Domestic retrofitting is the process of adding new features, components, or technology to an existing residential building to improve its sustainability - including performance, energy efficiency, safety, functionality, and comfort. This is done by upgrading older structures to meet modern standards, such as improving insulation, replacing windows, installing new heating systems, and reducing energy consumption to lower utility costs and environmental impact. The issue of domestic retrofit has presented itself as a "wicked problem". The complex inter-relationships between policy, skills infrastructure, supply chains, finance, markets and other socio-technical issues, have made the policy difficult to formulate and implement. Expertise needs to stretch across technical subjects such as building physics and data analytics, through delivery issues such as skills and supply chain, to understanding the outcomes for people in their homes.Concepts, Methodologies and Technologies for Domestic Retrofit addresses three main themes: enabling retrofit, delivering retrofit and evaluating retrofit. Enabling retrofit looks at the context for delivering retrofit and understanding the structures that need to be in place to deliver the necessary upscaling. This considers place-based approaches, finance models, target setting and understanding how to develop a pipeline, particularly in harder to reach sectors such as the private rented or owner occupier sectors. Delivering retrofit considers the processes that lead to a high-quality retrofit. Effective assessment, quality systems, technical choices and the development of supply chains, all underpin an effective delivery system. Finally, the authors consider evaluation of retrofit. New methods and access to data have changed the way retrofit is understood in terms of real performance, so the authors discuss the current state of the art and emerging approaches. The outcomes are not purely technical; the impacts for people in their homes and how they have viewed retrofit are also considered, not only in terms of energy saving, but also their comfort and health.The book is targeted not only at an academic audience, but also practitioners and policy makers. It aims to provide clear practical guidance, linkages to the latest thinking and practice and a practical perspective on the problems and opportunities presented by domestic retrofit.