Australian apartments built today may become unliveable by 2050, according to new research from the University of Sydney’s School of Architecture, Design and Planning.
The research warns apartments built to today's standards could become dangerously hot by 2050, prompting calls for urgent reform of Australia’s building codes.
Sydney apartments built to today's standards could become dangerously hot by the middle of the century, with residents in some areas facing weeks of indoor temperatures above safe comfort levels, the research warns.
The University of Sydney-led study is entitled Are code-compliant buildings ready for future climate : A case study of thermal autonomy in Australian apartments.
It applied future climate scenarios to apartments built to compy with Australia’s National Construction Code (NCC) and found residents susceptible to a dramatic increase in indoor overheating.
Lead researcher, Dr Shamila Haddad, said Australia is building homes for the future using standards designed for the climate of the past.
By the 2050s, median outdoor temperatures in Sydney's hotter inland areas could rise by up to 5°C under high-emissions climate scenarios, with hot days becoming longer and more frequent.
Under these conditions:
Apartments built to current standards could be too hot for comfort for the equivalent of around four weeks a year in Sydney and more than seven weeks a year in the western suburbs.
Indoor overheating risk increased consistently across all climate projections tested.
West-facing and top-floor apartments were particularly vulnerable because of low-angle afternoon sun and solar heat absorbed through roofs.
During extreme heat events, under the high-emission scenario, indoor temperatures could remain above 30°C for several consecutive days.
The findings have significant implications for public health, especially during prolonged heatwaves and potential power outages.
"In a future heatwave combined with a blackout, many apartments simply won't be able to keep residents safe," Haddad said.
Heat stress is an increasingly important issue for the health and well-being of populations exposed to high temperatures and humidity.
“While air conditioning can provide relief against heat stress, the widespread use of air conditioning can add pressure on electricity systems and even more heat to our cities,” Haddad said.
The research argues that Australia's building regulations should move beyond measuring energy efficiency based on historical weather data and instead assess a building's "passive survivability" - its ability to maintain safe indoor temperatures during extreme heat without relying on air conditioning.
Passive building strategies, including cool roofs, natural ventilation, and shading have proven to be effective in improving cooling comfort, while typically being affordable solutions.
The study found relatively straightforward design changes could dramatically reduce future overheating risks, including:
External window shading, which reduced overheating by up to 32 per cent;
Safe night-time ventilation, which reduced overheating by up to 34 per cent;
Lighter-coloured roofs to protect top-floor apartments; and
Insulation and double glazing.
In combination, these measures could reduce overheating risk by up to 94 per cent.
"If we're designing cities for 2050, we need to start designing buildings for the climate of 2050," Haddad said.
One organisation addressing the nation’s current housing stock challenge is the Australian Passivhaus Association (APA).
The organisation advocates for greater awareness of Passivhaus retrofit possibilities in improving existing housing stock.
Interestingly, retrofit projects in Australia have seen a 100% increase in the last three years.
Around 70 per cent of Australia’s 10.8 million homes were built before modern energy standards, with many performing at an average of just 1.8 NatHERS stars.
These homes are frequently uncomfortable, expensive to heat and cool, and increasingly prone to issues such as condensation and mould.
Conventional responses such as knock-down rebuild or upgrades to minimum code offer limited long-term value.
Rebuilding carries a high embodied carbon cost, while minimum compliance risks becoming rapidly outdated and does not guarantee performance in practice.
Evidence also suggests that poorly considered upgrades, particularly around airtightness without ventilation, can exacerbate indoor air quality issues.
The solution is the Passivhaus retrofit standard EnerPHit which involves specific upgrades to the building envelope, airtightness, ventilation, and thermal performance as a whole system.
This approach aims to close the gap between design and as-built outcomes while delivering consistent indoor comfort, low energy demand, and healthy air quality.
It also provides a framework for future-proofing buildings against tightening regulations and changing climate conditions.
With the average home built before 2010 and performing at just 1.8 out of 10 stars for energy efficiency, APA CEO, Stalin Chakrabarty, said the need for retrofits has never been more urgent.
“This isn't about knocking down what we've built. It's about proving that our existing housing stock can perform to a genuinely healthy, comfortable, and low-carbon standard,” he said.
“Australia cannot meet its climate and housing goals through new construction alone. We must also improve the buildings we already have.”
Bureau of Meteorology figures show Australian temperatures are increasing with the warmest year on record was in 2019, and eight of the nine warmest years on record have occurred since 2013.
The very high monthly maximum temperatures that were recorded under 2% of the time in 1960−1989, are occurring 11% of the time in 2009−2023. That is about six times as often.
Similarly, the very high night time temperatures, which are also a major contributor to heat stress, and occurred 2% of the time in 1960−1989, now occur about 10% of the time – five times as often.