With growing concerns over energy and heat-related mortality/morbidity rates, enhancing building performances is key to improving the health and well-being of building occupants while reducing CO₂ emissions, in line with the UK Government’s Net-Zero targets. This study investigates the impacts of different retrofitting scenarios on overheating risk and energy performance in social housing for current and future climate conditions. Dynamic thermal simulations were carried out using Design Summer Year (DSY) weather files in DesignBuilder software for selected case study buildings. Winter performance was analysed using the Predicted Mean Vote (PMV) index, while summer results were assessed according to the Chartered Institution of Building Services Engineers Technical Memorandum 59 (CIBSE TM59) guidelines. The findings revealed that bedrooms, especially those facing south, were at high risk of overheating. Factors such as building construction, the number of exposed surfaces, and window area influenced the risks. External wall insulation outperformed internal wall insulation in improving summer comfort. In the winter, Passivhaus standards with natural ventilation ensured thermal comfort across all zones, with a 41–53% reduction in heating energy consumption under current weather conditions. The risk of overheating and associated health issues significantly increased for the future weather scenarios. Further investigation into ventilation strategies, occupant behaviour, and passive design is required to mitigate overheating risks while reducing energy consumption in buildings.

Purpose: This study investigates the interplay between Indoor/Outdoor Air Quality (IAQ/OAQ), occupant behaviour, and building Air Permeability (AP) aiming to identify the key Indoor Air Pollutants (IAPs) and develop effective mitigation strategies to simultaneously address energy efficiency, IAQ, and occupant health in social housing. Design/methodology/approach: A mixed-method approach was applied across social housing case study dwellings in the London Borough of Newham. Physical monitoring of PM10, PM2.5, CO, CO2, TVOCs, temperature and humidity was conducted using data loggers in three phases of (1) baseline conditions, (2) air purifier intervention and (3) behavioural interventions. CONTAM multizone modelling was adopted to assess indoor/outdoor air pollutant correlations and dispersion at four AP levels (1, 5, 10 and 15 m3/m2·h@50 Pa), while occupant behaviour and behavioural interventions were assessed through questionnaire surveys. Findings: Daily average pollutant levels, particularly for CO and TVOCs, significantly exceeded the WHO and CIBSE guidelines (by up to 16 and 57 times, respectively), largely driven by occupant activities. Air purifiers reduced PMs however had limited impact on other air pollutants. Behavioural interventions showed limited effectiveness, with improvements not sustained over time. Higher AP generally increased concentration of IAPs, while outdoor pollutants such as PM2.5 and NO2 showed limited sensitivity to AP levels. CO2 concentration levels were found to be less reliable as an indicator of the overall air quality in residential buildings. A combination of technical and behavioural interventions should be considered to simultaneously improve IAQ and public health. Research limitations/implications: Longitudinal research across a wider range of housing types in different regions with different socio-economic backgrounds is required to provide a more comprehensive view on the correlations between IAQ, occupant behaviour, ventilation rates/strategies and physical characteristics of buildings, establishing more generalisable thresholds on IAQ and effective interventions to improve the conditions in social housing. Practical implications: The findings emphasise the need for integrated IAQ strategies in the context of retrofit and social housing, combining ventilation, air filtration and occupant engagement. Housing providers should prioritise ventilation strategies while retrofit programmes should mandate effective natural/mechanical ventilation whenever significant airtightness improvements are planned. Improving occupant awareness and behaviour along with development of technological interventions, such as smart ventilation systems and VOC-targeted monitoring and controlling technologies, are essential to improve public health. The findings suggest that poor IAQ may poses much higher risk to health than outdoor air. The governmental policies should therefore shift attention towards IAQ by developing practical guidelines on ventilation rates and limiting harmful indoor air pollutants from household materials as well as on the effects of retrofit and their implications on IAQ and health. Originality/value: This research provides a comprehensive real-world assessment of IAQ in social housing by integrating empirical monitoring, behavioural analysis and simulation modelling within a unified framework. It contributes to the understanding of how socio-technical interactions between occupants and building systems influence IAQ and offers actionable insights for improving health outcomes in vulnerable residential environments.