Jason Quinn on fixing New Zealand’s building performance

Sustainable Engineering director Jason Quinn says New Zealand doesn’t have a building science problem, but a construction execution one

Jason Quinn spent about a decade at NASA working in propulsion and combustion physics. Seeking change, he took a year off in New Zealand, fell in love with the country, and never left. He soon became one of New Zealand’s first certified Passive House designers, and later its first certified Passive House certifier.

The founding director of Sustainable Engineering, Jason and his team have a deceptively simple mission, applying building science to make buildings healthier, more comfortable and radically energy-efficient. He says we don’t have a shortage of products, materials, or technical knowledge. Instead, we have an execution problem. “We don’t have a building physics problem in New Zealand, or a technology problem,” he says. “We have an execution and constructability problem, and that’s due to an extreme focus on first costs.”

Jason is a leading advocate for Passive House, a standard that has its roots in passive solar design, but has developed into something far more rigorous. Rather than relying on active heating or cooling, the approach uses insulation, airtightness, ventilation and careful design to hold comfortable temperatures with very little energy. One misconception is that it’s simply a rigid checklist of pricey requirements. “It’s just a lens to look through at how you design homes so they perform really well.”

He compares it to NZS 3604. Builders see the timber framing standard as the accepted method for structural performance, not as some ideological movement. Passive House, he argues, is the equivalent framework for thermal performance, comfort and health. “If you want homes that are warm, dry, healthy and accessible for everyone, you end up with something that looks like Passive House whether you call it that or not.”

Early passive solar design often relied on vast expanses of north-facing glazing to harvest winter heat, then somehow retain it overnight. It seldom worked. Passive House relies on detailed modelling to respond to the realities of each design, climate and site, carefully balancing solar energy coming in with minimal heat losses going out. Two sections in the same suburb can need completely different solutions depending on orientation, topography and local climate.

Jason points to his own home, currently being designed on Wellington’s south coast. Despite sitting in the capital, the site loses its winter sun by half past eleven, meaning its thermal requirements resemble a cold Christchurch rather than a north-facing section a few streets away that he would treat almost like Auckland. “When you look at how builders actually build that high-performance house, it’s not crazily different,” he says. Better windows, a little more insulation, careful detailing. “It’s how you put the pieces together.”

Where buildings lose out

Home builds are often driven by upfront cost, while long-term performance is treated as optional. The Building Code, Jason says, shouldn’t be taken as a benchmark. A Passive House targets heating demand below 15 kWh per square metre per year, with the whole home held at a steady 20°C and continuously ventilated with fresh air. In Christchurch conditions, a Passive House next door to a code-built home would use roughly a tenth of the heating energy.

But those benefits are the first to disappear when budgets tighten. Triple glazing becomes double, mechanical ventilation is dropped, roof insulation slips from R6.6 to R5, and the walls thin out to 90mm studs. The builder, he stresses, usually isn’t cutting corners cynically. In their experience, clients care almost entirely about first cost, so they do what they believe is right and get the price down. “Then the client rings me and says their house is cold. I tell them they’ve built a standard code house. Why did you expect anything different?” A code-minimum home, he says, is simply the cheapest building that’s legal. “It costs more because you’re getting more.”

The trap isn’t confined to custom builds gone wrong. A man rang him recently about a 2021 house in Nelson, “not exactly the world’s coldest climate”, that was already miserable, cold and mouldy, and wanted a deep energy retrofit. With its 2021 R-values and double glazing, Jason notes, it was built essentially the way a brand-new house would be built today. The fault was it lacked a ventilation system and was a home left to perform “as the worst it’s legally allowed to.”

Some of those savings never materialise anyway. Take the standard flat ceiling: plasterboard below, battens and trusses above, insulation draped across the top. In theory it sits in still air and performs at its rated value. In practice, wind enters the roof cavity at one end of the building and exits the other, washing through and over the insulation as it goes. “That ceiling is basically R1 if you’re lucky. You paid for R6.6 and got R1, but only when it’s windy.” Faults like that cost very little to avoid and a fortune to live with.

What builders can do tomorrow

In fairness, Kiwi homes are tighter than many assume. A typical new build leaks around six air changes an hour at 50 pascals, against roughly fifteen in Australia, and that from nothing more exotic than plasterboard, plywood and concrete slabs. But even at that level, a closed-up home traps moisture. Surveys show about half of New Zealand homes carry visible mould, worst in Auckland, where mild, damp winters prevent drying.

“If you’ve got windows you can close, you need mechanical ventilation. That’s accepted wisdom everywhere except New Zealand and Australia.” Continuous ventilation manages moisture, thereby preventing damp, rot and mould; heat recovery adds efficiency, but Jason sees health as the main prize, with superior indoor air quality having instant health benefits in some cases. Retrofitting a system later, he says, costs far more than building it in.

For a builder who wants their next house to perform better without chasing certification, Jason suggests three changes that cost little beyond attention. The first is airtightness: treat the internal lining as a continuous air-control layer, seal the penetrations through the ceiling, and keep the plasterboard unbroken behind the bath, where it’s so often left open over a void. “A few hundred dollars of labour, no new products, can save 10 to 20% of the heating bill.” The second is wind-tightness: walk the outside of the building and close off every path the wind can take through the insulation.

The third is continuous ventilation, often as simple as swapping the bathroom extract fan for a continuous-extract model, frequently cheaper than the standard unit at Bunnings, that runs quietly around the clock. Passive doesn’t mean a sealed box. With its ventilation running, a Passive House has more fresh air than an ordinary home, and because it warms faster, the people inside tend to throw the windows open in spring before their neighbours do. “Homes are supposed to be sanctuaries,” he says, “not somewhere you scrape through life on the least you can get away with.”

There is a caution. Adding high-performance products in a build you haven’t modelled can be a double-edged sword. Jason points to a recent UK external wall insulation programme with an alarming failure rate, driven, he says, by chasing energy savings at the lowest possible cost, with predictable results. The fix is knowledge, which is where the industry’s next generation comes in. Sustainable Engineering offers a certified tradesperson course and Master Builders Canterbury has funded scholarships to send apprentices through it.

Could every home be a Passive House one day? Jason thinks so, because it’s simply what a decent home is. And, unlike most upgrades, it pays back from day one in lower bills and better health. The technology and the products are already here, he says. What’s missing is the will to put the pieces together properly.