Builders who learned healthy building online spent a day on a Northern Rivers site and an evening in Sydney together. What happened in the room says a lot about how practice actually changes.
The blower door was meant to be a demonstration.
Within minutes it had turned into a working bee.
At Wooyung, on the far north coast of New South Wales, a group of builders and an architect stood inside a rammed earth home under construction while a fan pulled air out through the front door. As the pressure dropped, the leaks showed themselves.
Nobody was asked to fix them. People found tape, got to work and watched the numbers improve as each gap was sealed.
It was a small moment. It also captured something bigger: a shift in how some Australian builders are learning to build better homes.
Who was in the room
The visit was organised by Zara D’Cotta, a building biologist and founder of The Healthy Home. She is certified through the Building Biology Institute in the United States as a New Build Consultant and Electromagnetic Radiation Specialist.
D’Cotta started the business in the Northern Rivers in 2020, after her own experience with mould illness and chemical and electromagnetic sensitivity. In 2021, during Covid lockdowns, she launched the Healthy Building Materials Mastermind, an online program for builders, architects and designers. The first in person gatherings followed in 2022.
She now spends much of her time overseas, and recently returned to reconnect with people who have been through her programs. The trip took in site visits around the Northern Rivers and Byron hinterland, an evening at Pro Clima’s training facility in Sydney, and an EMF assessment on a home being renovated.
We have spoken with D’Cotta before about what goes inside the walls. We have also covered why a passive house is not automatically a healthy one. This trip was different. It was less about what she teaches and more about what happens after people have learned it.
A rammed earth home where the learning spread
The Wooyung project will be the home of Chris King of Chris King Constructions, designed with architect Hayley Pryor.
King has completed the Mastermind. According to D’Cotta, the learning did not stay with him. It has carried through to his site supervisor Shep, and Pryor says the project has shaped how she approaches her other work.
That is how knowledge tends to move through this industry. A builder learns something, applies it on a real job, and the people working alongside pick it up.
The visit brought together builders and an architect from Mastermind cohorts running from 2022 to 2026. Some were meeting face to face for the first time.
Image credit: Alexandra Grima
Why airtightness testing matters in a warm, humid climate
Stewart Scholten of Scholten Group brought blower door equipment and ran the test on the day.
According to D’Cotta, airtightness testing is rarely done in the Northern Rivers outside Passive House certification. For many local builders, seeing one on a live project is unusual.
The relevance is practical. Byron Bay and Lismore both sit in NCC climate zone 2, which the ABCB describes as a warm humid summer and mild winter.
In that climate, air leaking uncontrolled through the building envelope carries moisture with it. Where moist air meets a cooler surface inside a wall or roof, it can condense. Condensation is where mould starts.
The NCC has been tightening its approach. Condensation management provisions were introduced in NCC 2019 and strengthened in NCC 2022. The ABCB has noted that well sealed buildings with poor ventilation can carry greater condensation risk, while buildings that are both well sealed and properly ventilated manage it very effectively.
Airtightness is not the goal on its own. Controlled air is.
What is a blower door test?
A blower door test measures how much air leaks through a building’s envelope. A calibrated fan is fitted into an external doorway and used to create a pressure difference between inside and outside, typically 50 pascals. The airflow needed to hold that pressure shows how leaky the building is. Under the NCC’s building sealing verification method for housing, a result of no more than 10 cubic metres per hour per square metre of envelope at 50 pascals demonstrates compliance. The ABCB describes this as broadly equivalent to 10 air changes per hour. Testing before linings go on means leaks can still be found and sealed.
Learning sticks when builders share the work
What stood out at Wooyung was not the final number. It was how the group behaved once the fan was running.
Builders who had studied the theory online were now hunting leaks together, testing ideas against each other and seeing the effect of every fix in real time.
Online learning builds the foundation. Doing the work together is what makes it stick.
Jesse Billington of Billington Projects shows where that can lead. He first joined the Mastermind in 2022 and returned for the 2025/26 program to stay current. D’Cotta says he has grown in confidence, knows when to bring in specialists, and is now attracting clients who seek him out specifically for healthy home builds.
He applied what he learned to his own home and opened it to the public for Sustainable House Day on 17 May 2026.
An evening at Pro Clima
In Sydney, The Healthy Home and Pro Clima hosted an evening at Pro Clima’s Alexandria facility for Mastermind alumni from Sydney, regional NSW and Tasmania.
D’Cotta facilitated a Q&A with Jesse Clarke, Pro Clima Australia’s Technical Innovation Manager, and Daniel Jakobs, known to many builders as Airboss Dan, who leads the company’s builder training across Australia and New Zealand. Clarke has more than 20 years in building envelope performance and contributes to ABCB and AIRAH technical groups.
According to D’Cotta, Pro Clima is also developing an installer certification program for weather resistive barriers. Membrane performance depends heavily on installation, so that is a development worth watching.
Image credit: Alexandra Grima
Healthy building goes beyond the envelope
While in Australia, D’Cotta also carried out an EMF assessment on a home midway through renovation.
Electromagnetic fields are one of the areas building biology considers, alongside materials, moisture and air quality. It remains a less familiar and more debated area for most of the industry. D’Cotta says more builders are informing themselves on it, reducing exposure in their own homes and raising it with clients.
THE GOOD BUILDER TAKE
Most change in construction does not come from a code update or a course certificate.
It comes from builders watching other builders do something well, then trying it on their own jobs.
What this group has built is more than knowledge of materials and moisture. It is a network of peers who test that knowledge on real sites, together. For builders interested in healthier homes, the useful question is not only what to learn, but who to learn it alongside.
Where the real shift happens
Online learning has made specialist knowledge more accessible than ever. That matters, especially for regional builders a long way from training centres.
But the moments that shift practice tend to look like the ones from this trip. A site visit that became a working bee. A Tuesday night that ran well past its finish time.
Online learning builds the foundation. Doing the work together is what makes it stick. That is the part of the healthy homes movement worth paying attention to.
Listen to our earlier conversation with Zara D’Cotta on The Good Builder Podcast, and follow along as we keep covering the builders leading this work.
Thanks to Zara D’Cotta, Chris King, Stewart Scholten, Hayley Priorm and Alexandra Grima (photographer) for their contribution to this initiative and article for our community.
Frequently asked questions
Building biology is a field that studies how the built environment affects human health. It began in Germany, and its name translates as building for life. It looks at materials, moisture, air quality and electromagnetic fields alongside conventional building performance.
Not as a blanket requirement. Under the NCC, builders can show a home is adequately sealed by following the Deemed to Satisfy provisions, or by using the building sealing verification method. That method uses a blower door test, with a result of no more than 10 cubic metres per hour per square metre at 50 pascals. Voluntary standards such as Passive House set much tighter targets.
Air leaking through the building envelope carries moisture. In climate zone 2 areas such as the Northern Rivers, warm humid air moving into walls and roofs can condense on cooler surfaces and create conditions for mould. The ABCB notes that well sealed homes also need adequate ventilation to manage this risk.
It is an online program run by The Healthy Home for builders, architects, building designers and interior designers. It covers the health and environmental impacts of building materials and was launched in 2021.
Related articles
- The materials inside your walls could be making your clients sick
- A Passivehaus is not a healthy house: here is the difference
- Building Better Guide
Last updated: 7 October 2026. NCC references current to NCC 2022; check your state’s adoption of NCC 2025.
General Information Only: This article provides general information only and does not constitute legal, technical or professional advice. Requirements under the National Construction Code vary by building class, climate zone and state adoption. Builders should confirm specific obligations with their building surveyor, certifier or relevant state regulator.
Author: TGB Editorial
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