Measures, benefits, and challenges to retrofitting existing buildings to net zero carbon: A comprehensive review

Net zero carbon (NZC) retrofitting of existing buildings contributes to improving occupants' well-being, addressing carbon footprint directly and is key to solving the global climate crisis. However, a fragmented NZC retrofit knowledge base exists and this challenges the ability to effectively implement NZC practices. This study, therefore, integratively and comprehensively reviews existing literature on NZC retrofitting of existing buildings and identifies research gaps to provide future research directions. Bibliometric analysis was conducted using 1544 relevant articles identified from Scopus. Moreover, based on 125 carefully selected articles, a further qualitative analysis was also conducted. Results indicated a gradual increase in interest in NZC retrofitting research since 2007. Emergent findings reveal that the UK, Italy, US, China and Spain are the top five countries in this research field and that in NZC retrofitting, energy is mostly prioritised. Key research themes include NZC retrofitting benefits, challenges and measures. Based on identified knowledge gaps, future research directions are proposed to include: (1) analysis of NZC retrofitting measures based on building types and climate conditions; (2) integration of NZC retrofitting measures; (3) effects of occupants' health, well-being and satisfaction on retrofitting; (4) integration of modern technology; (5) quantitative study on benefits; and (6) dealing with objections to NZC retrofitting. Emergent findings generate an in-depth understanding of the NZC retrofitting field and provide a useful milestone reference for future NZC retrofitting practice and improvement in the industry.