Domestic retrofit is commonly framed as a technical optimisation challenge or as a market-activation problem addressed through incentives, information, and finance. This paper argues that such framings systematically understate the political, ethical, and relational dimensions of dwelling, and consequently undermine legitimacy, inclusion, and long-term performance. The paper therefore reframes domestic retrofit as ecological citizenship, understood as a civic and everyday practice through which households participate in shared socio-ecological care and negotiate rights, responsibilities, risks, and benefits with institutions, communities, and supply chains. The study addresses three research questions: (1) What design and governance conditions are required for retrofit to be conceived and organised as civic infrastructure rather than a consumer service? (2) Which generative mechanisms enable retrofit pathways to produce trust, inclusion, and legitimacy across diverse households and housing types? (3) How can national and local delivery models be coherently aligned to achieve both contextual fit and scalable impact? Methodologically, the paper combines design ethnography, participatory workshops, and speculative prototyping with realist evaluation and contribution analysis. Empirically, the argument is developed through three contrasting case studies: ROSSY/YorEnergy, a municipal one-stop shop that positions retrofit as a public service; Wildhouse, an experimental retrofit that foregrounds more-than-human dwelling through bio-based materials, biodiversity features, and sensory feedback; and AgLab, a distributed farm-led model that links retrofit to material commons and regenerative local economies. The analysis identifies eight recurring mechanisms that shape retrofit outcomes across contexts: institutional trust, contextual fit, friction minimisation, finance intermediation, supply-chain co-production, demonstration effects, governance agility, and equity-by-design. Together these mechanisms extend conventional definitions of success beyond installation counts and carbon metrics towards the capacity of retrofit systems to reach, activate, convert, and retain households in staged, coherent, and socially just journeys. The paper contributes (1) a theoretical reframing of retrofit as ecological citizenship, (2) a pattern language of designable defaults for civic retrofit infrastructures, and (3) a federated delivery model described as “national rails and local doors”, aligning national standards and capital with local legitimacy and delivery capacity. It concludes that retrofit should be treated as civic infrastructure in which design mediates between policy, materials, institutions, and everyday life, and that fail-to-safe institutional patterns are essential to just, durable, and scalable decarbonisation.