Recent analysis by the U.S. Department of Energy (DOE) shows that buildings meeting a 2010 energy efficiency standard will use 18.5 percent less energy than those using the 2007 version of the standard, helping commercial building owners cut operating costs.

According to the DOE report, “Energy Standard for Buildings, Except Low-Rise Residential Buildings,” the new version of Standard 90.1 will also help building owners achieve sustainability goals and reduce carbon pollution. States must update their building codes to meet or exceed the energy efficiency of the new standard within two years, with certification statements due on October 18, 2013.

Standard 90.1-2010 contains 19 requirements for energy efficiency, including the following: cool roofs in hot climates; skylights and daylighting in certain building types; daylighting controls under skylights; commissioning of daylighting controls; increased use of heat recovery; supply air temperature resetting for non-peak conditions; lower lighting power densities; control of exterior lighting; occupancy sensors for specific applications and efficiency requirements for data centers.

Some changes in the standard were the result of public comments. DOE analyzed energy codes published by the American National Standards Institute/American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) and the Illuminating Engineering Society of North America to determine potential energy-efficiency savings in buildings that adhere to the code. DOE simulated 16 representative building types, ranging from single-family homes to the world’s largest buildings, in 15 U.S. climate locations.

Varying results

Comparing hypothetical buildings constructed to the old standard to the same buildings constructed to the new standard is “a lot like MPG ratings for cars—results will vary with actual use,” says Robert Diemer, director of In Posse, a national environmental consulting firm, headquartered in Philadelphia, focusing on sustainable design in a wide range of market sectors.

DOE’s assessment is consistent with the usual result of design team and building owners working together to implement best practices in energy-efficient design following the standard, says Michael Gresty, executive vice president of Sustainability Roundtable Inc., a Cambridge, Mass.-based research and consulting firm focused on the development of sustainable business practices.

However, he adds, for Standard 90.1-2010 to improve a structure’s energy efficiency, “it is essential that the project be commissioned and be operated and designed.”

Time will tell

Although the impact of each updated standard usually takes years, notes Matthew Dugan, president of DVL Automation, a Philadelphia-based HVAC system integration firm, the U.S. Green Building Council (USGBC) is accelerating the impact of this standard ahead of building codes by basing the 2012 version of LEED criteria on the ASHRAE 90.1-2010 version.

“This represents the next step in our evolution towards impacting global climate change,” Dugan says, “with the reduction of U.S. building stock from its current average of 91 KBTU [Kilo British Thermal Units] per sq. ft. per year to our interim goal of 47 KBTU per sq. ft. per year by 2030.”

Possible pushback

Each time ASHRAE Standard 90.1 is updated, “the bar is raised and we have to work harder to generate equivalent savings,” says Diemer. Not only must states comply by updating building codes, but equipment manufacturers are forced to improve the performance of their products to meet increasingly more stringent efficiency thresholds.

However, Diemer believes the impact of adopting each new standard falls mostly on building design professionals, who must undergo a learning curve as well as potential pushback from commercial building developers over the need to add additional costs to account for new requirements, such as mandatory daylight harvesting in certain situations.

Dugan notes that state building codes no longer adopt ASHRAE standards by “reference,” and instead simply select portions they choose to “edit” or “copy.” While he expects code officials to align with the new standard, he says he is concerned that “several of its elements reach into new areas of influence—in particular, the scope of the standard has been expanded to include process loads, e.g. data centers, and receptacles.”

Going further?

The 2007 version of Standard 90.1 has actually already been surpassed by ASHRAE 189.1, Gresty points out. According to an estimate by the National Renewable Energy Laboratory (NREL), “Standard 189.1 could lead to site energy savings between 10 percent and 34 percent over Standard 90.1-2007, based on the minimum prescriptive recommendations of the new standard—and possibly even higher, since further energy-saving measures were incorporated after the NREL inquiry,” he says.

Because the standard only results in theoretical improvements rather than real and absolute performance improvements, says Diemer, “the impact on actual building energy use is most likely less than assumed by DOE’s analysis of findings.”

He would prefer to see the standard require “actual, documented energy performance rather than allow for prescriptive compliance or calculated theoretical savings.”

Although Diemer recognizes that such an approach isn’t practical or politically feasible, he believes that requiring disclosure of actual energy performance could have an impact on building performances exceeding Standard 90.1, because “such measures could be applied to all buildings, not just those requiring building permits or LEED certification.”

Energy disclosure requirements are starting to be put into place at state and local levels—including in Austin, Texas; Boulder, Colo.; New York City; Chicago and Washington, D.C.—and are currently under consideration in Philadelphia, says Janet Milkman, LEED Green Associate and executive director of the Delaware Valley Green Building Council. Milkman says her organization is “supporting these requirements as a strong measure to drive the market for energy-efficiency applications.”