Pathways to Climate Adapted and Healthy Low Income Housing
Adaptation Research Grants Program
Executive summary from final report:
This report presents the findings from the “Pathways to Climate Adapted and Healthy Low Income Housing” project undertaken by the CSIRO Climate Adaptation Flagship in partnership with two organisations responsible for providing social housing in Australia.
The project was based on the premise that interactions between people, housing, and neighbourhood are dynamic and best viewed as a complex, dynamic social-ecological system. Using social housing as a case study, the objectives of the project were to:
- Model the vulnerability of housing and tenants to selected climate change impacts;
- Identify/evaluate engineering, behavioural and institutional adaptation pathways;
- Scope the co-benefits of climate adaptation for human health and well-being; and
- Develop house typologies and climate analogues to enable national generalisation.
This project was developed with the rationale that a multi-level focus on the cross-scale interactions between housing, residents, neighbourhood, and regional climate was vital for understanding the nature of climate change vulnerability and options for adaptation.
The climate change hazards that were explored were increasing temperatures and more frequent and severe heatwaves in the context of heat-related health risks to housing occupants, and changes in radiation, humidity, and wind, in relation to material durability and service life of housing components and the implications for maintenance.
Neighbourhood and role of place
Heat vulnerability mapping was undertaken to identify spatial relationships between thermal patterns of land surface temperature and the risk factors that define sensitive populations. This analysis was conducted in four Australian cities, including Adelaide, Melbourne, Sydney and Brisbane. These cities were selected as they were the most documented in terms of research on the links between extreme heat and public health.
Low income households were defined as those with an Equivalised Total Household Income in 2006 of between $1 and $399 per week. Key risk factors for heat-related health were often twice as prevalent in low income households compared to those on medium to high incomes. Significantly, many of the risk factors were also found to coincide, for example, elderly people who are living alone and also need assistance.
Significant variations were seen in patterns of land surface temperature for each of the four cities investigated. Low income households were typically associated with parts of the city with the highest land surface temperatures. As such, those most vulnerable to heat-related health impacts were often living in areas with the highest heat exposure, as measured by land surface temperature. This pattern was consistent for all four cities investigated. Generally, cooler parts of the city had higher vegetation cover.
Thermal performance of housing
Modelling of the thermal performance and indoor environment of low income housing was undertaken using the AccuRate software for residential house energy rating. A key first step was the construction of a housing typology, based on the social housing dataset provided by project partners. Comprising 142,410 housing assets, this dataset represented around 35% of the households being assisted by social housing nationally and covered all major climate zones as defined within the Building Code of Australia.
Ten common house types were identified, characterising the broad range of house designs, construction processes, and materials used in low income housing. Thermal performance and indoor environment of each house type, in each climate zone, was assessed using a widely recognised measure of heat-related health risk known as the Discomfort Index (DI), implemented as a module in the AccuRate software. Future climates in 2030, 2050 and 2070 were generated using the MIROC-M Global Climate Model and A1FI emission scenario. House types in climate zones with hot and humid summers were found to be most vulnerable. In these locations, house retrofits cannot mitigate the level of severe heat-related health risk (DI > 28) and air-conditioning will be increasingly required to maintain a safe indoor thermal environment. Retrofits are more effective in temperate locations, largely ameliorating climate impacts in the short term. Overall, it was estimated the energy required for cooling a typical slab-on-ground, brick veneer home could grow by 75-115% in Melbourne and 95-359% in Brisbane, by 2070.
While some house types perform better than others, most of the variation in thermal performance was due to quality rather than type of housing. If building orientation is good, than in most situations a simple building retrofit could greatly improve thermal performance. For example, using weather data from the January 2009 heatwave in Melbourne, simulations using AccuRate have shown that on average across the house types, a ‘cheap retrofit’ could reduce severe heat-related health risk (DI > 28) by 25%.
Material durability and service life
The durability of materials commonly used in housing construction was assessed for the impacts of climate change. The degradation processes considered, included the atmospheric corrosion of metal (both steel and zinc) and the fungal decay of timber used in above-ground and in-ground applications. Modelling was undertaken using climate projections from nine Global Climate Models with the A1FI emission scenario.
The analysis has revealed that on average, by 2100 in Melbourne, the rates of steel and zinc corrosion could decrease by 14% and 9% respectively, whereas in Brisbane the corrosion rates for the same metals could increase by 14%. Changes in rates of timber decay were similar, with Melbourne to experience an average decrease of 17% and 11% by 2100 for above-ground and in-ground applications, respectively. Little change was predicted in the average rate of above-ground timber decay in Brisbane over this timeframe, but in-ground timber decay could increase by an average of 14%. These results were used to estimate the change in service life of housing components made from these materials. The impact on housing maintenance costs was estimated to be small (~5%), but this may be significant for a large housing portfolio manager.
Evaluation of adaptation pathways
Information was collated on exposure, sensitivity and adaptive capacity at both building and neighbourhood scale. This was used to assess the vulnerability of 103,809 social housing assets for which full data was available. Approximately 5% were considered to be highly vulnerable, with high potential impact from climate change and low adaptive capacity. These were typically located in climate zones with hot and humid summers and will be increasingly reliant on air-conditioning. A further 4% also had high potential impact, but with high adaptive capacity, meaning there is scope to reduce heat-related health risk through adaptation. This includes urban greening to control land surface temperatures in the outdoor environment; upgrade of assets through changes to roof colour and installing ceiling insulation to reduce indoor temperature extremes; as well as various behavioural and institutional adaptation actions to maximise effectiveness.
Conclusions and next steps
This project has confirmed that the housing and neighbourhoods in which low income households live can exacerbate heat-related health risk. In most cases, there were a range of options available to help mitigate this risk. Next steps are to further distil the findings into guidelines for climate adaptation in low income housing. Given the social housing focus in this project, a necessary prerequisite is to determine how the findings translate to other low income housing types and how capacity to respond might vary.