Engineered Systems Magazine

Revised ASHRAE Standard helps compare building energy performance

March 26, 2014

When it comes to measuring a building’s energy use, there is a lot to take into consideration. Are the measurements of a building’s area to be taken from the exterior dimensions or to the centerline of the wall? Since they are normally unoccupied, are storage spaces to be included or not? A revised standard from ASHRAE is aiming to answer those questions.

The newly revised ANSI/ASHRAE Standard 105-2014, Standard Methods of Determining, Expressing, and Comparing Building Energy Performance and Greenhouse Gas Emissions, supports commonality in reporting the energy performance of existing or proposed buildings to provide a consistent method of measuring, expressing, and comparing the energy performance of buildings.

“A standard method of measurement is needed in order to be able to compare one building's energy use to another,” said Keith Emerson, chair of the Standard 105 committee. “For instance, comparing one building's summer energy use to another building's winter use would be comparing apples and oranges.”

According to Emerson, the new edition of Standard 105 now includes procedures for going beyond site energy to calculate the impact of building energy use on primary (source) energy and greenhouse gasses.

It also provides a common basis for reporting building energy use in terms of delivered energy forms and expressions of energy performance; for comparing design options; and for comparing energy performance in terms of energy resources used and greenhouse gas emissions created, both across buildings and for energy efficiency measures within buildings.

“To keep the standard flexible, a number of decisions are left to those who adopt it, including what should be calculated beyond site energy and the multipliers for those additional calculations,” Emerson said.

Primary energy and greenhouse gas equivalence conversion factors have been left to the discretion of the adopting agencies and authorities, which are available from a number of sources, including an appendix in the standard. The standard has also been upgraded to code enforceable language.

To order or for more information, visit www.ashrae.org/bookstore.