ASHRAE says its new energy standard for data centers is more flexible to meet the needs of that fast-changing industry.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers’ standard 90.4 sets minimum energy-efficiency requirements for data centers, including design, HVAC construction, operation and maintenance. It also encompasses the use of renewable energy sources, whether located on- or off-site.

“We worked very hard to craft this standard in a manner that does not stifle innovation in the data center industry while simultaneously offering criteria to help ensure energy savings,” said Ron Jarnagin, chairman of the committee that wrote the standard. “It is important to keep in mind that data centers are mission critical facilities where risk management is the primary concern.”

He said that high plug loads and quickly changing information technology make data centers very different from standard commercial structures. The standard takes that into account.

“The committee initially pursued a green grid power use effectiveness-like (PUE) process for setting the criteria in the standard but the green grid’s PUE metric is actually based on measured energy use data rather than design criteria calculations,” Jarnagin said. “We realized that the design calculations contained in standard 90.4 would not likely match up with the actual energy use data so this approach was amended. We feel that we’ve recommended the requirements for 90.4 based on a justifiable 80/20 rule where only the lower performing systems will be affected.”

More information on the standard is at