The first element is a modeling-based analysis of the costs, benefits, technical options, and key challenges specific to the Existing Homes Initiative, and of the associated impacts. [...] Project Approach The first element of this project is a modeling-based analysis of the costs, benefits, technical options, and key challenges specific to the Existing Homes Initiative, and of the associated impacts. [...] Project Approach The first element of this project is a modeling-based analysis of the costs, benefits, technical options, and key challenges specific to the Existing Homes Initiative, and of the associated impacts. [...] Project Approach The first element of this project is a modeling-based analysis of the costs, benefits, technical options, and key challenges specific to the Existing Homes Initiative, and of the associated impacts. [...] Project Approach The first element of this project is a modeling-based analysis of the costs, benefits, technical options, and key challenges specific to the Existing Homes Initiative, and of the associated impacts.