It’s hard to feel optimistic about the likelihood of bold change to address climate change and human health, welfare and equity right now. But from a technical perspective, it makes sense to take aim at the root of the problem of New Zealand’s in general poorly performing, unhealthy buildings and change the Building Code itself.
I had to gloss over this part of my presentation at the PHINZ conference in September, so I thought to unpack it in more detail in a technical article. Jess Berentson-Shaw’s presentation at the same event has certainly got me thinking. Her research lays out ways we can effectively talk about change and gather support for our goals. I necessarily approach problems from an engineer’s perspective, looking for the most efficient and effective ways to solve a problem. With regard to the low legal minimum requirements for buildings in New Zealand, I think we must take aim at the legislation itself, as laid out in the Building Code. This is not how the problem has been addressed in recent times.
Prior to the last election, MBIE was consulting on and designing step changes to the minimum building standards. For all that we talked about the building code, we’re actually talking about Acceptable Solutions, which is just one part of the framework a couple of levels down. The following graphic illustrates that very well.
The Building Act 2004 is the primary legislation governing the building and construction industry. It largely replaced the Building Regulations 1992 but it kept the Building Code, which was a schedule included in the older legislation. (All explained in more detail here and the Building Code can be seen here as the stub that remains of the 1992 legislation.)
Since the changes rolled out throughout 2023, new buildings need to be better insulated. But as slow and complicated as this process might have seemed to those of us championing improvements, the change was effected by the most expeditious route: changing the regulations rather than an act of parliament. In this conversation I’m not talking about changing the Acceptable Solutions or even the Verification Methods, although these do need updating. My focus is on improving the Building Code itself!
The Building Code does not concern itself with ‘how to build’. It’s purely performance-based. It includes phrases like “facilitate efficient use of energy” and then specifies functional requirements like “buildings must be constructed to achieve an adequate degree of energy efficiency…” and finally performance requirements such as, “the building envelope enclosing spaces where the temperature or humidity (or both) are modified must be constructed to (a) provide adequate thermal resistance…”.
There are two primary issues with the approach as written. The first is that the sections do not adequately account for interrelationships between the code sections. Second, the performance criteria reference “adequate”, without definition of what adequate means in each context. This is insufficient guidance.
Let’s consider for example the necessary interaction between humidity and temperature. My conference presentation was primarily focused on the research I’d undertaken into fRSI requirements in the New Zealand context. My conclusion was that, although fRSI requirements vary a lot throughout the country due to climatic differences, in general in order to prevent mould buildings must be ventilated and heated. In general, New Zealand homes aren’t run in a way that provides enough of either.
I went into a lot of technical detail about fRSI in a previous technical article—what it is and why it matters and the implications for design. So I won’t rehash that here. Suffice to say interior relative humidity has to be controlled. Surfaces with lower fRSI are colder and have higher relative humidity on the surface and that’s a recipe for mould. Mould is a problem, for buildings and the people inside them. In many climates in New Zealand, even infinite ventilation won’t control relative humidity if the building is not also heated adequately.
The current Building Code does not recognize these vital interrelationships. But between current building physics and decades of public health research, we have the knowledge to make these linkages and meet the challenge of defining adequate. Right now, an undefined ‘adequate’ permits construction of mouldy buildings that meet the Building Code requirements and that just isn’t OK. It’s difficult to legislate against stupidity, especially of the wilful kind. But you also can’t argue with physics. Give performance targets a physical defined meaning. Note that my proposals below are not about making Passive House levels of performance the minimum requirement. Far from it. The intention is to prevent the building of crap houses that are not fit for purpose.
So here’s my conversation-starting take on how the Building Code performance-based language could define adequate by cross-referencing other requirements. (Yes this makes for more complex legislation, but that’s why we have public servants with expertise in the specific art of drafting legislation.)
I expect my proposal to include reference to heating costs as a percentage of net income to be most controversial but from any kind of broad perspective that values human health and happiness, it is nuts to keep building new homes that bake in fuel poverty for generations.
The same argument extends naturally to cooling costs: heatwaves kill people and we’re going to have more of them in coming decades. There is nothing in the Code or regulations that requires developers to avoid overheating so in general there is no modelling done to check. The results can be pretty awful. I’ve been involved in projects where the modelling showed the house will overheat more than 50% of the time; you can take that as meaning the house will be over 25C the entire summer, day and night. The point of modelling is to identify problems and their solutions. This case would be fixed with external moveable shutters. But the client wants to just run his (PV-powered) air-conditioning all the time. That’s not a solution that transfers to social housing in south Auckland. So G5 needs some work too—what do readers think about how this could be tackled? It seems like a whole new clause needs to be added.