This document presents the qualitative comparison of DOE’s formal determination of energy savings of ANSI/ASHRAE/IESNA Standard 90.1-2004. The term “qualitative” is used in the sense of identifying whether or not changes have a positive, negative, or neutral impact on energy efficiency of the standard, with no attempt made to quantify that impact. A companion document will present the quantitative comparison of DOE’s determination. The quantitative comparison will be based on whole building simulation of selected building prototypes in selected climates. This document presents a comparison of the energy efficiency requirements in ANSI/ASHRAE/IESNA 90.1-1999 (herein referred to as Standard 90.1-1999) and ANSI/ASHRAE/IESNA 90.1-2004 (herein referred to as Standard 90.1-2004). The comparison was done through a thorough review of all addenda to Standard 90.1-1999 that were included in the published ANSI/ASHRAE/IESNA Standard 90.1-2001 (herein referred to as Standard 90.1-2001) and also all addenda to Standard 90.1-2001 that were included in the published Standard 90.1-2004. A summary table showing the impact of each addendum is provided. Each addendum to both Standards 90.1-1999 and 90.1-2001 was evaluated as to its impact on the energy efficiency requirements of the standard (greater efficiency, lesser efficiency) and as to significance. The final section of this document summarizes the impacts of the various addenda and proposes which addenda should be included in the companion quantitative portion of DOE’s determination. Addenda are referred to with the nomenclature addendum 90.1-xxz, where “xx” is either “99” for 1999 or “01” for 2001, and z is the ASHRAE letter designation for the addendum. Addenda names are shown in bold face in text. DOE has chosen not to prepare a separate evaluation of Standard 90.1-2001 as that standard does not appear to improve energy efficiency in commercial buildings. What this means for the determination of energy savings for Standard 90.1-2004 is that the baseline standard for comparison is Standard 90.1-1999 and all addenda to both Standards 90.1-1999 and 90.1-2001 must be considered to determine the overall change in efficiency between Standard 90.1-1999 and Standard 90.1-2004.