Why are Sydney homes so mouldy? One expert unpacks the fungal facts

According to architectural scientist Dr Tim Law, Australia has created “an entire generation of building stock” without the capacity to manage mould and condensation.

And, as Law pointed out to the Lorikeet, it needn’t have been this way, given North America and Europe began addressing the problem in the 1970s.

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.

Law suggested Australia’s mould problem began to intensify at 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.

So what can we do now? 

While amendments were made to the National Construction Code in 2019 and 2022 to consider condensation management, including the use of air conditioning, Law regarded these as “baby steps”. 

In the war against mould, Law said we were on the backfoot due to materials used in construction, in particular cellulose-based materials such as softwood.

“If we use cellulose as a large part of our construction, we are actually creating an abundant nutrient base: things like Radiata Pine, a fast-growth softwood, [is] very susceptible to mould attack.”

The phases of the mould

Law explained that mould has two phases: germination and growth.

“Think about it as growing a lawn,” he said. “After you lay the seeds for the lawn, you have to water it daily. Once the grass is established, it can grow on its own, and only the occasional rain can keep it growing.”

The best chance to break mould’s lifecycle is in the germination phase — before it is visible to the human eye — by preventing an atmosphere of continuous high humidity.

If we can’t eliminate the nutrient source, the best recourse is through devices like dehumidifiers. Law recommended regularly dehumidifying rooms, even if mould is not readily apparent. 

“You want to keep the air well below 60 percent humidity.”

Image credit: Nancy Hughes via Unsplash