Review on building retro-commissioning: a systematic-cascade literature analysis with expert validation

To optimize the energy performance of buildings, governments worldwide have introduced retro-commissioning (RCx), a systematic investigation of opportunities to improve the performance of existing buildings. However, RCx studies and applications are not as prevalent as those in the other building energy related domains. The past and recent states of RCx research have not been thoroughly investigated, and future research directions remain unclear. Therefore, a review is conducted to address these gaps using a systematic-cascade approach that includes: retrieval of RCx publications from the ScienceDirect and Scopus databases; bibliometric analysis of the publications using the VOSviewer software; in-depth qualitative analysis of key RCx publications and real case studies; and expert validation of the analysed findings. Key results include the identification of the regions of the past RCx studies, types of buildings and building systems investigated, data types, and data collection and analysis methods used in the studies. Distinct from the continual growth of research in the building energy domain, there was no discernible trend of RCx research. Among the past studies utilizing empirical data, universities and schools are mainly selected for testing RCx scenarios or hypotheses. Barriers and enablers for RCx implementation were found to fall into six categories: knowledge, manpower, finance, motivation, time, and data/information. Nine research gaps and corresponding future research directions were also identified. In addition to contributing to the existing body of RCx knowledge, the results of this study serve as a reference for RCx stakeholders and offer guidance for researchers to pursue further RCx studies.