Data Center HVAC and the Race to Improve PUE

data center HVAC

Guest Blog By Scott Wilson,


Every industry has different ventilation and cooling needs that require some level of customization when designing and building systems to meet those demands. You could even say there are as many specialties in the HVAC trade as there are unique ways to tailor systems to different industrial applications. But few have emerged as quickly or have as big a role in the future of the trade as the specialized systems used to keep data centers cool.

Data centers are the engines that run the internet and are what make distributed computing possible, offering efficient performance at a low price. The trend of software being offered as a service (like Microsoft’s Office 365 product) and with the likes of Facebook and Google keeping all their horsepower in remote facilities, thousands and thousands of servers housed in data centers around the world are relied upon to run continuously day and night.

The internet never sleeps and data centers must never go down. Billions of dollars of commerce and information flow through those wires, so data center HVAC work is also mission critical. This has meant incorporating redundancies to keep temperature, humidity, and particulate count within acceptable parameters even if some units go down or if electricity fails.

By all accounts, the reliance on remote data centers will only increase for the foreseeable future. In fact, according to Data Center Dynamics, construction of new data centers will increase at a rate of about nine percent per year through 2019.

Data centers are all about power, and as the laws of thermodynamics dictate, that power turns into heat at some point. Without massive cooling arrangements, all those vital servers would eventually turn into molten metal.


Data Center HVAC Has Come a Long Way


Power Usage Effectiveness (PUE) is the metric used to measure the energy efficiency of data centers. To find the PUE, you simply take the total energy required to run a data center (including everything from lighting to HVAC) and divide it by the energy used just to run the servers. In 2007, the average PUE for all U.S. data centers was 2, meaning that 2 watts of overhead energy was used for every 1 watt used for computing power.


The initial approach to data center cooling was just to drop in big coolers and fans as a way to muscle through the heat. But since even a small reduction in that PUE number can mean millions of dollars in savings on energy consumption, there was a major incentive to develop more efficient and specialized systems.


Designs evolved to make use of hot and cool aisles, with servers venting into a hot aisle and large overhead plenums sucking the hot air into chillers to bring the temperature down. Cold air would then be pushed out again beneath raised floors and vented into the cool aisles, where the front edge of the servers would pull it in again.


Although this technique provided real advantages over brute-force, whole-room cooling, many HVAC contractors are taking it further still. Now, some centers are expressly located in cold climates to make maximum use of external air temperatures and reduce the reliance on chillers. Others use passive circulation techniques to reduce the need for powerful circulating fans.


Advances in HVAC design strategies and technology drove the average PUE down to about 1.7 by 2014. But some data center operators have gone even further, with Google hitting an average PUE of 1.12 across all its data centers as of early 2017.


A low PUE is a competitive advantage and HVAC contractors that can put in systems to drop that ratio have a serious edge over the competition. The latest methods for achieving new lows in that PUE number may not even be publicized yet.


As a relatively new practice area, data center HVAC work is also evolving at a much more rapid pace than other areas of the trade. According to Google’s VP of Data Center Operations, in almost seven years, the internet giant changed their data center cooling strategy five different times.


The tolerances and requirements to hit low PUE ratios while maintaining a high degree of reliability aren’t something you just learn on the job. Understanding the science behind air circulation and the refrigeration cycle are concepts you need on day one, making formal education and training more important for preparing to enter the trade than ever before.


Scott is an IT consultant based in the North West and the lead contributor for As a dedicated resource for people exploring HVAC education and training options, the staff at works hard to keep up with the latest developments in the industry as a way to keep students and trades-people ahead of the curve.

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