“Increasing but also changing”: Wetter and hotter weather patterns increasing mould risk

With extreme rainfall events, flooding and humidity on the rise, the prevalence of mould in Melbourne’s eastern suburbs has kept up with the national average – and with weather patterns only looking to make things warmer, that is not expected to change. 

🗣️ University of Melbourne School of Population and Global Health Professor, Rebecca Bentley, said between 25 and 30 percent of houses in Melbourne’s eastern suburbs are likely home to mould growth.

More moisture, more mould: Mould is a microscopic fungus that can grow on surfaces prone to being damp, or in rooms or environments of high levels of humidity, condensation or water vapour.

Increasingly, Australia’s climate has been developing into one that’s a perfect habitat for mould.

Warmer Earth, more moisture: According to the State Government’s 2024 Climate Science Report, with each degree the Earth warms, the atmosphere can hold about seven percent more water vapour, leading to more moisture in the air and more extreme weather patterns.

Environment Victoria reports global warming – and humanity’s dependence on fossil fuels – directly causes this extra water to be created and stored.

Modifying moisture: Professor Bentley said changing weather patterns, shifts in humidity and more storms and floods carried the risk of worsening Melbourne’s mould problems.

“It is likely that the problems that we're having in our houses with mould will be increasing but also changing,” she told the Eastern Melburnian.

"Places that weren't previously experiencing a lot of problems with humidity might now be.

“They might not have housing built in a way that can deal with that.”

Health impacts: Household mould can cause or worsen a number of physical health problems, including asthma and infections.

A 2018 study estimated that 7.9 percent of asthma in Australian children was caused by indoor dampness.

Hidden stress: Professor Bentley said on top of the many physical risks of living with mould, the impacts on mental health were “under acknowledged” 

"Just knowing that the mould is there, not knowing necessarily what to do about it or being uncertain about how it might impact their health, does create a lot of anxiety for people,” she said.

Financial hurt: In 2023, Professor Bentley told the ABC the financial impact of mould in Australia could reach $1.35 billion in healthcare expenditure and $7.5 billion in productivity losses.

In a report Bentley co-wrote in 2024, projections found that if indoor mould could be eliminated completely in Australia, the country’s health expenditure would decrease by $2.82 billion and income would increase by $4.21 billion over the next 20 years as it would mean Australians would live for a cumulative 109,000 more years.

Building for a changing environment: While there have been some changes in building regulations aimed at preventing mould, Bentley said more proactive action is needed.

"The quality of housing stock and the match for climate are really important drivers in the reason why we have mould in our homes,” she said.

"It's not a straightforward proposition that the older the home is, the more likely it is to get mould.

“It's more about the design of the home, the orientation, how it's been maintained.”

In 2005, changes to the National Construction Code meant new builds had to be more energy efficient, holding heat in winter and becoming insulated from it in summer.

Architectural scientist Dr Tim Law, who specialises in mould in Australian buildings, told the North Shore Lorikeet in August he believed the country’s mould problems began to intensify around this time, as the changes didn’t factor in a rise in condensation - one of the key triggers for mould - and how that could be managed.