RNZ presenter Kathryn Ryan asked some very good questions in a recent interview about whether all new social housing in New Zealand should be built to the Passive House standard. Here are some clear answers.
Q. What is involved in getting Passive House certification?
A building gets certified as a Passive House if it meets specific performance targets. It can be any kind of building, any kind of design, any kind of material: the standard is not concerned with that. Germans developed this: they focused on one thing (energy efficiency) with laser-like intensity and did it very well. It’s worth pointing out thought that many homeowners will in addition seek out environmentally-friendly materials or methods. Passive House can sit alongside other standards like Homestar or the Living Building Challenge. One ambitious home in Auckland is targeting ratings from all three. They can work together, no problem.
First, it needs to use a very, very small amount of energy for heating and cooling the building. That’s measured in one of two specific ways but the non-technical version is a Passive House will be 90 per cent more efficient than a building that meets the Building Code minimum.
Second, it needs to be highly air-tight and this is measured by a physical test using what’s called a blower door. Air-tight matters because that’s how you keep the warm air inside from leaking out (or in summer, the cool air).
A Passive House requires mechanical ventilation (because no-one wants to live in a sealed box). In a family home, these are small, quiet systems that often sit in a cupboard in the laundry and constantly deliver fresh, filtered air to every room in the house.
Lastly—and this is not widely known—the building needs to overheat seldom if at all. This is increasingly becoming an issue, especially with new homes that have a lot of glazing on the north and/or west walls. I had a client whose expensive new Auckland home was impossible to live in during summer because it gets so hot. This would not happen in a Passive House.
The certification process happens in two phases. First is at the design phase. This is important because if it finds problems, they are far easier and faster to fix in an architectural drawing compared to once the contractors have poured concrete or put up the framing.
Then there’s the post-construction step, where the independent certifier (in New Zealand, that’s usually me) reviews everything down to the tiniest detail to verify that the building was built according to the design and will therefore perform as expected.
Clients (or their architects) don’t pay a little bit more to get a Passive House plaque for the wall. Certification is valuable because it’s really easy to claim your house (or design) is ‘high performance’ but talk is cheap. When a homeowner seeks certification, everyone involved in the project knows they can’t cut corners: all their work will be tested and independently verified. There’s an assurance of quality and the comfort of knowing that your building will perform as intended: you get what you paid for.
Q. Are there barriers to rapidly increasing the number of Passive House buildings in New Zealand?
A. There are three barriers and all of them are people.
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- Clients need to understand why they should insist on a better performing building.
- Everyone involved in the construction sector needs to increase their skills, from architects through to suppliers.
- Councils need reassurance that they can approve superior quality buildings without being exposed to the risk of litigation (avoiding liability is the main focus of building inspectors ever since the leaky homes disaster exploded).
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The biggest single barrier is a lack of educated clients, whether that is a homeowner, property developer or government agency. You can’t see building performance and when it’s optional it can struggle to compete for budget against stone veneer cladding or granite bench tops. For as long as decent performance is optional, clients need to help drive the change.
We also need to grow up and stop being pathologically focused on first costs: how much it costs to build. This is hard when building is so expensive in New Zealand! But there’s a need to think longer term about the ongoing cost of running and maintaining that building.
(I’m always asked, how much more does it cost to build a Passive House? Compared to the crappiest home you can legally get away with, aka it complies with the Building Code. Well, take a longer term view and a Passive House will always be cheaper because of the money you’ll save on running costs. Plus better quality components will last a lot longer. I’m not even going to try to monetise the health benefits. My son has asthma, like so many children in New Zealand. Things like health—being able to breathe freely!—can’t be priced by the market.)
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The second barrier is trained and experienced people in the building sector. I’m talking everyone from architects and designers through to builders and suppliers. PHINZ runs regular training courses for designers and builders and if you pass, you’ll be certified as a Passive House professional. People need to make time for the training, understand its value and be prepared to apply themselves. I’ve hired people with solid maths and architectural skills and it still takes six months and several projects for them to really grasp how this works. You need some technical nous.
There are increasing numbers of architects and designers who are Passive House certified; 32 as of now plus another 20 in training. We need more. There are two shortcuts. First—and this is already happening—an architect can collaborate with someone who brings the PH knowledge to the design, just like they likely collaborate with an engineer. Second, I’m developing standard construction details architects can freely use but they still need an understanding of how to use them and why they need to.
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The third barrier are people that work at councils and at MBIE in code enforcement. Not all of them! The Building Code rests on something called Acceptable Solutions. I like to call this the cartoon guide to building. Often it’s not fit for purpose and MBIE and Council staff know that. But they also know there is no risk to them if they approve a consent application that uses Acceptable Solutions.
Passive House buildings far exceed Building Code minimums in multiple ways. Therefore—ironically—these are not “Acceptable Solutions”. Instead they employ what are called “Alternative Solutions”. Some councils have switched-on staff who are up-to-date with developments in the construction sector and enthusiastic about improving standards. Some don’t.
An example: a concrete slab foundation with un-insulated edges is an Acceptable Solution, so it will fly through consent. Never mind that it bleeds heat out of the house and will, in specific and common conditions, become mouldy. A Passive House slab would necessarily be fully insulated. That’s no longer “Acceptable”. The designer must prove to the council’s satisfaction that it meets all the criteria contained in the Building Code.
So sometimes Passive Houses (and high-performance buildings in general) can take longer to get through the consent stage. In the worst cases, the same Alternative Solution has to be explained to the same council staff members, over and again with every single building consent. That cost is now anticipated by the architect and inevitably gets passed along to the client. In other councils, for whatever reason, these delays don’t happen.
There should not be this variation up and down the country. The solution is two-fold: better educated staff approving building consents and an overhaul of our miserable Building Code. We don’t just need to lift standards, the Code needs to be re-organised. And individual councils should be legally empowered to require or incentivise better than Code minimums. That is plain common sense for a country with as much climatic variation as New Zealand. The current Code recognises only three climate zones which is manifestly inadequate.
So: people are the barriers, and it’s people who can remove those barriers. We need better understanding of the benefits of verifiable high-performance, more training and professional development and an overhaul of the bureaucracy associated with building consents.