Simple retrofits to ageing social housing could reduce residents' exposure to indoor temperatures associated with health risks in a changing climate, UNSW researchers have found.
For many people living in social housing, keeping a home at a safe temperature can mean difficult trade-offs.
Rising costs of rent, food and health care often need to be weighed against staying comfortable during extreme weather events like heatwaves and cold snaps. Researchers call this 'energy poverty': when people can't afford to keep their homes warm in winter or cool in summer because basics like food, housing and health care come first.
New research from UNSW published recently in the City and Environment Interactions journal suggests the problem is set to become worse as climate change increases exposure to extreme temperatures. It also suggests part of the solution may lie in the buildings themselves, where passive upgrades - like shading or window glazing - could improve thermal resilience in ageing high-rise social housing while reducing residents' exposure to extreme indoor temperatures.
A tale of two apartments
The study looked at two high-rise social housing buildings in Redfern and Surry Hills and found that overheating could become substantially more common under future climate conditions, particularly in west-facing apartments exposed to the afternoon sun, where annual hot hours increased by as much as 74%. The research also showed some apartments are far more vulnerable than others, depending on factors such as orientation and floor level.
"Thermal risk is not distributed evenly across a high-rise building. West-facing and upper-level apartments may experience substantially greater overheating, which means retrofit programs should prioritise the dwellings facing the greatest exposure," UNSW researcher Dr Gloria Pignatta says.
"This means the most effective retrofit strategy may depend on where an apartment is located within a building. Rather than applying the same upgrade everywhere, targeted interventions could deliver greater benefits and better value for money."
The research modelling revealed substantial evidence of energy poverty in the case-study buildings. Achieving thermal comfort in July would have required 17-20 hours of full power heating per day, equivalent to around 848-978 kWh per dwelling. But during this time, residents used portable heaters for only two to three hours per night.
"The modelling suggests that overheating will become much more common by 2050, with hot hours rising from around 100 hours under current climate conditions to almost 175 hours under a future climate scenario. For residents already facing financial pressure, these conditions could have serious implications for health, well being and quality of life," Dr Pignatta says.
While energy poverty is often understood as an affordability issue, the researchers argue that housing quality is also part of the equation.
Building resilience
The buildings examined in the study had no air conditioning and relied on natural ventilation for temperature regulation. Being of older construction with limited insulation and a design that did little to account for the daily and seasonal movement of the sun, the buildings absorbed heat during summer and lost it during winter, increasing the exposure of residents to extreme indoor temperatures.
The researchers approached the project with a question about how to tackle the knock-on effects that energy poverty brings to residents' lives: which upgrades would make the biggest difference with limited budgets available?
To answer that question, the researchers used computer modelling to test a range of 'passive' retrofit strategies - building upgrades designed to improve thermal comfort without requiring ongoing energy use. These included external shading devices, insulation upgrades, double glazing, increased natural ventilation, and reflective façade coatings. The researchers also considered the influence of existing tree shading on indoor thermal conditions, particularly in lower-level units, which is the subject of an upcoming study.
Designed for comfort
The results suggest relatively simple changes could substantially improve indoor thermal conditions.
The modelling found shading delivered the strongest reduction in overheating, reducing the number of hours above 30°C by up to 50% under future climate conditions.
Meanwhile, insulation upgrades reduced exposure to cold conditions by around 25%, while double glazing delivered benefits across both summer and winter.
"Our findings show that improving thermal comfort doesn't always require major redevelopment or expensive new technologies," says Dr Pignatta.
"Relatively simple upgrades such as shading, insulation and double glazing can significantly reduce residents' exposure to extreme indoor temperatures. That's particularly important for social housing residents, who are often among the most vulnerable to the impacts of extreme heat and cold."
The next question was not only which retrofit performs best thermally, but which option is most appropriate when cost, construction disruption, embodied carbon and resident impacts are also considered.
"Overall, our research shows that there is no single best retrofit for every building or every decision-maker," Dr Pignatta says.
"Overhang shading combined with mineral wool provided the strongest thermal performance, while reflective paint combined with mineral wool offered a more favourable balance of cost, feasibility and environmental impact. The appropriate choice depends on the priorities of residents, housing providers and governments.
"The purpose of this research program is to connect detailed building-performance analysis with the decisions that housing providers and governments actually have to make. A retrofit may perform well thermally but still be difficult to install, expensive to deliver or carbon-intensive. These trade-offs need to be considered together."
Why passive solutions work
Unlike air conditioning or heating systems, passive retrofits can reduce exposure to extreme indoor temperatures with little or no ongoing operational energy use. This is particularly important for households experiencing energy poverty, where the cost of maintaining safe indoor temperatures can place pressure on already stretched household budgets.
"We already know that severe heatwaves claim more lives than any other natural hazard in Australia," Dr Pignatta says.
"Spending long periods in homes that are too hot in summer or too cold in winter can have serious impacts on health and well being, particularly for people living in vulnerable circumstances."
The researchers hope the findings will help housing providers and governments prioritise future upgrades to social housing. Dr Pignatta says the study provides a practical framework that councils, housing providers and developers can use to prioritise retrofit investments in ageing apartment buildings.
"Under climate change, energy poverty is not only about whether residents can afford heating and cooling. It is also about whether the buildings themselves protect residents from extreme indoor temperatures and therefore a housing-quality and climate-resilience issue.
"This issue may be addressed through relatively simple, affordable and practical building upgrades, without forgetting that retrofit decisions need to consider thermal performance alongside cost, construction feasibility, embodied carbon and the priorities of residents," she concluded.
