Gathering baseline data to assess household energy interventions' impact on indoor air quality, occupant health, and wellbeing: In2Air a non-randomized experiment.

BACKGROUND: Tackling climate change, together with improving indoor air quality, offers a significant opportunity to improve residents' health and well-being. This requires the evidence base to inform an energy-efficient retrofit design.

OBJECTIVES: (i) To develop a protocol that could be implemented by local authorities across a range of housing typologies and (ii) to deploy this protocol to establish baseline conditions in n = 30 homes ahead of energy-efficient retrofitting.

METHODS: Working with the local council and the community, this baseline study (In2Air) developed and deployed a protocol across 30 single-storey one- and two-bedroom properties owned by Newcastle City Council, United Kingdom, and occupied by tenants (> 55 years). The following data were collected before homes underwent a fabric-first intervention: indoor and outdoor air quality (for ~3 weeks); energy consumption (for ~12 months); occupant behaviour and home-specific details; self-reported general health and well-being.

RESULTS: The collected baseline data indicated that the mean PM2.5 (particulate matter < 2.5 µm in diameter) concentrations ranged from 3 to 24 µg/m3 (excluding three homes where smoking occurred indoors). No homes had monitoring period means above the current United Kingdom (2019) outdoor annual mean limit (25 µg/m3); however, 21 homes had monitoring period means above the current World Health Organization (2021) annual mean guidance value (5 µg/m3). Strong correlations were observed between indoor PM2.5 and indoor PM10 (particulate matter < 10 µm in diameter), suggesting similar sources, while no-to-weak correlations were observed between indoor carbon dioxide and indoor PM2.5. Moderate-to-good ventilation was suggested by indoor concentrations of carbon dioxide across all the study homes. The lack of correlation between carbon dioxide and particulate matter highlights the need for housing professionals to add particulate matter to their usual indoor air quality assessment suite of carbon dioxide, temperature and humidity. Most homes had mean humidity levels within the range considered healthy (i.e. between 40% and 60%), with only three homes above this range. With respect to the baseline health and well-being scores, compared to the comparison population, data for this initial time point indicated most participants (83%) had a physical health score below the norm, which likely reflects the age (> 55 years) of the cohort. In comparison, the mental health score for most participants (74%) was at or above average. Here, the physical layout of the estate with communal amenities may well be engendering a positive sense of belonging. The mean/median ICEpop CAPability score suggests a high level of capability across the cohort.

LIMITATIONS: Our study focused on changes to the building envelope across a limited number of building types and parameters and utilised fixed, low-cost sensors at indoor and outdoor monitoring locations rather than personal air quality monitors.

CONCLUSIONS AND FUTURE WORK: The baseline conditions reported in this article provide the basis on which to inform and evaluate the effects of energy-efficient refurbishment across this social housing stock as part of future research. The developed protocol and the study findings offer the potential to support and inform decision-making of council retrofit teams across the United Kingdom with their ongoing decarbonisation plans.

FUNDING: This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme as award number NIHR153617.