Building Energy Efficiency: ASHRAE’s Economizer Requirements and the Effect on Facilities

Within the year, ASHRAE 90.1 – 2010, the new energy standard for buildings, will become part of commercial building codes in the US. The new standard contains many changes from the 2007 edition that will affect the design, construction and operation of buildings.

One important change is that a cooling system with a cooling capacity of greater than 54,000 Btu/h must have an air economizer or a water economizer.

The only areas exempt from following the economizer requirement are the southernmost tip of Florida and some southern parts of Arizona because the climates in these areas are not favorable for economizing, according to the James M. Pleasants Company (JMPCO), a manufacturer of products and solutions for energy efficient water and steam systems.

The standard will significantly impact cooling design, says JMPCO. This is the first time a change in standards has modified building codes to essentially mandate economizer sizing requirements.

Water economizer systems must cool the air supply by indirect evaporation and satisfy as much as 100% of the system cooling load when outdoor air temperatures are 50 degrees Fahrenheit dry bulb/45 degrees Fahrenheit wet bulb or lower.

Because of this requirement, engineers will have to size water economizers to handle the building load whenever outdoor temperatures are at 50 degrees Fahrenheit dry bulb/45 degrees Fahrenheit wet bulb or lower.

Response to the change in the standards has not been 100% positive.

When the change to the standards was originally proposed, a group of executives from Microsoft, Google, Digital Realty Trust, Amazon, DuPont Fabros Technology and Nokia issued a statement opposing the change for data centers, according to Data Center Knowledge. In the statement, the group urges the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to favor performance-based efficiency goals for data centers over economizers.

“We believe that for data centers, where the energy used to perform a function (e.g., cooling) is easily measured, efficiency standards should be performance-based, not prescriptive,”and “In other words, the standard should set the required efficiency without prescribing the specific technologies to accomplish that goal,” the group says in the statement.

“In many cases, economizers are a great way to cool a data center (in fact, many of our companies’ data centers use them extensively), but simply requiring their use doesn’t guarantee an efficient system, and they may not be the best choice,” the group adds.

The group says the standards should not limit the cooling methods to economizers because it believes other cooling methods could achieve the same or better results.

“An efficiency standard should not prohibit such innovation,” the group notes.

To see your state’s current adoption status of the new standards, visit www.energycodes.gov.

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