Deep energy renovations’ impact on indoor air quality and thermal comfort of residential dwellings in Ireland – ARDEN project

As Europe's residential energy renovation programmes accelerate, field studies assessing their impact on indoor environmental quality are required to ensure maximum co-benefits to occupants' health and wellbeing. In this work, we evaluated the impact of deep energy renovation (DER) on indoor air quality (IAQ), ventilation, and thermal comfort in a sample of Irish homes (n = 12). Indoor air pollutants (IAPs), including particulate matter (PM2.5), carbon dioxide (CO2), carbon monoxide (CO), formaldehyde, radon, nitrogen dioxide (NO2), and BTEX, were measured pre and post DER. Performance of the newly installed mechanical ventilation systems was also assessed. Questionnaires and diaries were used to collect feedback regarding the retrofit and occupant activities. All occupants reported high levels of satisfaction with thermal comfort, and homes were significantly warmer post-retrofit (p < 0.0001). The DER improved indoor CO2 concentrations, indicating a positive impact on residential ventilation. However, many bedrooms were still under ventilated. PM2.5 (p < 0.0001) and formaldehyde (p < 0.05) concentrations increased post-retrofit. Higher concentrations of PM2.5 were most likely due to a combination of factors including inadequate ventilation, ingress from outdoors via open windows or doors, presence of a wood burning stove and other occupant activities. Retrofits were observed to have poor compliance with ventilation recommendations. Greater emphasis on pollutant source control along with proper installation and maintenance of mechanical ventilation systems is required to ensure DERs lead to sustainable and healthy homes.