This document is the Executive Summary of a broader Building Retrofit Industry and Market Development Project (BRIM-DP) launched in early 2010 to inform philanthropic investments in building energy retrofits (i.e., the application of energy efficient or clean generation measures to existing building stock). BRIM-DP was designed in three phases: 1) Phase I – Develop a Framework for Market Development; 2) Phase II – Create a Detailed Market Segmentation and Summarize Existing Market Research on Each Segment; and 3) Phase III – Develop Detailed Segment-Specific Strategies and Organize Key Stakeholders to Collaborate on National Investment Strategies. Phase I created a broad framework for a coordinated national strategy to develop the building retrofit market.