Building retrofit for energy and carbon reduction: identifying future research priorities and trends from a critical analysis and systematic mapping review of the global literature

Retrofitting buildings is essential for climate change mitigation and has numerous co-benefits; however relatively little is known about effective retrofit for energy and carbon reduction. The UN Buildings Breakthrough Agenda therefore calls for research priorities and knowledge gaps to be identified (UN, 2023). While previous reviews have identified key trends in existing research, none has systematically analysed the full research picture and clearly identified research gaps and priorities. This paper responds to this urgent call, offering the most comprehensive analysis to date of current quantitative retrofit research through a systematic mapping review and critical meta-analysis of 1,058 abstracts of peer-reviewed articles from 2017-2024. The analysis identifies three significant and critical gaps for the first time. First, only 2% of papers consider future climates. As the climate is already changing, this is of major significance and should be an urgent focus for retrofit research. Second, only 10% of papers analyse real-world projects, despite awareness that models offer limited understanding of real energy-use in existing buildings. Third, while embodied impacts are increasingly accepted as critical for new buildings, they are considered in under a third of retrofit papers, resulting in unmeasured carbon emissions from retrofit. This paper recommends that further studies should be prioritised on: whole life impacts of retrofit; real-world case studies of renovation; and, perhaps most critically, the understanding of appropriate retrofits for already-changing climates. In order to support progress in this essential and urgent field, the comprehensive dataset of categorised studies is provided alongside the paper.