Now that durable alternatives to energy from fossil sources have become technologically and economically feasible, the challenge of the energy transition is primarily one of mobilizing populations to act. Here we study the mobilizability of Dutch rental flat residents for sustainable energy alterations to their homes. We argue that the structure of the social network among residents will greatly affect its ability to spread information on energy alternatives and propagate cascades of green adoption behavior. Using a survey circulated in a rental flat in the Dutch city of Haarlem, we were able to map the social network of its residents and assess their willingness to incur costs and discomfort for uncertain future gains. Our analysis reveals a surprisingly cooperative population of low-income residents and a remarkably integrated network structure showing no sign of ethnic or religious segregation.