Commissioning and the Swiss Cheese Model

Because ‘It Should Work’ Isn’t a Strategy

In construction and building operations, errors, omissions, and failures can have costly and even dangerous consequences. The Swiss Cheese Model, commonly used in risk management, is a powerful way to understand how building commissioning helps prevent these issues by creating multiple layers of defense.

When Holes Align: How Skipping Commissioning Turns New Buildings into Swiss Cheese Nightmares

Picture this: a gleaming new office building opens its doors. The ribbon’s cut, the HVAC hums, and everyone’s thrilled—until the first power outage results in very high door opening forces because supply fan interlocks were not tested. Or the utility bill is 5X more than expected because equipment is running before and after planned occupancy. What went wrong? Enter the Swiss cheese model, a good way to understand why skipping commissioning in new construction can turn a dream project into a cascade of failures. Let’s slice into it.

The Swiss cheese model is a framework used to understand how accidents or failures happen, especially in complex systems like healthcare, aviation, or engineering. It’s not about literal cheese but borrows the idea of Swiss cheese—full of holes—to explain how risks slip through the cracks when multiple layers of defense fail.

Imagine several slices of Swiss cheese stacked together, each representing a layer of defense (such as design reviews, inspections, and testing). Each slice has holes—gaps where errors or failures can slip through. However, when multiple layers are in place, the holes rarely align perfectly, preventing a full pathway for failure.

The Core Idea

Each slice of Swiss cheese represents a layer of protection in a system. The holes are weaknesses or errors in each layer, like human mistakes, faulty tools, or unclear rules. Normally, these layers overlap so that a hole in one is covered by solid “cheese” in the next, stopping problems from getting through. But when the holes align across all layers, a hazard can pass straight through, leading to a failure—like a plane crash, a medical error, or a data breach.

In building construction, failures don’t usually result from a single mistake but rather a series of missteps across different phases, from design to operation. This is where building commissioning acts as a critical safeguard, adding extra layers of oversight to catch potential issues before they lead to costly rework or operational failures.

Who Came Up With It?

The model was developed by James Reason, a British psychologist, in the 1990s. He used it to study human error and system safety, arguing that accidents aren’t usually just one person’s fault but the result of multiple breakdowns piling up. Reason split these failures into two types:

• Active Failures: Immediate mistakes by people at the front line (e.g., a pilot missing a warning light).

• Latent Failures: Hidden flaws baked into the system over time (e.g., poor training or budget cuts).

Why It’s Useful

The Swiss cheese model shifts blame from individuals to systems. It’s a call to plug holes proactively—fixing training, clarifying rules, or upgrading tech—rather than waiting for a disaster to point fingers. In industries like aviation, it’s helped cut accident rates by focusing on redundancy and catching latent issues early.

Commissioning as the “Cheese Layers” in Construction

Building commissioning (Cx) systematically ensures that all systems function as intended through planning, verification, and testing. Here’s how commissioning aligns with the Swiss Cheese Model to prevent errors:

1. Design Review – Catching Errors Early

• The Risk: Design flaws and omissions can lead to constructability issues, system inefficiencies, or operational problems.

• Commissioning Defense: A commissioning authority (CxA) reviews design documents to identify inconsistencies, missing details, and conflicts before construction begins.

2. Submittal Review – Ensuring Proper Equipment and System Application

• The Risk: Misinterpretation of designs, poor documentation, or lack of specificity.

• Commissioning Defense: A commissioning authority (CxA) reviews submittals to identify inconsistencies, missing details, and conflicts before construction begins.

3. Construction Oversight – Ensuring Proper Installation

• The Risk: Misinterpretation of designs, poor workmanship, or lack of coordination between trades can lead to system failures.

• Commissioning Defense: Regular site inspections verify that equipment is installed per design intent, manufacturer recommendations, and industry standards.

4. Functional Testing – Identifying Hidden Defects

• The Risk: Even properly installed systems may not function as expected due to integration issues, software glitches, or calibration errors.

• Commissioning Defense: Functional performance testing (FPT) systematically verifies that systems perform under real-world conditions, uncovering hidden problems before occupancy.

5. Training & Documentation – Preventing Operational Mistakes

• The Risk: Facilities teams may not fully understand how to operate or maintain systems efficiently, leading to premature failures.

• Commissioning Defense: Comprehensive training and clear documentation ensure that building operators know how to manage systems properly, reducing the risk of human error.

6. Post-Occupancy Optimization – Continuous Performance Assurance

• The Risk: Over time, system performance can drift due to changes in occupancy, control settings, or neglected maintenance.

• Commissioning Defense: Ongoing monitoring and analytics (through retro-commissioning or continuous commissioning) help identify performance degradation and inefficiencies before they become critical failures.

Real-World Impact: Preventing Costly Mistakes

Consider a newly constructed commercial office building. Without commissioning, HVAC systems might be installed incorrectly, leading to poor temperature control, excessive energy use, and tenant complaints. Electrical systems could have hidden defects, causing unexpected outages. By applying commissioning, these issues are caught and corrected early, avoiding expensive rework, lawsuits, or long-term inefficiencies.

Why Commissioning Plugs the Holes

Commissioning isn’t glamorous—it’s technicians verifying installations, calibrations, sequences, and scribbling notes. But it’s the glue that holds those cheese slices together. Here’s how:

• Catches Design Flaws: Tests reveal if the HVAC can cool a packed office, not just a sketch.

• Fixes Install Goofs: Spots that loose wire or clogged drain before move-in day.

• Forces Accountability: Contractors can’t dodge sloppy work when systems are proven live.

• Prevents Day-One Chaos: Owners get a building that works, not a fixer-upper disguised as new.

Think of it like baking a cake. You don’t pull it out half-cooked and call it done—commissioning is the toothpick test to ensure it’s ready.

The Cost of Skipping It

“Sure,” you say, “but commissioning costs time and money!” True—it might add 1–3% to a project budget. But fixing failures later? That’s 10–20% or more, plus lawsuits, lost tenants, and a trashed reputation. A flooded data center or a silent fire alarm isn’t cheap. Commissioning’s an investment—skip it, and you’re gambling with bigger losses.

No Whey Around It - Commissioning Matters

Whether your business has 20 or 2,000 employees moving into a new space, commissioning matters. Imagine your team’s productivity tanking because the air handler is down, lighting controls are not working, door pressures are too high or hot water is too cold—issues commissioning could’ve caught. The Swiss cheese model shows us: every layer counts. Without that early testing, you’re one hole away from a domino effect of breakdowns.

So next time you’re in a shiny new building, ask: Did they commission this building? Because when those Swiss cheese holes line up, it’s not just a leaky faucet—it’s a full-on facility flop.