Systematic review: Upscaling energy retrofitting to the multi-building level

Retrofitting the building stock is pivotal to achieving climate neutrality by 2050. Most of the existing research on energy efficiency focuses on new residential buildings. The focus must shift to multi-building retrofits, thereby more frequently including non-residential buildings. As multi-building and non-residential projects are given a lighthouse role in achieving current global climate goals, more research should focus on this potential. This study covers single- and multi-building retrofitting projects. It also explores the role of non-residential projects, typical project settings, energy reduction achievements and the added complexity of the multi-building scale. The chosen methodology combines a systematic literature search with a subsequent critical metadata and full-text review of more than 80 peer-reviewed scientific papers. The results show that the number of studies in the research field has increased substantially in the last few years, while the research mostly originates from Europe and focuses on the residential building typology. This research is partly transferable to similar climate zones elsewhere, while a large proportion of climate zones remains unexplored. The current body of definitions and requirements regarding energy retrofitting is an impediment to the comparability of projects, and particularly the multi-building scale is in need of international guidance. Future research should focus on making retrofit measures more applicable internationally, while unifying project boundaries. The stronger inclusion of non-residential retrofitting projects as lighthouse projects including social aspects is needed. Retrofitting that covers energy production and sharing has great potential and should be seen as an opportunity.