This paper discusses the results of five case studies of dwellings in Swansea, UK, that received retrofitted external wall insulation through the first phase of the Welsh government's 'Arbed' scheme in Wales between 2010 and 2012.Arbed is part of the Welsh government's carbon dioxide emissions reduction and fuel poverty policy objectives.Energy consumption, costs and carbon dioxide emissions data are presented and discussed for each case study, which were collected as part of a doctoral research project undertaken in collaboration with two housing associations in Swansea, Wales. These data are analysed to assess alleviations of fuel poverty, reductions in carbon dioxide emissions and the payback of the interventions. Furthermore, unintended benefits and the implications for further dwellings receiving external wall insulation are also discussed. This paper will be useful to stakeholders involved in the upgrade of existing buildings built around 1919 in reviewing options that give the best payback against energy and carbon dioxide emissions savings.