The United States (U.S.) Department of Energy (DOE) conducted a final quantitative analysis to assess whether buildings constructed according to the requirements of the ASHRAE Standard 90.1-2007 would result in energy savings compared with buildings constructed to ASHRAE Standard 90.1-2004. The final analysis considered each of the 44 addenda to ASHRAE Standard 90.1-2004 that were included in ASHRAE Standard 90.1-2007. All 44 addenda processed by ASHRAE in the creation of Standard 90.1-2007 from ASHRAE Standard 90.1-2004 were reviewed by DOE, and their combined impact on a suite of 15 building prototype models in 15 ASHRAE climate zones was considered. Most addenda were deemed to have little quantifiable impact on building efficiency for the purpose of DOE’s final determination. However, out of the 44 addenda, 9 were preliminarily determined to have measureable and quantifiable impact.