If winter nights have you waking up to condensation dripping down your windows, you’re not alone – Australian homes are infamously humid and poorly ventilated.
Arianna Brambilla, an associate professor at the indoor environmental quality lab at the University of Sydney, says Australian homes were designed for heat, not moisture management.
“A home that cannot stay warm in winter is a home where cold surfaces are creating condensation, and condensation is how moisture accumulates in walls and building cavities over time,” Brambilla says.
Beyond being difficult to manage – and live in – a humid home can adversely affect our health.
What are the health implications?
Brambilla says the health consequences of living in a persistently humid home can be serious and compound over time, and often affect those who can least afford to deal with them.
Dampness is associated with a range of respiratory issues. “The evidence is unambiguous. Dampness and mould exposure are associated with asthma, wheeze, cough, bronchitis, and other respiratory conditions in both adults and children.”
According to Brambilla, when relative humidity exceeds 70 per cent, dust mites thrive and pose a threat to immunocompromised people, as mould can present a risk of fungal infection.
About one in five Australians has allergies, including most people with asthma, and one of the most common triggers is mould as an allergen or irritant. Sheryl Van Nunen, National Asthma Council Australia spokesperson and allergist, says damp conditions promote mould growth.
“Mould can act as an irritant in our nose, sinuses and lungs. Mould prepares the food for the house dust mite, the world’s most common allergen affecting noses, sinuses and lungs,” she says.
Van Nunen agrees that the health effects of a damp home can seem mild but should be taken seriously.
“The cumulative effect of wheezing and nasal blockage results in poor sleep, which can increase the likelihood of catching a respiratory virus, which, in turn, can worsen any rhinitis or asthma. It also reduces the ability to perform tasks safely, including driving,” she says.
Brambilla says beyond respiratory issues, there is evidence that inhabiting a humid, damp or mouldy home can negatively affect a person’s mental health.
“A review found consistent associations between mould exposure and depression, anxiety and stress across adults and children. Visible mould in the home was associated with mentally unhealthy days.
“Living in a home that smells bad, looks damaged, and makes you or your children unwell is genuinely distressing, and the evidence now shows this translates into measurable harm to mental health,” Brambilla says.
How to understand humidity levels
The target range for indoor relative humidity is 40 to 60 per cent. This range is grounded in World Health Organisation guidance and forms the basis of widely used indoor environmental quality standards, says Brambilla.
When humidity climbs above 60 to 70 per cent on a sustained basis, mould, dust mites and certain bacteria can grow rapidly.
“For a definitive reading, a hygrometer is inexpensive and widely available online and at hardware stores. Many smart home sensors now measure temperature, relative humidity, carbon dioxide and particulates in a single device,” she says.
However, a single reading is not as accurate as one taken over a longer period of time.
How to dehumidify your home
If you are regularly waking to condensation on your windows, it is your building trying to tell you something, Brambilla says.
“Other signs [of high humidity] include: a persistent musty smell even after cleaning, visible mould growth … peeling or bubbling paint, wallpaper lifting at seams, and warped or swollen timber,” she says.
Most commonly, the occupant of the home is responsible for managing humidity, which works well in mild weather, according to Brambilla, but breaks down when it matters most: in winter, when people close up their homes to stay warm, trapping moisture inside.
“Cooking, showering and drying clothes indoors all release significant quantities of water vapour. A single load of washing dried indoors can put close to two litres of water vapour into the air. Without adequate ventilation that moisture has nowhere to go except into building surfaces,” Brambilla says.
How to dehumidify your home, according to experts:
- Remove visible mould with diluted 1:10 white fermented vinegar.
- Remove wet carpets.
- Treat rising damp as soon as it is discovered.
- Use extractor fans in bathrooms, kitchens and laundries to aid natural ventilation and reduce the likelihood of mould growth.
- Use a dehumidifier to remove moisture and/or an air purifier with a HEPA filter to reduce airborne mould spores.
- Remove indoor pot plants as they can promote mould growth.
- Seal any leaks in bathrooms and roofs.
- Wipe condensation off windows and sills.
“The key to better air quality in the home in winter is to manage humidity and ensure any ventilation is helping to improve the quality of the air you breathe, not hindering it,” Brambilla says.
The problem is underreported and normalised by many Australians, she says.
“They see it appear each winter, clean it off, and watch it return, without necessarily understanding that it is a health risk or that it reflects a building failure rather than a cleaning failure.”
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Abby Seaman is a digital producer and lifestyle writer at The Sydney Morning Herald.Connect via email.
