This thesis contributes to Sustainable Interaction Design by exploring how an eco-feedback enriched design proposal may engage people to collectively reduce carbon emissions. Taking a participatory design approach, the project identified fashion consumption as an area of opportunity towards this aim and proposes a design concept as an alternative to resource and emission-intense consumption by engaging swapping and renting of fashion. Challenges found in field research with regard to re-using fashion were problematised, namely quality, trust and fairness. The project aimed to address these challenges by conceptualizing an engaging user experience that creates a community between people to share fashion with each other. Values and unique qualities of fashion were investigated as well as how visualizing the environmental impact of such activity affects user engagement. User testing suggests that such eco-feedback positively impacts engagement with the proposed concept.