To support sustainability transitions several different design approaches are required. In a series of Designerly Living Labs, we have prototyped possible sustainable futures in the context of people’s everyday lives to explore the complexities of lifestyle changes and socio-technical system shifts. Together with users engaged as reflexive co-researchers, we have explored potential new practices and uncovered system-level tensions and deficiencies. System changes have been initiated by engaging relevant actors in learning processes and by bridging learning to decision-makers. However, the approach requires some rethinking of design as a practice. Instead of supporting people’s current needs and lifestyles, we design for sustainable futures that users do not yet request. This emerging design practice challenges traditional co-design and user participation methods, leading to new ethical considerations.