The applicability of stepwise retrofitting in the Australian residential sector: an exploratory qualitative study

Purpose Stepwise retrofitting offers a phased, flexible approach to improve building energy performance and overcome the financial and logistical barriers of single-step retrofitting. However, existing research relies on theoretical models and simulations, often overlooking real-world market conditions. This study investigates the practical applicability of stepwise retrofitting in the Australian residential sector, drawing on insights from experts. Design/methodology/approach An exploratory qualitative research design was employed. The data were collected through 11 expert interviews with industry, policy, and academia, followed by triangulation with a policy analysis. Thematic analysis and directed content analysis were conducted to analyse insights under three core elements of stepwise retrofitting: timing, packaging, and sequencing. Findings Experts recommend mandated 10-year retrofitting cycles with retrofit steps spaced every three years. This study proposes, for the first time, a hybrid retrofit package approach that combines standardised measures (e.g. insulation, glazing) and customised audits for complex systems (e.g. HVAC). A structured three-step retrofit sequence is recommended: (1) basic envelope improvements, (2) targeted upgrades, and (3) advanced technology integration. Research limitations/implications Since the study is confined to expert interviews, future studies should focus on conducting longitudinal case studies once the stepwise retrofitting is industrialised. Originality/value The study establishes a foundational guideline for timing, packaging, and sequencing (see Table 4) and contextualises the guideline within the existing Australian policy landscape (see Table 5). This study presents a novel sequencing approach for stepwise retrofitting and introduces a first-of-its-kind application framework for stepwise retrofitting, providing a skeleton for smart home researchers to build upon (see Figure 4).