How do you stop mould and condensation?
If you have been watching the news lately, mould fever is hitting Australia hard. Homeowners are terrified of sick building syndrome, and for good reason. For decades, we accepted the leaky tent as the Australian standard. But as the building code changes, we are heading toward a much more dangerous reality.
The most dangerous advice you will hear in this industry is that a house needs to breathe. It is rubbish. Your house isn't a living thing; you are. When people say a house needs to breathe, they usually mean they are terrified of trapping moisture. But relying on gaps in your floorboards and leaky windows to ventilate your home is like trying to filter your air through a dusty, wet sponge.
The New CSIRO Reality: The Semi-Sealed Trap For years, we pointed to CSIRO data from 2015 showing the average new Australian home was a sieve, leaking at roughly 15.4 ACH. But the game has moved on.
A major study released recently shows that new 6 and 7-star homes have tightened significantly, now averaging between 7.0 and 8.0 ACH. While 7.5 ACH sounds better for your energy bill, it is actually the worst possible result for your health. These homes are tight enough to trap moisture and CO2, but they aren't tight enough—or ventilated enough—to let that moisture escape.
Australia is currently following the exact roadmap that led to the 23 billion dollar leaky building syndrome disaster in New Zealand.
The Stats: A National Health Crisis The link between building physics and your family’s health is undeniable:
The Petri Dish: It is estimated that up to half of Australian homes are currently affected by indoor mould.
The Asthma Link: Living in a damp home increases the risk of childhood asthma by up to 53%.
The NZ Warning: In the 90s, New Zealand tried to make homes tighter for energy efficiency but ignored ventilation. The timber frames rotted in silence, costing 23 billion dollars to fix.
The Solution: The 4 Ds of Weather Tightness At Carland Constructions, we don't build to the minimum code—we build to the Passive House standard. Every one of our projects, like the Forrest Certified Passive House (Spotswood), uses a tiered risk-management strategy called the 4 Ds to ensure your home is a 100-year legacy.
Deflection: This is our first line of defence. We use eaves and high-performance cladding to keep the bulk of rainwater away from the structure. If water never touches the wall, it can't cause a problem.
Drainage: No matter how good your cladding is, some water will eventually get behind it. We install a weather-resistant barrier behind the cladding to catch any bypass and direct it down and out of the building.
Drying: This is the step most builders miss. We create a 35mm ventilated cavity using vertical battens. This air gap allows a constant flow of air to enter at the bottom and exit at the top, wicking away moisture and keeping the timber frame bone-dry.
Durability: We use high-quality membranes like Intello and vapour-permeable wraps that act like a high-end Gore-Tex jacket. It stops the rain but allows water vapour inside the wall to dry out to the exterior.
Mechanical Ventilation: The Active Lungs In a tight home, you need active lungs. Our Mechanical Ventilation with Heat Recovery (HRV) brings in fresh, filtered air 24/7 while expelling stale, moist air. It removes dust and pollen, ensuring the indoor air is actually healthier than the air outside.
To compare the results, our Forrest Certified Passive House (Spotswood) achieved 0.41 ACH. This is nearly 20 times tighter than the new Australian average, but because it is paired with an HRV, it is infinitely healthier.
The Bottom Line If your builder tells you a house needs to breathe, they are admitting they don't understand building science. Australia is at a crossroads: we can either keep building leaky tents that rot, or we can embrace the Passive House standards that protect our families.
As a Certified Passive House builder Melbourne families trust, we don't guess that your home will be healthy; we prove it.
Ready to stop settling for a glorified tent and start building high performance homes Melbourne families deserve?