Retrofitting older buildings will be a particularly important component of clean energy transitions, especially given the age of building stock and costs associated with inefficient use of energy. In the United States, around 60% of multifamily buildings were built prior to 1980 while over half of available rentals are estimated to be at least 50 years old. In particular, the small commercial apartment property market has been an especially challenging one for energy efficiency improvements due to ownership structures and knowledge gaps. In response, with support from the DOE’s Commercial Buildings Integration programme and funding from the Solution to Improve the Energy Efficiency of Small and Medium Buildings, the International Center for Appropriate and Sustainable Technology is expanding deep retrofits in the US small commercial property market. In particular, ICAST offers a platform of resources to owners of small commercial apartments to undertake retrofits, including green consultants to provide energy audits, financial consultants to provide financing advice, and implementation contractors. Using a one-stop-shop approach, ICAST in partnership with DOE completed energy efficiency upgrades on 956 multi-family buildings with eight affiliates across four states and seven cities. The completed project demonstrated an annual energy savings of 103 166 MMBtu, 190 298 GHG emissions reduced over the lifetime of the upgrades, 258 jobs created, and USD 4 008 average utility savings per building annually. In total, ICAST has successfully undertaken over 5 000 retrofits of multifamily homes.