Analysis: Here's what Irish researchers learned about the impact of retrofitting on indoor air quality and how behaviour plays a role
By Asit Kumar Mishra, UCC; Victoria Hogan, Marie Coggins, Edel Doherty, Daniel Norton and Nina Wemken, University of Galway
In the European Union, low-income or social housing is often associated with poor indoor environmental quality (IEQ). This stems from factors such as the age of these residential buildings, poor maintenance, and a higher prevalence of indoor smoking. Poor indoor environments, often manifesting in terms of poor indoor air quality (IAQ), affect the habitability of the space along with residents' physical and mental health. For social housing, this impact can be even more important since the occupants in these homes are often more vulnerable due to their age and health status.
With the understanding that building energy retrofits can improve the indoor environment of homes, Irish residential retrofit programmes do focus on supporting low-income households through this transition. Last year in Ireland, more than half of the retrofit budget was dedicated towards such homes. The target is to retrofit at least 40,000 homes in these housing schemes by 2030.
It is important to understand the impact of energy retrofits, (e.g. replacement of fossil fuel-based heating systems with heat pumps and upgrades to the building envelope insulation) on the indoor environment of the homes. The Sustainable Energy Authority of Ireland sponsored the Health Impact Assessment of Energy Renovations on Irish Domestic Dwellings (HAVEN) research project, undertaken at the University of Galway, to understand the impacts of energy retrofits on indoor air quality and thermal comfort in a group of social houses, from 2020 through 2023. Over the past year, analysing the data gathered, the project has produced some positive and some interesting results.
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From RTÉ Radio 1's Today with Claire Byrne, A retrofitting Q&A with Ciaran Byrne and Brian McIntyre from the SEAI
After the energy retrofits, the building energy rating level rose in all homes to at least B2, making them more energy efficient than 70% of Irish homes. Along with this improved energy efficiency, most of the occupants felt that there was also an improvement in thermal comfort in the homes. People were more satisfied with the temperature indoors and the new heating systems. Part of the improved satisfaction was because they felt that typical sources of thermal discomfort, like draughts from windows, temperature changing a lot between rooms, and hot/cold surfaces on walls or windows had reduced. This is an expected result of the upgrades to windows and walls during the retrofit process. The improved thermal comfort achieved at a lower energy use is a definite win-win situation.
Post-retrofitting, the concentrations of fine particulate matter (PM2.5) and carbon dioxide (CO2) had increased in some homes. Such increases can occur if ventilation is not fully addressed as part of retrofit or building occupants do not engage fully with the new ventilation systems post-retrofit. Energy retrofit results in a more airtight building therefore the amount of outdoor air entering the homes for ventilation reduces. We observed that the few homes which did get a mechanical ventilation system as part of the retrofit were doing better in terms of indoor air quality.
Read more: What 70 Limerick home owners found out about air quality in their buildings
However, for some homes, the increase in indoor air pollutants was not mainly due to any aspect of the retrofit but due to occupant behaviour. Occupants were often not even aware of how they were adversely impacting the air they were breathing. For example, one of the main indoor air pollutants of concern for human health, PM2.5, is too small to be seen with our eyes and is odourless. We noted that occupant behaviours like blocking wall vents (used for ventilation), smoking indoors, and burning incense or candles indoors worsened the PM2.5 levels in homes, sometimes compounded by the poorer ventilation post-retrofit. The effect of such occupant actions dominated over the physical changes from retrofitting. Blocked wall vents were also associated with higher CO2 levels (which indicates poor ventilation) and greater likelihood of condensation and subsequent mould formation in the homes.
There were two related issues of concern here. One was that occupants often engaged in behaviour that compromised indoor air quality, and consequently could affect their health and wellbeing. Second was during the post-retrofit work handover, some occupants did not feel that they had received sufficient information on how best to use the ventilation systems and the heating systems (heat pumps) and what kind of maintenance work and at what frequency, were needed.
Read more: Do you know the indoor air quality of your retrofitted home?
A more thorough handover, with explanation of the technical aspects of the retrofit, including ventilation systems and heat pumps, is essential. Inadequate handovers can lead to energy-inefficient behaviours and dissatisfaction with the indoor environment and even lead to dissatisfaction with the retrofit process. The observations from this work also indicated that mechanical ventilation systems can become an integral part of all energy retrofits.
Effective communication to the public on the importance of ventilation and indoor air quality is also essential to optimise the benefits of energy retrofits for the indoor environment. Retrofit programmes should include tailored messaging for vulnerable groups, such as social housing tenants, to highlight the importance of ventilation, and raise awareness of sources of indoor pollutant, to improve indoor air quality literacy.
Overall, energy retrofits have the potential to create more sustainable and healthier dwellings. In addition to suitable design and selection of retrofit measures and smooth implementation, our findings indicate that increased engagement with occupants may prove to be a beneficial part of the process. Such engagement can improve the benefits from energy retrofits as well as encourage more people to be part of the home energy retrofit process.
The HAVEN study was funded by the Sustainable Energy Authority of Ireland under the SEAI Research, Development & Demonstration Funding Programme 2018, Grant number 19/RDD/435. Radon monitoring was funded by the Irish Environmental Protection Agency (EPA). The project team would like to thank the homes who participated in this study and the local authorities, approved housing bodies and retrofitting companies who supported the project.
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Dr Asit Kumar Mishra is a Research Fellow with the School of Public Health at University College Cork. Dr Victoria Hogan is a Lecturer in Occupational Health in the School of Health Sciences, University of Galway and is a researcher in the Health Promotion Research Centre. Dr Marie Coggins is a Senior Lecturer in Exposure Science at the School of Natural Sciences and a member of the Centre for One Health at the Ryan Institute, University of Galway. Dr Edel Doherty is an Associate Professor in Economics at the J.E. Cairnes School of Business and Economics, University of Galway. Dr Daniel Norton is a lecturer in economics at the J.E. Cairnes School of Business & Economics, University of Galway. Nina Wemken is a post-doctoral researcher in the School of Physics, School of Natural Sciences within the University of Galway. Her research focuses on human exposure to indoor air pollutants, with a emphasis on indoor air quality in retrofitted houses in Ireland.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
