The American Society of Heating, Refrigerating and Air-Conditioning Engineers has published an energy standard for data centers.

Known as standard 90.4, it establishes the minimum energy-efficiency requirements of data centers for design and construction, including the creation of a plan for operation and maintenance, and for utilization of on-site or off-site renewable energy sources.

“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 90.4 committee. “It is important to keep in mind that data centers are mission-critical facilities, where risk management is the primary concern.”

As a performance-based standard, 90.4 offers design components for mechanical load, electrical loss and sample calculations. Other requirements in the standard include a sample compliance checklist and diagrams to illustrate compliance.

“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 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 not 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.”

To purchase a copy of ASHRAE’s data center standard, visit or call (800) 527-4723.