At Toa Homes, our journey to create healthier homes for Aotearoa began with a simple question: If we want to improve health outcomes for whānau, what needs to change in the way we build houses?

Over three years, our team embarked on a mission to develop a construction system that can fundamentally change how homes are built in Aotearoa by delivering homes that meet the World Health Organisation’s healthy home standards, without compromising on affordability or design flexibility.

"We didn't just want to build another house," explains James Bushell, Toa Homes general manager. "We wanted to create homes that work better for the people of Aotearoa. We need warmer, drier, healthier spaces that don't cost the earth to build or heat and maintain in order to impact multi-generational health outcomes."

From day one, we set ambitious goals. We wanted to create homes that meet or exceed the World Health Organisation’s Healthy Home Standards. We wanted exceptional air-tightness and effective vapor diffusion. We wanted to eliminate thermal bridging. And perhaps most importantly, we wanted a system anyone can build with, using readily-available, locally-sourced materials and low waste.

Breaking it down and building it back up again

To shift the way things are done, in a lasting and meaningful way, we decided to take a first principles approach. First principles is a problem-solving strategy that helps break down complex problems into fundamental parts. We started with the aim of improving health outcomes, which pointed back to housing. Then we broke the complex challenge of housing quality down into parts, by asking questions to understand why the system is the way it is, discarding our assumptions and conventions, and rebuilding from the ground up using ideas from different fields.

This approach required us to bring everyone to the table to form our research and development team, including engineers, architects, builders, prefabrication specialists and sustainability experts. We met regularly over the three years to ideate, test and adjust our thinking through experimentation.

Zak Read, our operations manager and experienced builder, remembers those early meetings well: "We'd have these conversations that went round and round. The designer or engineer would present solutions, and I would either push back or validate based on what I knew would work on site. That honest back-and-forth led to solutions that worked both on paper and, eventually, in the real world."

As a result of this approach, we developed a collection of design principles that spoke to our values as a business and addressed the challenges we’d need to overcome to deliver a successful product in a saturated market. These principles provided us with an additional set of constraints to guide our research and development.

- Entry-level build costs from $3800 per square metre
- Minimal active heating and cooling, significantly reducing energy costs
- Reduced healthcare costs, due to living in healthy home
- Design flexibility
- Fast and accurate assembly
- Predictable performance and durability
- Local, easy-to-access materials
- No specialist tools or technology required to construct
- Capable of meeting Passivhaus standard
- Low carbon emissions and embodied carbon
- Natural and recycled materials
- Minimal waste
- Durable and safe materials

Working in this highly collaborative and outcome-focused way wasn't always easy, but it was essential. By challenging each other and respecting different perspectives, we were able to balance our design principles without compromising on the ultimate outcome of a healthy home. After three years of going through this process, we landed on something truly innovative.

Our panel system represents a significant departure from traditional structurally insulated panels (SIPS). Instead of relying on the insulation for structural integrity, our panels derive their strength from the panel itself, which is made out of recycled and natural timbers and packed with recycled glass insulation.

"What this means for homeowners," our lead engineer points out, "is that you have the flexibility to upgrade insulation in the future without compromising the structure of your home. We're building for today with tomorrow in mind."

Testing, testing and more testing

We found by testing our materials and process over and over and over again, we were able to make incremental improvements that, together, led to the health outcomes we were designing for.

Our testing approach was methodical. We started with bare panels, then sealing window openings, then testing with windows installed, and finally conducting whole-house testing. This systematic approach allowed us to identify and fix specific issues at each stage. All up, our pilot house underwent more than 20 blower door tests at different stages of construction, far beyond industry standard.

"Getting air-tightness right on a small build is way harder than on a larger one," Zak explains with a laugh. "You've got less volume of air and practically no margin for error. But we were committed to getting it right."

One of our breakthrough moments came when we began experimenting with finger-jointed timber products. As Zak notes, "With a recycled, lighter-weight product, we actually achieved stronger and more accurate results than traditional timber." The shorter grain lengths minimise bowing and twisting, which is critical for maintaining the dimensional stability of our panels.

The first generation of panel designs used oriented strand board (OSB), which met our sustainability requirements but after a great deal of testing didn't end up meeting our exacting standards for air-tightness, so we changed tact. This led to our second-generation panel system, using a different combination of air barrier materials, in addition to improved service cavity design, and more flexible panel dimensions.

Putting it into practice

Once we were confident in the structural integrity and performance of the panels, we tested our build process on our pilot house — a 32 square metre house, which our general manager and his whānau ended up purchasing as their first kainga.

We built the pilot house in the factory so we could conduct the rigorous testing and make adjustments to the panel construction and our build process along the way in a controlled environment. In the end we ended up surprising ourselves with the efficiency of building and constructing using the panels, managing to get the entire panel production process down to one day, with basic structure assembly completed in one hour.

Transporting the pilot house to site and installation highlighted the structural integrity of the panel system. To get the pilot house to site we needed to pull it up a narrow, windy gravel goat track with a rock wall on one side and steep cliff on the other.

“The driver of the truck and front loader were incredible,” says Zak. We expected it to take a full day to get the house up to the site, and he had it up there in less than an hour, expertly navigating exceptionally difficult conditions.”

Once we got the house on site, we found that the structure of the house hadn’t moved — not even a millimetre. The panels provided exceptional structural integrity for the house, which just reconfirmed the testing and testing again was worth the time and effort.

Looking forward

The learnings from our pilot project have driven further improvements to the panel system. We've increased ceiling heights, introduced a keystone panel for improved assembly, refined panel increments for greater design flexibility, and improved the materials we use for air permeability.

But we're not stopping there. Our team will continue to explore alternative insulation materials, develop additional panel configurations, optimise production processes, improve connection details and respond to feedback from architects and builders.

"What excites me most," our general manager reflects, "is that every improvement builds on what we've learned. We're creating homes that are healthier for people and better for the planet — and we're doing it at a scale that can make a real difference for New Zealand."

Building a healthier Aotearoa

For us, this journey isn't only about innovative construction techniques, they’re just a means to an end. Looking at the whole building process, from the materials we use and the way we assemble homes, was essential in order to reach a much-needed outcome — building homes that are truly healthy, at a price point that is competitive with building to the NZ building code minimum. Homes that stay warm and dry without costing a fortune to heat, where the air is clean and free from harmful chemicals, pollutants and allergens. Homes that last longer and perform better, year after year. And most importantly, homes where both the people of Aotearoa and Papatūānuku can thrive for generations to come.

Our pilot house, with its solar power, battery storage, rainwater harvesting, and mechanical ventilation with heat recovery, represents our vision for the future of housing in Aotearoa.

We invite you to join us on this journey and make a commitment of doing better for the people and places we love.

In pursuit of healthier homes: Behind our innovative panel system