uses no net purchased energy (a Zero Energy Building). The lower the value, the better. For capitalizing a building's energy performance in the mortgage loan, certification of “White Tags” for private financial investors, and by the US government for verification of building energy performance for such programs as federal tax incentives, the United States Environmental Protection Agency’s Energy Star program and the U.S. Department of Energy’s Building America Program. Derivative calculations include the RESNET-proprietary HERStm Index, which is modified by RESNET's MINHERS Standards. RESNET has publicly stated that the HERS Index modifies the ANSI Standards for their proprietary HERS Ratings. Additional ERI variants are modified by different iterations of the International Code Council (ICC) energy code. Typically differences include changes to mechanical ventilation. The HERS Index replaced the earlier "HERS Score", which ran in the opposite direction: The higher the value, the better. In 2009, the U.S. Department of Energy presented a new scale, the "EnergySmart Home Scale (E-Scale)", "based on" the HERS Index, apparently simply by subtracting the HERS Index from 100. In this new scale, higher values correspond again to better performance. As of March 2022, a Carbon Index measurement has been added to ANSI 301-2019 through Addendum D-2022. Projected and Confirmed Ratings Projected ratings give home owners and builders an estimate of what a home's estimated efficiency will be like after construction or improvements, so that they may determine the most cost-effective route to improve a building's efficiency. A confirmed rating, which indicates the home's as-built estimated efficiency, requires an inspection of the home from an energy rater. The energy rater reviews the home to identify its energy characteristics, such as insulation levels, window efficiency, wall-to-window ratios, the heating and cooling system efficiency, the solar orientation of the home, and the water heating system. Performance testing, such as a blower door test for air leakage and duct leakage, is usually part of the rating. Confirmed, Sampled, and Threshold Ratings are registered with public databases such as the RESNET Registry and the BSI Registry. Some confirmed ratings also extend an economic guarantee on energy usage. Types of Verifiers In order to provide certified Energy Ratings to rating clients such as builders or homeowners, individuals must become a Certified Rater through an Approved Rating Provider. Under RESNET's MINHERS, the process of becoming a Certified HERS Rater includes the following: Training: HERS Rater candidates shall attend a HERS Rater training