Detailed Textual Analysis of the Differences Between the 1989 and 1999 Editions of Standard 90.1

The Energy Conservation and Production Act provides that whenever the ASHRAE Standard 90.1-1989, or any successor to that code is revised, the Secretary of Energy must determine whether the revised code would improve energy efficiency in commercial buildings

The U.S. Department of Energy has performed both a quantitative analysis of the likely impacts of the revised code on the energy efficiency of seven categories of new commercial buildings, compared to the 1989 edition, and a non-quantitative assessment of the comparative stringency of those elements of the revised code that could not be analyzed quantitatively.

The quantitative analysis concluded that the1999 revision of the code would likely reduce the source energy consumption of new commercial buildings by approximately 5.9 percent. Site energy savings were estimated to be approximately 3.9 percent. The comparative assessment of those elements of the 1989 and 1999 revised codes that could not be quantitatively analyzed also concluded that the 1999 standard would increase energy efficiency.