Longitudinal Assessment of Indoor Environment in Existing UK Social Housing Dwellings in Need of Energy Retrofits

Existing conditions in the UK social housing sector are recognised as being undesirable, yet there is a lack of empirical evidence on the indoor conditions experienced by social housing residents, who are often physically and/or financially vulnerable. This paper presents a longitudinal empirical study that measured indoor temperatures, relative humidity (RH), and CO2 levels in the bedrooms of 23 social housing dwellings in Warwickshire (UK) over two winters - 2021/22 (season 1) and 2022/23 (season 2), while particulate matter (PM)(2.5), PM10 and volatile organic compounds (VOCs) (Isobutylene and EtOH) were measured in a sub-sample of 13 living rooms. Mean indoor temperatures were observed to be lower in season 2, by 0.7 degrees C in living rooms (from 19.2 degrees C in season 1 (range: 9.2-28.1 degrees C) to 18.5 degrees C in season 2 (range: 8.7-24.5 degrees C)) and by 1.9 degrees C in bedrooms (from 19 degrees C in season 1 (range: 11.6-27.6 degrees C) to 17.1 degrees C in season 2 (range: 4.1-26.4 degrees C)), indicating a reduction in heating energy use possibly as a response to energy price rise in 2022/23. The majority of monitored living rooms and all 23 bedrooms experienced high levels of CO2, exceeding the recommended limit of 900 ppm for >95% of occupied hours in both seasons. Living rooms experienced mean CO2 levels of 1,193 ppm in season 1 against 1,519 ppm in season 2, with maximum values reaching up to 5,000 ppm across both seasons. Prolonged occupancy with limited ventilation to retain heat was widespread. High levels of VOCs matched with personal activities such as the use of air fresheners and cleaning products, indicating poor ventilation. Planned energy retrofits of these dwellings should consider insulation alongside ventilation to ensure occupant health and well-being.