This study seeks to update and expand the quantification of greenhouse gas emissions and other co-benefits associated with building green homes in California. The research herein aligns with the GreenPoint Rated Climate Calculator that is administered by Build It Green, a California non-profit organization. Version 1 of the Climate Calculator, first created in 2009, is the most comprehensive single-building quantification tool for green homes in the country. The Climate Calculator relies on independently verified green building standards set forth in GreenPoint Rated, which exceed minimum code provisions for California. The goals of this research were to review and update Version 1 of the Climate Calculator based on new research; to test and compare results from Version 1 and Version 2 of the Calculator on actual homes; to expand the quantification metrics beyond the original scope where feasible; and provide a free online version of the Climate Calculator to the public. As a result of this work, Version 2 of the Climate Calculator now includes several important peer-reviewed strategies that more accurately measure the benefits of building and renovating green homes. A public version of the Calculator that is informed by this research is forthcoming.