The Impact of Deep Energy Renovations on Indoor Air Quality and Ventilation in Irish Dwellings

Achieving energy-efficient dwellings has become a vital part of the global climate action plan to reduce energy usage and carbon emissions. Deep energy retrofits (DER) can help reduce residential energy use significantly. However, evidence on how DER impacts on indoor air quality (IAQ), and consequently, occupant health, is scarce. More in-depth analysis of IAQ data before and after energy retrofits is essential to understand the indoor environmental challenges of adopting energy efficiency measures. DER will be required to achieve the EU target of zero emission building stock by 2050, and such studies can inform policy as retrofit strategies evolve. This study evaluates the IAQ in a sample of domestic dwellings (n=12) in Ireland before and after undergoing DER, as part of the SEAI funded research project (ARDEN). IAQ pollutants, including PM2.5, carbon dioxide (CO2), carbon monoxide (CO), formaldehyde, radon, nitrogen dioxide (NO2), and BTEX (Benzene, toluene, ethylbenzene, and xylenes) were measured over a period of 48 hours to three months (depending on the pollutant) using continuous and passive sampling methods. This study further assesses the performance of the mechanical ventilation systems installed in the homes post DER. The results show that higher concentrations of PM2.5 were recorded in some homes post-retrofit compared to pre-retrofit. This was likely due to a combination of factors – increased air tightness (i.e., reduced infiltration), the new mechanical ventilation systems not achieving design flow rates, and varied occupant activities during measurement period. Overall, formaldehyde concentrations significantly increased (p <0.001) post-retrofit, most likely due to the use of building materials, paints, and furnishings during retrofitting. Radon levels measured post-retrofit were below the Irish national reference level (i.e., <200 Bq m-3) for most homes sampled (n=26), except for four homes which were in high radon areas. Results suggest that more emphasis is needed on improving the design, installation, commissioning and maintenance of ventilation systems, along with raising homeowner’s awareness regarding IAQ, and how to operate and maintain their ventilation systems in an efficient and effective manner. This would support good IAQ in the energy efficient homes, ensuring health and wellbeing.