Addendum 66f amends the MINHERS® Chapter 3 to add criteria for the calculation and labeling of a CO2 Index. The addendum establishes criteria and identifies data for the calculation of the CO2 Index necessary for software providers to revise energy rating software to produce the new CO2 rating and to print it on the rating label. Development of the CO2 Index rating utilizes current Minimum Rated Features and does not require additional data to be collected by raters. An interim version of Addendum 66, (66i), has been adopted by RESNET to allow software providers to begin the revision of their software. The Mandatory Compliance Date for producing and reporting CO2 Index ratings will be established by the final version of the addendum, Addendum 66f, and will be coordinated with the availability of updated software. To review the draft addendum click on Draft PDS-01, MINHERS® Addendum 66f, CO2 Index To submit your comments, click on RESNET Amendment Comment Online Form for Draft PDS-01, MINHERS® Addendum 66f, CO2 Index Comments are posted in real-time and you will be able to review comments by clicking on Comments Submitted on Draft Draft PDS-01, MINHERS® Addendum 66f, CO2 Index The public comment period will begin February 18, 2022, and end March 20, 2022.