Building biologist Zara D’Cotta spent years searching for a home that wouldn’t make her sick. What she discovered changed how she works and it should change how builders build.
Most builders care deeply about the homes they deliver. They obsess over details, push back on shortcuts, and take pride in the quality of what they hand over at practical completion.
But there is a category of harm that most builders have never been taught to consider. Not defects. Not delays. Not disputes.
The materials going inside the walls. And what they are doing to the people living inside.
Zara D’Cotta is a building biologist, new build health consultant and electromagnetic radiation specialist who has spent the past five years working directly with builders, designers and architects across Australia and New Zealand. Her mission is simple, even if the science behind it is not: to close the knowledge gap between what gets built and what keeps people healthy.
It started, as many important things do, with personal experience.
A Diagnosis That Changed Everything
At 29, D’Cotta was diagnosed with cancer. Two years later, a melanoma diagnosis followed. The health crises led to a complete lifestyle overhaul, leaving a decade-long corporate communications career and switching focus entirely to health and wellbeing.
But the illness did not stop there. After her cancer treatment, she developed more than 20 symptoms that no doctor could explain. Eventually she learned she was genetically susceptible to mold, and that the stress of her treatment had pushed her to the extreme end of environmental sensitivity.
She spent four years moving from building to building, searching for one that was not water damaged, one that would let her heal.
In 2019, she moved into a brand new build by the ocean in northern New South Wales. She thought it would finally be the answer.
“I woke up after the first night, it was winter time so I’d had all the windows closed, and my eyes were stinging so intensely that I immediately opened all the windows and just had to get out of the house for the morning.”
The rashes and nausea that followed for the first few months prompted a deep investigation into every material used to build her home. What she found was not reassuring.
Synthetic carpets. Polyurethane underlay. MDF cabinetry. Paints. PVC floors. In her words, a toxic chemical cocktail.
Formaldehyde, a known carcinogen, was among the offgassing compounds. Volatile organic compounds linked to hormone disruption, infertility, and developmental issues in children were present throughout. And this was a brand new home.
The Knowledge Gap, Not the Intent Gap
D’Cotta is careful about where she places responsibility. She has no interest in blaming builders.
“It’s not necessarily rogue builders or bad intentions. It’s just that they haven’t been taught. Designers haven’t been taught. It’s just a knowledge gap.”
That distinction matters. The builders putting harmful materials into homes are not trying to hurt anyone. They are using products approved by regulators, products marketed as standard, products that nobody told them to question.
But the gap between regulatory compliance and genuine health safety is wide enough to cause real harm. And the people living in those homes often have no idea why they feel the way they do.
This is particularly concerning for young children, who cannot articulate a connection between their environment and how they feel. As D’Cotta puts it: she is an adult who knows why she is reacting. A baby does not.
The Four Areas Builders Need to Understand
D’Cotta’s work centres on four key areas where standard construction practices create preventable health risks: materials, moisture, air quality, and electromagnetic radiation.
On materials, one of the most common mistakes is builders choosing low VOC products and believing that makes them safe. The problem is that a product can still contain semi-volatile organic compounds including plasticisers, pesticides, antimicrobials and flame retardants while still being classified as low VOC.
“Without full ingredient transparency, it’s really hard to know. I’ve seen a brand being promoted by builders as low VOC and then found out that product actually does contain semi-VOCs.”
On moisture, the trap is trapping it in the building envelope during construction. Timber framing exposed to rain, walls sealed before concrete cures, flooring laid while moisture levels in the frame remain high. The result is mold sealed inside the walls of a brand new home before the client ever moves in.
The electromagnetic radiation piece is where the conversation often surprises people. The electrical code, D’Cotta explains, is designed to prevent shock, fire and injury. It does not take into account decades of research on the biological effects of electromagnetic fields. There is no guidance on where a bedroom should sit relative to power lines, or where a solar inverter, electrical panel or smart meter should be placed.
“There’s no guidance on how close a bedroom should be to power lines or where your solar inverter should be placed. These are things that can contribute to insomnia, headaches, infertility, cancer.”
She tells a story about assessing the home of a doctor and his wife who were not sleeping well. They had a WiFi extender in their bedroom and were sleeping directly behind the electrical panel. The main router was nearby and they were being exposed to millions of microwatts per square metre. When the couple moved the bed to the other side of the room, they immediately slept better.
The Passive House Misconception
One of the more important clarifications D’Cotta makes is around passive house and what it does and does not deliver.
Passive house principles, she says, are excellent. Building science that prevents uncontrolled air and moisture leaks is exactly where the industry should be heading. But passive house is not the same as a healthy home.
“You could have a passive house and have materials that are off-gassing and really high electromagnetic radiation levels. A passive house is not automatically a healthy house.”
This distinction matters for builders who are promoting their work as health-focused. If a client later discovers that their passive house does not meet building biology standards, the commercial and reputational risk lands squarely on the builder.
D’Cotta is also clear about the term healthy home itself. It is not regulated. It means something different to everyone. A home with a sauna and an ice bath is not a healthy home in the building biology sense. Builders using that language in their marketing need to be specific about what they mean and what they have actually delivered.
The Commercial Opportunity
The conversation with D’Cotta is not a rebuke of the industry. It is an invitation.
Builders who understand healthy building principles are not just delivering better outcomes for clients. They are differentiating themselves in a market where clients are increasingly researching who feels safe to build with.
“Builders have more of a significant impact on their client’s health than their family doctor, because the doctor will treat the symptoms and the builder will actually shape the environment that could determine whether those symptoms even occur.”
That is a significant statement. And it comes with a significant commercial implication.
A builder who can genuinely demonstrate that they understand materials, moisture management, electromagnetic exposure and indoor air quality is not just a better builder. They are a harder builder to replace.
D’Cotta runs a Healthy Building Materials Mastermind for builders who want to close the knowledge gap, as well as a Low EMF Home Design and Construction Course for those wanting to go further. She is also developing a Healthy Home Building Blueprint to guide builders from pre-design through to post-construction.
What Good Builders Do Differently
D’Cotta has worked with enough builders over five years to know what separates the ones who act from the ones who do not.
“They’re very humble and willing to put their egos aside and recognise that there’s more that they need to learn. They’re willing to go on a very steep learning curve and challenge their own pre-existing assumptions.”
That willingness to be uncomfortable is, perhaps, what the building industry needs most right now on this topic. The knowledge exists. The research exists. The builders who choose to engage with it are already setting themselves apart.
As D’Cotta puts it, building biology translates from German as building for life.
It is a useful reminder of what a home is actually for.
Listen to the full conversation with Zara D’Cotta on The Good Builder Podcast. Find her work at The Healthy Home.
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