Simple upgrades to ageing social housing could reduce residents’ exposure to indoor temperatures linked to health risks as the climate changes, according to new UNSW research.
For many social housing residents, staying comfortable during heatwaves and cold snaps means difficult trade-offs against rising costs of rent, food and health care.
The study, published in City and Environment Interactions, examined two high-rise social housing buildings in Redfern and Surry Hills.
It found overheating could become substantially more common under future climate conditions, particularly in west-facing apartments exposed to the afternoon sun, where annual hot hours rose by as much as 74 per cent.
Orientation and floor level made some apartments far more vulnerable than others.
Modelling suggested hot hours would climb from around 100 under current conditions to almost 175 by 2050, with implications for residents’ health and wellbeing.
The research also found substantial evidence of energy poverty, which occurs when people cannot afford to keep their homes warm in winter or cool in summer because basics come first.
Achieving thermal comfort in July would have required 17 to 20 hours of full-power heating per day, equivalent to around 848 to 978 kWh per dwelling.
Residents, however, used portable heaters for only two to three hours a night.
The buildings had no air conditioning and relied on natural ventilation.
Their older construction, limited insulation and a design that did little to account for the sun’s movement meant they absorbed heat in summer and lost it in winter.
Researchers used computer modelling to test passive retrofit strategies, which are building upgrades that improve thermal comfort without requiring ongoing energy use.
These included external shading, insulation upgrades, double glazing, increased natural ventilation and reflective façade coatings.
Shading delivered the strongest reduction in overheating, cutting hours above 30 degrees Celsius by up to 50 per cent under future climate conditions.
Insulation upgrades reduced exposure to cold by around 25 per cent, while double glazing delivered benefits in both summer and winter.
UNSW researcher Dr Gloria Pignatta said the results showed major spending was not always necessary.
“Our findings show that improving thermal comfort doesn’t always require major redevelopment or expensive new technologies,” she said.
The team also weighed cost, construction disruption, embodied carbon and resident impacts.
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.
Dr Pignatta said there was no single best retrofit for every building, and that targeted interventions, rather than the same upgrade everywhere, could deliver better value for money.
Unlike air conditioning or heating, passive retrofits can cut exposure to extreme temperatures with little or no ongoing energy use, an important advantage for households with stretched budgets.
“We already know that severe heatwaves claim more lives than any other natural hazard in Australia,” said Dr Pignatta.
The researchers hope the findings will help councils, housing providers and developers prioritise retrofit investments in ageing apartment buildings.
A follow-up study will examine how existing tree shading affects indoor conditions, particularly in lower-level units.