Essential parameters in stepwise retrofitting for long-term emission reduction in residential buildings

Stepwise retrofitting is significant for sustaining thermal comfort and energy efficiency in residential buildings long-term. However, existing models on stepwise retrofitting have ignored the social parameters while overlooking the temporal variations of many parameters. Thus, the study aims to investigate essential temporal parameters for timing stepwise retrofitting to maximise long-term emission reduction in existing residential buildings. The parameters were identified across environmental, technical, social, and economic categories through a comprehensive process, which included a desk study and nine expert interviews, followed by a thematic analysis. The findings revealed the applicability of novel parameters for stepwise retrofitting, including temporal variations of embodied and operational emissions, minimum call-out fee, market value, homeowner willingness, and point of sale, rental, and refurbishment intervals. Practitioners can use the determined parameters for long-term emission reduction through stepwise retrofitting, following validation in real case studies. These parameters will assist in developing a comprehensive dynamic model to estimate the optimal timing between steps in stepwise retrofitting, maximising long-term emission reduction.