This research focusses on practical difficulties and cost-effective solutions found in Passivhaus refurbishment projects in the UK. From analysing working details bespoke questionnaires were developed for contractors and architects directly involved. The primary aim was to find best practice taking into account the theoretical difficulties of assessing condensation risk and thermal bridging. Best practices were defined by the level of difficulty in constructing the detail solution and the cost-effectiveness of the techniques in terms of labour, materials and thermal performance. An overview of the technical background is followed by four main case studies. The appendices go into depth with three other projects and specific problems encountered during their build processes. The appendices include a wealth of information, exploring thermal bridging and condensation risk. The research is intended to provide a sense of practical possibility for refurbishing dwellings to high levels of energy efficiency. A report based on this research won the CIAT Student Award for Excellence in Architectural Technology (Technical Report) 2012.