We’ve spoken before about how our principal designer, Simone, has asthma and is highly sensitive to mould. In fact, we sometimes joke that we could hire her out as a human mould detector!

But on a more serious note, Simone’s sensitivities have made her a powerful advocate for building homes that don’t just look good — they’re truly healthy to live in.

Recently, we had a project in Northcote where this issue became strikingly clear.

When a Renovation Reveals a Rotten Truth

Our client had purchased an older home with the intention of giving it a new lease on life — renovating and extending it to meet the EnerPHit standard (the Passive House standard for retrofitting existing buildings). As someone with a building background, he was planning to do much of the work himself.

But as he began peeling back the layers — removing old plasterboard and flooring — the real story of the house began to emerge.

The structure was riddled with problems. Studs and floor joists were severely damaged by both termites and long-term water ingress. Rot was widespread. Worst of all, the entire home was contaminated with mould — not just surface mould, but deep into the structure, where it had festered undetected for years.

An Allergic Reaction in Real Time

Simone visited the site to workshop the design brief with the client. But during the visit, something alarming happened — and it happened quickly.

It started with a tickle in her throat. Then a runny nose. Itchy eyes. Within an hour and a half, Simone was scrambling for an antihistamine. Her throat was sore, her eyes were red and watery, and her body was clearly reacting to something in the environment: mould.

Of course, not everyone reacts to mould exposure as quickly or obviously. But many people do — especially those with asthma, allergies, eczema, or compromised immune systems. Children and elderly people are particularly vulnerable. And often, the symptoms are subtle: a persistent cold that never seems to go away. Chronic fatigue. Irritated skin. Sleep issues. Ongoing respiratory problems.

The Scary Thing About Mould: You Often Don’t See It

In most homes, mould isn’t on the surface. It hides. It can sit silently behind walls and under floors for years, often going completely unnoticed — until someone gets sick or serious damage is uncovered during a renovation.

Imagine if our client hadn’t opened up the walls. Imagine if he’d just painted over the existing surfaces, put in a new kitchen, and called it a day. The new owners would have moved into what looked like a freshly renovated home — but behind the walls, the air they breathed would be mould-laden and toxic.

What You Can Do

If you or a family member has persistent symptoms — coughing, congestion, skin irritation, headaches — and you can’t quite work out why, it might be time to get your home checked for mould. A qualified building biologist is a good place to start.

And remember: mould can’t be killed with vinegar or bleach alone. Surface cleaning might remove stains, but the spores often survive and keep spreading.

How Passive House Protects You

This is where the passivehaus standard makes such a difference.

By design, Passive House principles work to prevent the conditions that mould needs to grow:

🔹 Airtight construction stops moist outside air from seeping into walls and ceiling spaces.

🔹 Continuous insulation ensures there are no cold surfaces where condensation can form.

🔹 Mechanical ventilation with heat recovery (MVHR) continuously brings in fresh, filtered air — and expels stale, humid air — without losing heat or cooling.

🔹 Thermal-bridge-free construction means no sneaky cold spots inside walls where moisture can condense.

All these features work together to create an indoor environment that is dry, well-ventilated, and resilient to mould — by design.

Simone lives in a Passive House herself and has experienced the benefits firsthand. After years of struggling with asthma and allergies, she’s now almost symptom-free. Even her children seem to get sick less often, or bounce back much quicker when they do. Coincidence? We don’t think so.

Final Thoughts

Mould is more than just an unsightly stain. It’s a health hazard that can quietly compromise the well-being of everyone in your home.

The good news? It doesn’t have to be this way.

With smart design, quality construction, and a focus on health, we can build homes that don’t just look great — they help you live better.

Because your home shouldn’t make you sick. It should help you thrive.

💬 Have questions about Passive House, mould, or indoor air quality? Get in touch — or check out our Healthy Home Guide via the link in bio.