“The proposed standard is intended to work in concert with ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings,” said Ron Jarnagin, chair of the Standard 90.4 committee. “There is no intent to duplicate what is contained in Standard 90.1, but rather we are proposing criteria to support the specialized nature of the larger data centers. When adopted, design and construction of data centers will require the use of both Standards 90.1 and 90.4 for compliance with building codes.”

David Quirk, chair of ASHRAE’s Technical Committee 9.9, Mission Critical Facilities, Technology Spaces and Electronic Equipment, noted that the intent of Standard 90.4P is to create a performance-based approach that would be more flexible and accommodating of change, which can occur rapidly in data center design, construction, and operation.

Data center applications are unlike their commercial building counterparts in two significant ways, he noted. First, they include significantly higher plug loads. And second, they employ rapidly changing technology for the IT equipment and associated power/cooling approaches.

“It has been acknowledged that these differences drive a fundamentally different approach to regulating minimum efficiency requirements for the electrical and mechanical systems that support the plug loads,” Quirk said. “By using an approach that requires compliance to a ‘system’ level of performance, designers and end-users can utilize various trade-offs in their optimization strategizes depending on their company-specific business models.”

There was also a recognition that current industry modeling tools do not possess all the necessary mathematical models to accurately and appropriately model data center HVAC and power design. As a result, demonstrating compliance to the 90.1 Chapter 11 or energy cost budget (ECB) approaches was deemed impractical, according to Jarnagin.

This new standard is based on the principles of power use effectiveness (PUE), as defined by The Green Grid. However, because PUE is an operational measurement metric, and this is a design standard, PUE terminology is not a technically accurate usage. The committee recognizes that language needs to be developed to relate the calculations of energy efficiency set forth in this standard to a total efficiency number, as well as to allow tradeoffs between electrical and mechanical elements. Suggestions from reviewers as to how best to accomplish this are welcome, he said.

Jarnagin said the two committees are aware of some potential conflicts between the definitions of computer rooms and data centers in the standards. The intent is to address those conflicts once Standard 90.4 is approved and published.

The proposed standard applies to new data centers and telecommunications buildings or portions thereof and their systems, new additions to data centers and telecommunications buildings or portions thereof and their systems, and modifications to systems and equipment in existing data centers and telecommunications buildings or portions thereof

To read the draft standard and submit comments, go to www.ashrae.org/publicreviews.

Publication date: 3/2/2015

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