Energy efficiency retrofits are central to climate policy, yet their implications for indoor environmental quality (IEQ) and occupant health remain underexplored. This study investigates IEQ outcomes following staged retrofits in Irish social housing, where achieving Building Energy Rating (BER) targets is the primary performance metric. Four dwellings, three retrofitted and one control, were monitored over six weeks during the heating season. Built in the 1980s, these homes represent the typical social and private housing stock of that era. Continuous measurements of carbon dioxide, temperature, relative humidity, and thermal performance were complemented by analyses of vapour pressure excess and ventilation rates. While all retrofitted homes achieved BER improvement targets, persistent IEQ challenges were identified. Elevated pollutant concentrations and increased condensation/mould risk occurred in the presence of inadequate ventilation. Thermal anomalies and cold bridging were associated with cavity wall insulation, whereas external wall insulation provided more stable surface temperatures and reduced moisture-related risks. These results underscore the complex interplay between retrofit measures, occupancy patterns, and ventilation performance. The study highlights the need for retrofit strategies that integrate energy efficiency with occupant health objectives. At scale, retrofit programmes risk embedding systemic vulnerabilities unless ventilation and moisture control are prioritised, with implications that extend to health, wellbeing, and long-term building resilience.

Energy efficiency retrofits are central to climate policy, yet their implications for indoor environmental quality (IEQ) and occupant health remain underexplored. This study investigates IEQ outcomes following staged retrofits in Irish social housing, where achieving Building Energy Rating (BER) targets is the primary performance metric. Four dwellings, three retrofitted and one control, were monitored over six weeks during the heating sea-son. Built in the 1980s, these homes represent the typical social and private housing stock of that era. Continuous measurements of carbon dioxide, temperature, relative humidity, and thermal performance were complemented by analyses of vapour pressure excess and ventilation rates. While all retrofitted homes achieved BER improvement targets, persistent IEQ challenges were identified. Elevated pollutant concentrations and increased condensation/mould risk occurred in the presence of inadequate ventilation. Thermal anomalies and cold bridging were associated with cavity wall insulation, whereas external wall insulation provided more stable surface temperatures and reduced moisture-related risks. These results underscore the complex interplay between retrofit measures, occupancy patterns, and ventilation performance. The study highlights the need for retrofit strategies that integrate energy efficiency with occupant health objectives. At scale, retrofit pro-grammes risk embedding systemic vulnerabilities unless ventilation and moisture control are prioritised, with implications that extend to health, wellbeing, and long-term building resilience.

To date, much of the research on overheating risk in dwellings has been focused on warmer climates, there is however increasing ­concern regarding overheating risk in dwellings including in cool climates, exacerbated by both large scales retrofit and the potential impacts of climate change. Dwelling overheating has been linked to impacts on sleep, health and wellbeing, including increased rates of mortality and morbidity. This paper explores overheating risk in dwellings in cool climates using Ireland as use case. Ten representative vernacular Irish dwellings were identified and monitored over the summer months of 2024 (June-August inclusive). To understand the role and impact of occupant behaviours, quantitative sensor data was coupled with occupant surveys. The research demonstrates that risk of overheating is found in cool climates, a risk that is likely to be exacerbated by a warming climate. High thermal specification dwellings such as deeply retrofitted and newer dwellings present the greatest risk of overheating. Indeed, thermal specification may be a key contributory factor over typology alone. The identified risk is generalisable to other jurisdictions with cool climates, particularly where, like Ireland, national retrofit strategies are underway. Large scale monitoring, surveys and dynamic simulation modelling are required to confirm the key contributors to overheating risk in dwellings in cool climates and to develop resultant protections. Feedback from occupants demonstrates a varied application of user adaptations. In addition to design-led mitigation measures, occupant education on appropriate adaptation measures is recommended.