Ruiyang Huang

Optimising fabric-first retrofit strategies to improve housing resilience in Belfast

In 2023-34, 2.9 million households in the UK reported that their homes were uncomfortably hot under heatwaves. 3.2 million households claimed that their homes were unable to keep warm during winter. Increasing frequency of extreme climate events is projected to worsen episodes of poor thermal comfort in homes, leading to more frequent periods of indoor overheating and cold stress. With 80% of existing dwellings expected to remain in occupancy in 2050, improving residential energy performance through domestic retrofit is a critical strategy for enhancing climate resilience. Fabric-first retrofit is a mainstream approach of minimising the impact from global climate change as it improves the thermal performance of building envelope. Moreover, it reduces energy demand and therefore the carbon emissions, contributing to wider mitigation efforts to reduce the trend towards more extreme, frequent events due to the changing climate. However, there remains existing research gaps when analysing the interaction between retrofit measures. Most of research considered multiple retrofit measures as a package, making it tricky to visualise the performance gain from each measure individually. Also, marginal effects of retrofit measures at different levels are rarely mentioned. Moreover, when analysing the cost effectiveness, too much focus is often given to the goals of decarbonisation and financial investment return, with indoor thermal comfort less assessed. This dissertation investigates the interaction between two key fabric-first measures -glazing upgrades and wall insulation installation, in the context of Belfast, Northern Ireland, a region with one of the lowest retrofit funding availabilities in the UK. Using DesignBuilder software, a typical two-up-two-down terrace is modelled to simulate various retrofitting scenarios. The study conducts a parametric analysis on different combinations of glazing and insulation retrofit measures, evaluating their effects on thermal comfort improvement (measured in discomfort hours decrease) and heating load reduction. The ratios between thermal comfort improvement and total retrofit costs are calculated to compare the cost efficiency of each combination. The heating load reduction can further indicate annual energy bill savings, which can calculate the measures’ payback period based on their initial installation costs. Moreover, the retrofitting scenarios are assessed under projected climate conditions to verify their effectiveness to tackle global climate change and secure housing resilience. The results indicate that there exists a synergistic relationship between wall insulation and glazing upgrade. Also, retrofit guidance should follow the principle of CWI first, EWI for overheating-prone or high WWR dwellings, and IWI where exterior moisture risk exists, while triple glazing should be avoided due to its low rate of return.