Mould Prevention and Air Quality in Australian Homes

Mould is a persistent challenge in many Australian homes. Our humid coastal climate, combined with housing designs that sometimes prioritise aesthetics over ventilation, creates perfect conditions for mould growth. Beyond being unsightly and damaging to property, mould poses genuine health risks, particularly for those with respiratory conditions, allergies, or compromised immune systems.

This guide explores the relationship between mould and indoor air quality, and provides comprehensive strategies for prevention and management in Australian homes.

Understanding Mould

Mould is a type of fungus that reproduces through microscopic spores. These spores are virtually everywhere in our environment—indoors and out. When spores land on damp surfaces, they can begin growing, forming the visible colonies we recognise as mould.

Mould requires three things to grow:

• Moisture: The critical factor—without adequate moisture, mould cannot survive
• Food source: Organic materials like wood, paper, fabric, carpet, and even dust
• Suitable temperature: Most moulds thrive between 15-30°C—comfortable living temperatures

Health Impacts of Mould Exposure

Mould affects health primarily through airborne spores and fragments that we inhale. Health effects vary based on exposure level and individual sensitivity:

Common Symptoms

• Nasal congestion and runny nose
• Eye irritation (redness, itching, watering)
• Coughing and throat irritation
• Skin rashes and irritation
• Headaches and fatigue

Serious Health Risks

• Asthma attacks and worsening of existing asthma
• Allergic reactions in sensitised individuals
• Respiratory infections, particularly in immunocompromised people
• Hypersensitivity pneumonitis (lung inflammation)

Common Problem Areas in Australian Homes

Mould tends to appear in predictable locations where moisture accumulates:

Bathrooms

The most common mould location due to high humidity from showers and baths. Look for mould on ceiling corners, around shower recesses, on grout lines, and behind bathroom cabinets.

Kitchens

Steam from cooking and dishwashing creates humidity. Mould often appears under sinks where leaks occur, behind refrigerators, and around rangehoods if ventilation is poor.

Laundries

Washing machines and dryers generate significant moisture, especially if vented indoors. Check behind machines and around any plumbing connections.

Bedrooms

We release moisture through breathing and perspiration while sleeping. Bedrooms with poor ventilation, furniture pushed against cold walls, and heavy curtains blocking airflow are vulnerable.

Subfloors and Crawl Spaces

Poor drainage and rising damp can create chronically moist conditions. This moisture can migrate up into living spaces.

Prevention Strategies

Control Humidity

This is the most effective mould prevention strategy. Aim to keep indoor relative humidity between 30-50%.

• Use exhaust fans: Run bathroom fans during and for 20+ minutes after showers. Use kitchen rangehoods when cooking.
• Ventilate: Open windows when outdoor humidity is lower than indoors. Cross-ventilation is most effective.
• Dehumidifiers: Essential in chronically humid spaces or during prolonged wet weather.
• Air conditioning: Cooling air reduces its moisture-holding capacity, effectively dehumidifying. Ensure your AC unit is properly maintained.

Address Moisture Sources

• Fix water leaks immediately, no matter how minor
• Ensure proper drainage away from building foundations
• Vent clothes dryers outdoors, never into the house
• Don't hang wet laundry indoors (or use a well-ventilated area)
• Use lids when cooking to reduce steam

Improve Air Circulation

• Leave gaps between furniture and walls, especially on external walls
• Open wardrobe doors periodically to prevent stagnant air
• Use ceiling fans to maintain air movement
• Consider running an air purifier to promote circulation

Design and Material Considerations

• Use mould-resistant paints in high-humidity areas
• Consider hard flooring rather than carpet in moisture-prone rooms
• Ensure adequate insulation to prevent cold spots where condensation forms
• Install proper vapour barriers where needed

The Role of Air Purifiers in Mould Management

Air purifiers can be valuable tools in your mould management strategy, but with important caveats:

What Air Purifiers Can Do

• Capture airborne mould spores: HEPA filters effectively capture mould spores (typically 2-10 microns) from the air
• Reduce inhalation exposure: By removing spores from breathing air, purifiers can reduce symptoms in sensitive individuals
• Help prevent spread: Capturing spores can prevent them from settling on new surfaces

What Air Purifiers Cannot Do

• Kill mould: HEPA filters capture spores but don't kill them
• Remove existing mould: Surface mould must be physically cleaned
• Solve moisture problems: If humidity remains high, mould will continue to grow regardless of air purification

Think of air purification as a complementary strategy, not a primary solution. Address moisture sources first, then use air purifiers to reduce airborne spore levels.

Cleaning Mould Safely

For small mould occurrences (less than 1 square metre), you can often clean it yourself:

Safety Precautions

• Wear a P2/N95 mask, gloves, and eye protection
• Ventilate the area well during and after cleaning
• Contain the area to prevent spore spread
• If you have respiratory conditions, consider having someone else do the cleaning

Cleaning Process

1. Wipe surface with damp cloth dipped in diluted detergent solution
2. Rinse with clean water and wipe dry
3. Dispose of cloths in sealed bags
4. For hard surfaces, white vinegar or commercial mould cleaners can be used
5. Ensure the area dries completely

Bleach is sometimes used but is less effective than widely believed—it kills surface mould but doesn't penetrate porous materials. It also doesn't prevent regrowth if moisture conditions remain.

Seasonal Considerations for Australia

Summer (December-February)

High humidity in coastal areas makes this a challenging season. Use air conditioning not just for cooling but for dehumidification. Be particularly vigilant about bathroom and kitchen ventilation.

Autumn (March-May)

Transitional weather can bring unexpected humidity spikes. As homes are closed up more, ensure mechanical ventilation is adequate.

Winter (June-August)

Cold surfaces lead to condensation, especially on windows and external walls. Unflued gas heaters add significant moisture to indoor air—consider alternative heating if mould is a problem. Morning condensation on windows is common.

Spring (September-November)

Spring rains and warming temperatures can create ideal mould conditions. Check for any water intrusion issues before conditions become conducive to mould growth.

Long-Term Strategies

For homes with persistent mould issues, consider these longer-term approaches:

• Building inspection: Identify hidden moisture sources or structural issues
• Improved ventilation systems: Mechanical ventilation can provide controlled air exchange
• Whole-house dehumidification: Integrated systems for chronically humid homes
• Waterproofing improvements: Address exterior drainage and damp-proofing
• Climate-appropriate design modifications: Consider professional advice on improving your home's moisture management

Conclusion

Mould prevention in Australian homes requires ongoing attention to moisture control. By maintaining appropriate humidity levels, ensuring adequate ventilation, addressing water issues promptly, and using air purification as a complementary tool, you can create an indoor environment that's inhospitable to mould growth.

Remember that mould is a symptom of a moisture problem. While cleaning visible mould is necessary, lasting prevention requires addressing the underlying conditions that allowed it to grow. With consistent attention to indoor air quality and humidity management, you can protect both your home and your family's health from the effects of mould.