Renewable Energy or Energy Efficiency? Building Occupant Preferences toward Net Zero Carbon Retrofit Measures

One of the most important targets the world aims to attain is net zero carbon (NZC) by 2050. To achieve this target, there is an urgent need for NZC retrofits in existing buildings, as they account for 37% of global carbon emissions. While previous studies have assessed the energy consumption, carbon emissions, and costs of retrofit measures, there is a lack of knowledge on building occupant preferences toward NZC retrofit measures. Therefore, the intention of this study is to assess the preferences of building occupants in Hong Kong regarding NZC retrofit measures for existing residential buildings. Following a comprehensive literature review to identify NZC retrofit measures, a questionnaire survey was performed with 123 building occupants. The mean score ranking method was used to analyse the data. Results indicated that most building occupants prefer renewable energy upgrades to building envelope and energy system (energy efficiency) upgrades in the retrofit of their buildings. This result is surprising as many global NZC standards recommend always prioritizing energy efficiency. In addition, this study further analysed building occupant preferences for individual retrofit measures under renewable energy sources and changes to building envelope and energy systems. Thus, this study expands the existing theoretical understanding of NZC retrofitting measures through an assessment of their efficacy in accordance with occupant preferences. Further, this study provides significant information for policymakers and industry practitioners, aiding in the application of retrofit measures necessary to attain NZC buildings.