Five ways to prevent mould in your home and the best ways to clean it

Winter is here, and with it comes the increased risk of mould in homes, particularly in colder parts of the country.

And although often dismissed as an issue to be dealt with later, mould can quickly get out of hand and can also pose a health risk.

To prevent mould growing in your home, it helps to understand what it is and what it needs to survive.

"Mould is always already there ... it floats around in the air, and every surface contains a couple of spores," Neumeister-Kemp says.

When it comes to household mould, common types are often referred to by their colour, such as brown, green, and black mould.

But Jason Chapple, a Brisbane/Meanjin-based master water damage technician and co-founder of The Mould Group, says the colour of mould can't tell you how harmful or what species it is.

"We can't identify what sort of mould it is [with certainty] … without a lab."

Perth/Boorloo mycologist Heike Neumeister-Kemp explains that mould, which includes many different species, is a type of fungi that feeds on organic matter and reproduces by releasing tiny spores.

Stachybotrys chartarum, sometimes called black mould, has a reputation as particularly toxic to humans. However, other mould species can also release mycotoxins that cause serious harm.

The good news is that the basic prevention strategies are the same for every species.

NSJ Envirosciences principal mycologist David Lark, from Newcastle/ Mulubinba, says mould spores need water, food, oxygen and the right temperature to reproduce.

"Then the square is complete, and it grows," he says.

When and how mould becomes an issue differ depending on the climate where you live, but all three experts say preventing it is fundamentally about limiting potential food and water sources.

Here are five ways they recommend doing it.

1. Keep home surfaces clean

To grow, mould needs organic matter to feed on, and skin cells, dirt and bacteria will do the job.

"We say microscopic food source because a handprint is good enough," Chapple says.

For this reason, the experts say regular home surface cleaning is essential.

In addition to weekly floor, benchtop, and bathroom cleaning, Chapple says all walls, ceilings, and windows should be wiped down every 12 months.

"You only need to use washing-up detergent [well-diluted in water]," Chapple says.

"Since mould is a winter issue [in many places], that's when you should clean it — before it actually becomes an issue."

Once you've cleaned, Neumeister-Kemp says there are also commercial products containing plant saps that will protect surfaces that are prone to mould, for example, in bathrooms.

"The product needs to be non-toxic [and] it should be TGA approved," she says.

2. Measure and control humidity

Put simply, relative humidity is the amount of water vapour in the air.

There are several ways to measure it, but one of the cheapest is a basic hygrometer ($10–20).

Once you've got something to measure the relative humidity in your home with, Lark recommends keeping it below 60 per cent to prevent mould.

Ways to control humidity include:

Ventilating your house by opening windows and doors on dry days (when the humidity outside is lower).

Using a dehumidifier in rooms with lots of moisture, and during damp seasons for your climate zone.

While Neumeister-Kemp questions the value of domestic dehumidifiers, Chapple and Lark believe they can be effective.

Chapple says tracking the relative humidity in parts of your home and moving your dehumidifier as required can work.

But he says larger spaces with higher water volumes may require more than one dehumidifier.

Lark says running your air con on dry mode, if it has one, is another option for reducing moisture in the air.

3. Tackle condensation

Window and wall condensation can become a major problem in winter, particularly in colder parts of the country where indoor heating is necessary.

What happens is when the warm air hits the cold windows … moisture appears on the inside," Chapple says.

And the issue is often the worst in bedrooms.

"While we're sleeping, per person that's in that room, we're adding … moisture to the air [when we breathe]," Chapple says.

To avoid mould caused by condensation:

Neumeister-Kemp says sleeping with your door open can help increase the air volume and keep the humidity lower.

All three experts recommend drying morning condensation on windows and walls, and the simplest method is wiping the area with a clean, dry cloth daily.

Lark and Neumeister-Kemp both recommend slightly warming cold rooms so that surfaces stay warm enough to prevent condensation.

4. Don't add moisture to the air

Some everyday activities can inadvertently "dump litres of water vapour" into the air inside your home, Lark says.

But there are some easy ways to avoid raising the relative humidity:

Always run your kitchen rangehood during and after cooking, Lark says.

All three experts also recommend running your bathroom exhaust fan during and after showers.

Neumeister-Kemp says the fan should be run for at least 10 minutes after showering, while Chapple recommends 20–30 minutes.

When buying a new clothes dryer, experts recommend choosing one that collects moisture from wet clothes rather than pumping it into the air. Mr Lark recommends condenser dryers, and Chapple suggests heat pump dryers.

And both men also warn against using unflued gas heaters, which pump moisture into the air.

5. Address water leaks and spills quickly

Lark says mould can establish within 24–48 hours on wet surfaces, fabric and carpet.

Addressing water leaks in your home quickly is important, as is drying spills, so don't put it off until next weekend, he says.

How to clean mould that's just appeared

Cleaning any mould can throw harmful spores into the air.

Lark says that a professional should also deal with mould in the homes of people with respiratory issues.

For those who don't fall into these categories, new, small patches of mould can be cleaned, but protective gear should be worn, including gloves, eyewear, and a P2/N95 face mask, Lark says.

Neumeister-Kemp recommends wiping the area with a cloth soaked in a solution of 80 per cent vinegar and 20 per cent water.

"That is good to clean, but not to prevent," she warns.

Washing-up detergent and water, in the ratio used for doing the dishes, is the solution Chapple and Lark suggest.

But the physical act of wiping away the mould is key, as dead mould can still be toxic.

"The goal is to remove it, not merely kill it in place," Lark says.

However, he warns that if underlying water issues are not addressed, cleaning will only be a short-term fix.

Does clove oil work as a cleaner?

Clove oil — usually a quarter of a teaspoon in a litre of water — is often touted as the best way to clean mould, but Neumeister-Kemp and Chapple say they don't recommend it because it leaves an oily film.

Lark explains that while clove oil as a mould cleaner is not "snake oil", it is oversold.

The active component, eugenol, damages the fungal cell membrane and inhibits spore germination, he says.

But Lark says there is "very little peer-reviewed work" on clove oil's value as a mould-cleaning agent in buildings, and most current research is focused on food preservation, protecting harvested crops, and food-packaging films.

He says the eugenol in clove oil "isn't doing nothing" and can suppress mould regrowth when used as a cleaner, but its protective effect fades as it evaporates.

"And any oily film — clove oil or otherwise — collects airborne dust and skin cells, and it's that soil layer plus returning moisture that supports new [mould] growth."