The development trends of existing building energy conservation and emission reduction—a comprehensive review

The energy conservation of existing buildings plays a significant role in reducing global carbon emissions and building energy consumption. The research on building energy conservation focuses on discussing existing and new buildings. However, the research on energy conservation of existing buildings is relatively single, and there is a lack of systematic and in-depth review. Based on the bibliometric and qualitative analysis methods, this study selects the relevant literature from 2008 to 2022 for network mapping analysis and summarizes the research results. The seven indicators of impact factor, total publications, average publication year, total/average citations, and total/average normative citations were selected to analyze the selected articles by country, institution, journal, keywords, and highly cited literature. Three major research themes of existing building energy efficiency are obtained by analyzing the quantitative results of keywords and highly cited literature: (1) influencing factors and energy-saving obstacles of energy consumption, (2) energy-saving measures, and (3) energy-saving optimization and its evaluation method. Finally, based on the bibliometric results, this research qualitatively analyzes the highly cited literature and the latest research results to obtain the future development trends and possible directions of energy conservation in the existing buildings throughout their life cycle. This study provides innovative ideas for the energy-saving renovation of existing buildings: (1) Technology empowerment (using renewable energy, negative carbon technology, “artificial intelligence + Internet of Things + 5G” and cogeneration, etc.) and (2) Formulating regulations and policy incentives for different decision-makers (implementing demand response strategies such as time-of-use pricing to guide and restrict user behavior, considering carbon tax and carbon trading, etc.). on the premise of utilizing renewable energy and increasing the capacity resilience of the distribution grids, the existing buildings will be energy-efficient, economical, intelligent and comfortable in the future.