Wondering what the difference is between commissioning vs re-commissioning vs retro-commissioning? You’re not alone. These terms get tossed around all the time in the A&E world—often like they mean the same thing. But they don’t. And misunderstanding the differences can lead to scope confusion, missed deliverables, and buildings that don’t perform the way they should.

The truth is, each type of commissioning serves a different purpose depending on where a building is in its lifecycle. One applies to new construction. Another helps you fix drift over time. The third is for buildings that never got commissioned in the first place.

In this guide, we’ll break it all down clearly: what each process is, when to use it, and how it fits into your project workflow. We’ll also show how tools like Deltek can make managing these stages a whole lot easier—for you, your team, and the owner.

Let’s go!

What Is Building Commissioning?

Before we dive into the three different types, let’s ground ourselves in the basics.

Building commissioning is a systematic process that ensures a building and its systems perform as intended. It’s not just an inspection or a final test at the end of construction. It’s an integrated, multi-phase effort that starts early—ideally during the design phase—and carries through to occupancy and operations.

The commissioning process typically includes:

• Establishing performance requirements based on the owner’s needs
• Reviewing design documents for alignment with those needs
• Verifying that systems (HVAC, lighting, controls, electrical systems, plumbing, life safety, etc.) are installed and tested properly
• Documenting every step of the process so that building operators know how to maintain performance long after the ribbon is cut

Commissioning helps prevent systems from being installed incorrectly or operating inefficiently. It provides a third-party check that keeps design and construction teams accountable while making sure the end user gets what they paid for—a building that works.

So why break commissioning into three types? Because buildings change over time. Equipment ages, occupants shift, and system settings get overridden. The kind of commissioning that makes sense for a brand-new build is very different from what you’d do to get a 15-year-old commercial building back on track.

In the sections below, we’ll unpack commissioning vs re-commissioning vs retro-commissioning—each with its own purpose, timing, and value depending on where the building is in its lifecycle.

Wanting a deep dive into what commissioning is as a whole? Visit what is building commissioning for a more comprehensive look.

Commissioning

Commissioning is where it all begins. Think of it as laying the foundation for how a building should function—from day one.

It’s implemented during new construction or major renovations and ensures that all systems are designed, installed, and tested to meet the owner’s needs and the design intent. Done right, it bridges gaps between design, construction, and operations teams—before the building ever opens.

Core Components:

• Design Validation: Review drawings and specs against Owner Project Requirements (OPR). For help managing documentation and aligning with project goals, refer to our blog on building specifications.
• Construction Oversight: Inspect installations and conduct functional testing
• Integrated Systems Testing: Ensure system interoperability (e.g., HVAC + lighting + controls)
• Training + Turnover: Provide final documentation and train facilities staff

Why It Matters:

• Avoids first-day failures and change orders
• Boosts client confidence and energy performance
• Builds a strong operational foundation

That process hinges on clear documentation and accurate system verification—including detailed submittals that outline how materials and systems will be implemented. For a deeper look at how submittals fit into the project lifecycle, check out our comprehensive guide to construction submittals and how to manage them effectively.

But buildings don’t stay “new” forever. And that’s where re-commissioning comes in.

Re-Commissioning

Even well-commissioned buildings can drift over time. Schedules shift, occupancy changes, and system settings get overridden. Re-commissioning is your opportunity to realign performance with today’s conditions—without the cost of a full overhaul.

It’s a planned tune-up, not just a reactive fix.

Best Done When:

• It’s been 3–5 years since initial commissioning
• Layouts or major systems have changed
• There are recurring hot/cold complaints or energy concerns

What It Involves:

• Trend Analysis: Use BMS data to identify inefficiencies
• Equipment Testing: Verify current function vs. current needs
• Control Updates: Remove overrides, fine-tune schedules
• Ops Alignment: Adjust for how the building is actually used

Why Re-Cx Works:

• Restores performance with minimal capital cost
• Improves comfort and occupant satisfaction
• Extends the lifespan of systems

But what if the building never had a commissioning process in the first place? That’s where retro-commissioning steps in.

Retro-Commissioning

Older buildings often operate like mysteries. Documentation is spotty. Systems were installed piecemeal. No one remembers the original design intent. Retro-commissioning (RCx) is a powerful diagnostic process designed to uncover hidden issues in these legacy buildings—and optimize them for modern performance.

Unlike re-commissioning, RCx starts from scratch. No assumptions. No shortcuts.

RCx Is Ideal For:

• Buildings built before 2000 or never commissioned
• Sites with outdated controls or persistent performance problems
• Facilities lacking baseline documentation

What It Includes:

• Energy Benchmarking: Establish baseline usage and performance
• System Assessments: Evaluate interaction between HVAC, lighting, and controls
• Corrective Actions: Implement low-cost fixes
• Stakeholder Interviews: Leverage institutional knowledge from staff

Payoff Potential:

• Significant energy and O&M savings
• Roadmap for future upgrades
• Increased occupant trust and operational clarity

RCx takes more time and digging—but the upside is often huge, especially for owners facing rising energy costs and system unreliability.

Quick Comparison: Understanding the Differences

Here’s a quick comparison showing the differences between the three concepts:

Feature	Commissioning	Re-Commissioning	Retro-Commissioning
Timing	New builds or renovations	Post-occupancy tune-up	Existing buildings (never Cx’d)
Goal	Confirm design performance	Re-align with usage changes	Fix undocumented or degraded systems
Documentation	Provided during project	May need updates	Often lacking or outdated
Team Involvement	Original project team	Some overlap	Often new personnel
ROI	High, front-loaded	Moderate to high	High, with more discovery

You can use this table when explaining to co-workers the differences or when guiding clients through the options—it’s especially useful during proposal conversations or budget justifications.

For a detailed overview of implementation, tools, and timelines, check out the commissioning process step-by-step guide.

Common Missteps to Avoid

Let’s be honest—even the most seasoned A&E professionals can stumble when it comes to commissioning workflows. With so many teams, stakeholders, and moving parts, it’s easy to lose track of where responsibility starts and stops.

The mistakes listed below aren’t theoretical. They come from the field, from real-world projects where commissioning got deprioritized, mismanaged, or tacked on as an afterthought. Here’s how to avoid falling into those traps:

Commissioning

• Waiting too long to engage a commissioning agent: If you’re looping them in at the tail end of construction, you’re not commissioning—you’re troubleshooting. Real commissioning starts early, during design review, so the Cx agent can identify potential coordination gaps before they turn into field problems.
• Treating commissioning like a line item, not a process: When it’s seen as a contractual requirement to check off instead of a system-wide QA method, things slip through the cracks. The outcome? Systems that technically “work” but don’t perform as expected.
• Leaving out the facilities team: If the people who will actually operate the building aren’t part of commissioning conversations, you risk installing systems that are too complex, incompatible with staff knowledge, or impossible to maintain.

Re-Commissioning

• Chasing complaints instead of using data: Don’t wait for a flood of hot/cold calls to realize your systems are off. Building automation systems are packed with trend data. Use it.
• Making changes without documentation: Re-Cx often involves overrides, adjustments, and logic changes. If those aren’t captured, the next team is left guessing. Worse, the same issues may reappear later.
• Waiting until things go wrong: Re-commissioning isn’t just a fix—it should be part of a building’s maintenance rhythm. Set a schedule (every 3–5 years) and stick to it, even if no one’s complaining… yet.

Retro-Commissioning

• Underestimating how messy it can get: Older buildings are like detective cases. You might be missing drawings, facing undocumented retrofits, or dealing with systems installed by three different contractors over two decades. Build in time and budget for the unexpected.
• Jumping in without clear goals: “Let’s fix what’s broken” isn’t enough. RCx should start with specific performance goals, whether it’s energy use targets, comfort complaints, or equipment reliability.
• Missing the people piece: Operators often know what’s wrong—they’re just not asked. Use the process to train, retrain, and bring them into the loop. That makes your fixes stick longer.

Every commissioning process—whether initial, repeat, or retrospective—works best when it’s intentional, integrated, and people-centered. Make space for it upfront, and your project delivery gets smoother, your owners get better buildings, and your reputation stays solid.

How Deltek Supports Commissioning from Start to Finish

Managing commissioning, whether it’s for a new build, an upgrade, or a retrofit, requires real coordination across design, engineering, and facilities teams. That’s where Deltek stands out. While Deltek is widely known for project and financial management, it also plays a vital role in supporting building commissioning from early planning through operations.

Specification Development with Specpoint

One of the most critical pieces of successful commissioning is getting the specifications right. Deltek’s Specpoint platform, built on AIA MasterSpec, helps A&E teams develop, manage, and maintain building specifications that clearly outline performance requirements, system standards, and compliance expectations.

• Aligns project specs with Owner Project Requirements (OPR)
• Ensures the design matches commissioning expectations from the start
• Makes coordination between disciplines easier and more transparent

Project and Cost Tracking

Commissioning efforts live and die by their ability to stay aligned with project budgets and schedules. Deltek’s project management tools help keep everything on track:

• Assign and track commissioning activities, milestones, and task owners
• Link commissioning issues with RFIs, change orders, and schedules
• Monitor commissioning-related costs across design and construction phases

Lifecycle Coordination and Documentation

Whether you’re doing initial Cx, re-Cx, or retro-Cx, the success of the process often comes down to communication and recordkeeping. Deltek helps bridge gaps between teams:

• Centralizes documents, test results, and issue logs
• Tracks updates and changes across different commissioning phases
• Ensures historical documentation is maintained and accessible for facilities teams

The Real-World Payoff

When A&E firms use Deltek to support commissioning efforts, they gain:

• Better collaboration between design, engineering, and O&M stakeholders
• Stronger cost control on commissioning-related scopes
• More consistent project delivery with fewer late-stage surprises

Commissioning doesn’t happen in a vacuum—it touches nearly every part of the project. With Deltek, A&E teams can manage specs, timelines, budgets, and documentation all in one place.

If you’re evaluating commissioning tools, building commissioning software is a must-read.

Final Thoughts: Commissioning vs Re-Commissioning vs Retro-Commissioning

Commissioning, in all its forms, is about building resilience into your building projects. It’s how A&E firms ensure that design excellence translates into operational success. And by understanding the unique purpose of commissioning, re-commissioning, and retro-commissioning, you can:

• Proactively address performance issues before they escalate
• Plan smarter handoffs between design, build, and operate teams
• Position your firm as a long-term partner in building success

Here’s the bottom line: whether you’re guiding a new build, troubleshooting aging systems, or looking to boost energy performance, commissioning is your most reliable lever. Treat it as the strategic investment it is—and make it a core part of your project delivery.

Key Takeaways

• Commissioning, Re-Commissioning, and Retro-Commissioning each serve different phases of a building’s life—but all aim to ensure systems perform as they should.
• The earlier you bring commissioning into the project lifecycle, the more value you get—especially when it’s aligned with design intent and operational goals.
• Re-Commissioning should be built into your facility maintenance plan, not treated as a last resort.
• Retro-Commissioning is one of the most impactful ways to improve performance in older buildings—but it requires time, investigation, and buy-in from facilities teams.
• Technology platforms like Deltek Vantagepoint can support commissioning workflows by connecting specs, schedules, documentation, and handoffs across teams.

Frequently Asked Questions