the next project.

Getting commissioning right at handover is, for the building operator, the difference between a building they can run and a building they are constantly fighting with.

The Occupant

Occupants rarely know what commissioning is, to be honest they don’t need to know.

They experience it as outcomes: stable indoor temperatures, consistent ventilation, not being tired half way through the day, lighting that responds correctly and at the correct levels, fire systems that function in an emergency, toilets that flush properly.

In sectors where performance is critical – hospitals, pharmaceutical facilities, data centres – the occupant is entirely dependent on commissioning quality assurance to protect their operations and their clients / patients. A data centre that loses cooling due to a controls issue that commissioning would have caught, if used and done, can become a significant operational and financial problem.

The Cost of Skipping Commissioning

Skipping commissioning is a false economy. Yes, it removes a line item from the project budget and might shave a few weeks off the programme, but it does not remove what it manages; the risk — it defers it, usually into the operational phase, where the costs are exponentially higher and the people absorbing them had no say in the original decision.

The energy penalties are also immediate. Without commissioning, un-calibrated sensors, incorrect scheduling, and systems operating in conflict — a chiller and a boiler running simultaneously is more common than it should be. Equipment that was never set up within its design parameters run inefficiently, and it degrades. A fan running against a closed fire damper, or a pump installed with reversed rotation, will reach end-of-life years ahead of the buildings operating budget.

Operationally, a facility management team that inherits a building without a commissioning report inherits a building with no verified baselines, no optimised sequences of operation, and no proof of how any system was set up. They spend their first year as troubleshooters, manually overriding controls and chasing faults in the BAS that were never tested under load. The punch list that should have closed before handover bleeds into occupancy. Preventive maintenance becomes impossible because nobody established how the systems should run under normal conditions. They struggle to understand how the building and its systems work, because they were never trained.

Life safety becomes a problem, fire alarm systems, smoke exhaust, emergency generators, and stairwell pressurisation must integrate correctly during an emergency — and integrated system testing is how that integration is verified. Skipping it brings huge risk when you need to rely on those systems.

The $1 : $10 : $100 principle frames all of this clearly and what commissioning helps manage. A deficiency caught during pre-functional checks [$1 – contractor absorbs it] costs very little to resolve. The same deficiency found at functional performance testing [$10 – the owner starts bearing the cost in programme delay and coordination] costs considerably more. Found after handover, during the warranty or operational phase [$100 – the operator carries the full burden, often with walls closed and systems in use], the cost escalates again.

Commissioning does not eliminate deficiencies — construction produces them regardless. What commissioning does is catch them at the cheapest possible point in the timeline. The problems do not disappear when you skip commissioning; they transfer, and the people who inherit them are rarely the people who made the decision to cut the budget.

Is Commissioning Worth It? The Numbers

The short answer is yes.

Research from the Lawrence Berkeley National Laboratory [LBNL], which analysed commissioning outcomes across hundreds of buildings, found that new construction commissioning delivers a median energy saving of 13%. For existing buildings put through retro commissioning programmes, that figure rises to 16%.

The US General Services Administration [GSA] puts the operational picture alongside the energy data: commissioned buildings have 8–20% lower operating costs than equivalent non-commissioned buildings.

The Concord Group’s analysis, also frequently cited alongside GSA research, puts energy cost reduction at 3–13% for commissioned buildings.

When viewed altogether, the picture is very consistent, commissioning is not a quality assurance cost with zero return; it is an investment where performance can be measured with documented, repeatable outcomes across all building types.

On payback, the LBNL research found that the investment in commissioning, when correctly scoped and delivered, is typically recovered in under one year through energy and operational savings alone. That is before accounting for the cost savings, by running the process, of defects caught early, warranty disputes that never happen, and equipment that runs within its design parameters rather than fighting itself for years.

With the above in mind, the question is not really “whether commissioning is worth the cost”.

The question is “whether you can justify not doing it”.

What This Means If You’re an Engineer

If you are early in your career, the case for understanding what commissioning is, is straightforward, and engineers who understand why the process exists will be far more effective and prepared to deliver it.

Engineers who treat commissioning as a tick box exercise will miss the real value of it, and continue to struggle in the workplace and to get promoted.

If you are thinking about where commissioning fits in your career, our article how to become a commissioning engineer covers the path in detail.

Where to Go Next

This article is part of the CommissioningManager.com Pillar 1 cluster – a structured set of resources on what commissioning is, why it exists, and how it is delivered.

• Start with What Commissioning is: What Is Commissioning in Construction? A Complete Guide
• Understand the consequences: What Happens If a Building Is Not Commissioned?
• Understand accountability: Who Is Responsible for Commissioning on a Construction Project?
• See the full picture: Types of Commissioning in Construction – A Complete Breakdown