Summary
Gordon Johnson discusses how data center cooling has evolved over the past three decades, the impact of AI-driven workloads on facility design, the growing role of hybrid air and liquid cooling systems, and why airflow management and CFD modeling remain critical for efficiency and long-term infrastructure planning.
An Interview with Gordon Johnson, Senior CFD Manager at Subzero Engineering
As artificial intelligence, high-performance computing, and increasingly dense IT environments continue to reshape the data center industry, operators are facing new challenges in cooling, airflow management, efficiency, and long-term sustainability. Technologies that were once considered emerging are now becoming essential components of modern infrastructure strategies.
To help make sense of these changes, we sat down with Gordon Johnson, Senior CFD Manager at Subzero Engineering. With more than three decades of experience across data centers and cleanroom environments, Gordon has helped organizations around the world optimize cooling performance, improve energy efficiency, and prepare their facilities for the next generation of computing demands.
In his role at Subzero Engineering, Gordon leads Computational Fluid Dynamics (CFD) modeling projects across North America, EMEA, and APAC while providing training and guidance on containment, cooling strategies, airflow management, and data center best practices. He is also a frequent industry speaker, sharing insights on the technologies and trends shaping the future of mission-critical facilities.
In this interview, Gordon discusses the evolution of data center cooling, the growing importance of hybrid air and liquid cooling strategies, common misconceptions surrounding airflow management, and why cooling has become one of the most strategic infrastructure decisions operators face today.
Whether you’re designing a new facility, planning for AI workloads, or looking to improve the efficiency of an existing data center, Gordon’s insights offer valuable perspective on where the industry is headed—and how organizations can prepare for what comes next.
What is your role today at Subzero Engineering, and how did your journey into the data centre industry begin?
As Senior CFD Manager, I manage all of our CFD modeling projects across the US, EMEA, and APAC regions, as well as deliver our internal and external training on data center design, containment, cooling strategies, and CFD best practices. My role focuses on improving efficiency and operational performance in legacy and next-generation data centres. In addition, I work closely with our global sales and engineering teams to ensure customers receive accurate, highperformance containment solutions that are tailored to their facilities.
Also, I regularly speak at industry events on data center cooling, containment, and emerging trends shaping the future of our industry.
You’ve spent more than 30 years working across data centres and cleanroom environments. What changes have had the biggest impact on how facilities are designed and operated today?
When I initially entered the industry, efficiency and energy savings were largely seen as an afterthought in data center management and operation. As recently as 10–15 years ago, the prevailing mindset for data center cooling was simply ‘the colder, the better.’ Beyond driving massive energy bills, this approach wasted natural resources and expanded our carbon footprint.
Fortunately, the industry has since shifted its perspective, with many facilities now operating supply temperatures near the upper end of ASHRAE’s recommended serverinlet guidelines, ensuring efficiency and a closer connection to the industry’s ambition for a more sustainable future.
Looking back across your career, what have been some of the most important lessons you’ve learned about designing resilient infrastructure?
Looking back on my career in the data center industry, one of the most important lessons I’ve learned is that simplicity is often what drives reliability and performance.
Data centers constantly evolve, and the demand for high-performance computing densities are growing, so those in the industry must design their facilities to adapt to changes without requiring complete redesigns. Containment is a perfect example of simplicity at play, which is why I’m so passionate about the topic. Rather than consuming energy, effective containment reduces energy use and makes every other efficiency initiative more impactful and costeffective. It reinforces a principle I’ve come to fully embrace – the best energy saved is the energy you never consume in the first place.
As AI workloads push rack densities higher, how is the industry’s approach to cooling and airflow evolving?
As recently as 2020, a 20 kW rack qualified as HPC (High Performance Computing). Today, AI and machine learning workloads routinely drive rack densities to 100 kW and beyond, with demand continuing to climb. This rapid escalation is a key reason hybrid cooling, combining air and liquid systems to handle both low and highdensity racks, has become the industry’s evolving standard for efficient cooling regardless of the workloads deployed.
The industry is recognising that future-ready data centres must combine liquid cooling with highly disciplined airflow management systems to support the evolving needs of the competitive market.
There’s growing conversation around liquid cooling, immersion, and direct-to-chip technologies. How do you see these approaches fitting together within future data centre environments?
Future data centre environments must consider using a hybridised approach into their cooling technologies, so I expect to see this in next generation environments. It will be common to see directtochip, immersion, and air-cooling solutions operating side by side within the same facility depending on the density requirements, operational priorities, and sustainability goals. What is also important to note is seeing a more deliberate separation between highdensity and lowdensity ITE, which is ultimately how operators will maximize efficiency.
What do you think operators still misunderstand about airflow management and thermal efficiency in modern facilities?
Some people don’t realize that the most common form of liquid cooling—directtochip (DTC) — still relies heavily on air cooling strategies. DTC cold plates remove heat only from the highestload components such as CPUs and GPUs. The remaining server and rack heat must still be removed by traditional air systems. Since roughly 75% of the heat is captured by the liquid loop, a 100 kW rack still requires enough airflow to remove the remaining ~25 kW. To do this effectively, proper coldaisle or hotaisle containment is also essential.
At what point does cooling become a strategic infrastructure issue rather than simply an operational one?
Cooling has now become a strategic infrastructure consideration, directly impacting scalability, operational cost, sustainability ambitions, and the competitive market advantage. With AI and HPC, cooling is now shaping the entire data center infrastructure, including power, layout, sustainability, and total cost of ownership, moving away from being seen as an operational issue the moment it limits what can be deployed. We’ve hit the point where cooling is no longer something we operation, but rather it’s something we must strategically design for the future industry.
How can operators balance rising compute demand with growing pressure around sustainability, energy efficiency, and resource use?
The key to balancing rising computing demand with growing pressures is to first, pause and take a breath – not every rack moving forward will be running AI or ML workloads. At the same time, we must design and engineer nextgeneration data centers to be sustainable, energyefficient, and relevant for the next 10 to 15 years. Constant threeyear ripandreplace cycles of both hardware and cooling aren’t viable. We need a balanced approach that prioritizes smart, longterm TCO decisions.
What role do modelling and simulation technologies like CFD now play in improving operational efficiency and long-term planning?
CFD has evolved from being a design validation tool into a strategic operational tool. It is still very much needed, even in data centers that deploy direct to chip liquid cooling. In many cases, this has become more important, not less.
For example, CFD is needed to validate the airflow is still delivered correctly and that no hotspots form around non liquidcooled components since CFD is the only tool that can accurately model how that remaining heat behaves in the white space. CFD is also the only way to simulate transient and failure scenarios safely.
As infrastructure becomes more complex, CFD modelling becomes more important as operators can no longer rely on previously used design approaches alone.
Looking ahead five years, what’s one bold prediction you would make about the future of cooling and thermal management in the data centre industry?
Data center cooling and thermal management will continue to evolve over the next five years and well beyond. We expect ongoing adoption of hybrid cooling, through integrating air and liquid systems, to increase capacity, efficiency, and sustainability. Moving forward, data center design and cooling infrastructure will no longer follow a one-size-fits-all model, so all of us in the industry need to evolve and adapt to this way of thinking.