Contemporary housing systems neither live up to their social nor their ecological aims, resulting in affordability and environmental crises. We explore the potentials for securing access to affordable and adequate housing for all while rapidly reducing energy and resource use and associated greenhouse-gas (GHG) emissions. For this purpose, we carry out a case study of the housing system in Vienna to scrutinize how social-ecological provision has been enabled or restrained by Viennese housing regulations. We introduce a broad conceptualization of housing that encompasses material objects (housing as noun) and socio-cultural practices (housing as verb) and embed these concepts in a provisioning perspective. The history of Vienna’s housing system is outlined with an emphasis on the radical municipal reformism of Red Vienna (1919–1934) and path dependencies from welfare capitalism to neoliberalism. Based on the historical analysis, we highlight barriers hindering social-ecological housing provision today and suggest three sets of measures for greening Red Vienna: (1) Establishing social-ecological obligations to property ownership, prioritizing ecological upgrading, and favoring retrofitting instead of new constructions; (2) introducing lower and upper limits on housing provision to reduce inequalities; and (3) overcoming the focus on individual building sites and widening the scope of housing policies toward securing habitation for all residents.