Sydney is no stranger to extreme heat. In January 2020, Penrith in Western Sydney reached 48.9°C, the highest temperature ever recorded in Greater Sydney.

Now imagine Penrith in 2050: the heat lasts longer, extreme heat events happen more often, and power goes out on the hottest days because the grid can’t cope.

Our recent research, published in the journal Energy and Buildings, shows Sydney apartments built to current building codes may become very uncomfortable by 2050 far more often. In fact, we found that inside an apartment built to today’s standards, temperatures would stay above 30°C for several days in a row.

Sydney is rapidly rezoning, leads the nation in apartment living, and is still racing to build more homes. Many of the developments approved today will still be standing in 2050.

But while we are building for the future, we are designing for the past.

Building for yesterday’s climate

Our study used the latest climate projections for Sydney to test apartments built to today’s standards in inner-city Redfern and Western Sydney’s Penrith.

By the 2050s, owing to climate change, Sydney’s median outdoor temperatures could be up to 5°C higher than today in its hotter inland areas under the highest-warming regional projection (a high greenhouse gas emissions scenario known to researchers and policymakers as SSP3–7.0), with hot days becoming longer and more frequent.

We found apartments built to today’s standards could be too hot for comfort for the equivalent of about four weeks a year in Redfern and more than seven weeks in Penrith.

Design matters. West-facing homes receive intense afternoon sun, while top-floor apartments absorb heat radiating through the roof. Opening a window offers relief when the air outside is cooler. But many apartments lack cross-ventilation, and others have windows too small to remove the heat that builds up indoors.

A threat faced unequally

Older people, poorer communities, and people with chronic illnesses face the greatest risks.

Our projections show people living in Penrith could face almost twice as much overheating inside their homes as people in Redfern.

Air conditioning (AC) isn’t always an option. This is especially true for renters, elderly residents, and low-income households who make up much of western Sydney’s growing apartment population.

Some renters may not be allowed to install AC. And even where it’s already installed (it is not mandatory in new builds), not everyone can afford to run it.

One national longitudinal study estimated about one in 14 Australian households (around 7% of households) already spends more than 10% of their income on energy bills.

A survey of more than 1,000 Australians found 49.7% of households resist using their AC units on hot days to save on summer electricity bills.

Running air conditioners during extreme heat also puts enormous strain on the electricity grid. On hot summer days, NSW peak electricity demand can surge above 13,000 megawatts, well above the state’s average operational demand of around 7,700 megawatts, straining the grid and increasing the risk of blackouts.

During a blackout, even homes with AC may lose cooling when they need it the most. Air conditioners also release heat outdoors, making already hot neighbourhoods even hotter.

To sum up: many people cannot rely on AC and may not be able to easily relocate during a heatwave.

Homes should be able to keep people safe even when AC is not available.

Two changes could make a major difference

The solution starts with building standards. Australia’s current construction code focuses on predicted energy use for heating and cooling based on historical weather data, not the warmer climate those buildings will face. They should also test how long a home can stay at safe temperatures in a warmer future, especially during heatwaves, without relying on AC. This is known as a building’s “passive survivability”.

To make homes safer, we need two changes to building standards.

First, new apartments should be tested against a range of future climates, including longer and more intense periods of heat.

Second, standards should set a minimum time that a home must stay safe without air conditioning and provide practical guidance on how to achieve this.

Better design can cut the risk

Adding more insulation on its own doesn’t go far enough to protect apartments from future heat. But our study found several design changes that can make a real difference:

External window shades block sunlight before it heats the apartment. We found they reduced the time apartments were too warm by up to 32%
Safe night-time ventilation – meaning windows you can leave open overnight – lets trapped heat escape after sunset. We found it reduced overly warm hours by up to 34%, especially in Penrith
Lighter roof colours also helped protect top-floor apartments.

The best results came from combining these measures with double-glazed windows and insulation. Together, they cut the risk of Sydney apartments becoming too hot in the 2050s by up to 94%.

Australia needs more apartments. But homes approved today must still protect people decades from now.

Building codes need to change so the country’s growing apartment stock stays safe, liveable and resilient in a hotter future.

More broadly, planning for new developments should also combine urban-scale heat mitigation measures (such as urban greening, light-coloured or reflective materials for roofs, roads and pavements, providing shade for built surfaces, and designing with water) with building adaptation to offset the impacts of climate change.

Our study focused on Sydney, but it is likely these findings are applicable across many other parts of Australia and the region.

By Shamila Haddad, University of Sydney; Arianna Brambilla, University of Sydney; Jingjing Liu, University of Sydney, and Mat Santamouris, UNSW Sydney.

Image: Envato.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Architecture & Design Team

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