Pre-retrofit building performance evaluation of existing UK social housing dwellings

As part of the transition to Net Zero by 2050, the UK Government’s Social Housing Demonstration Fund has been launched to upgrade a significant amount of the social rented homes in England to an Energy Performance Certificate (EPC) Band C standard, while delivering warm, energy-efficient homes and tackling fuel poverty. This paper uses building performance evaluation (BPE) methods to empirically examine pre-retrofit building fabric thermal performance, energy use, indoor environmental conditions and household characteristics of 32 social housing dwellings located in Warwickshire, England. Empirical data was gathered between 1 December 2021 and 30 November 2022. Thermography revealed a lack of insulation, with significant heat loss around wall joints. This was more pronounced in the 1920s triangular semi-detached dwellings which had the highest gas consumption at 12,000kWh/year compared to 4,500kWh in the 1960s terraces. The average annual energy cost across the sample was £1,645, with a maximum of £4,320/year. Statistical analysis of time-series data revealed that the 1960s terrace typology experienced the lowest indoor temperature across all seasons due to less number of exposed sides. Summer indoor temperature was 4°C higher than other seasons, often exceeding 30°C. Relative humidity of 52% was relatively stable. The 1960s terraced dwellings experienced the highest diurnal CO2 levels with peaks exceeding 1400ppm during occupied hours. Peak CO2 concentrations reached 5000ppm with some daily averages over 3300ppm due to prolonged occupancy and inadequate window-opening to conserve heat. Since the dwellings overheated in the summer and were cold in the winter, an approach to retrofitting needs to combine building fabric and heating system upgrades with passive measures (shading, ventilation) for tackling overheating so that these homes can stay warm in winter and cool in summer. A data driven based approach to retrofit assessment and evaluation will also help in reducing performance gap.