Initial design: putting all the pieces together

31 July 2022 by Jason Quinn

Make the right decisions about fundamental building components

The understanding and enthusiasm for high performance buildings is gathering momentum. More and more homeowners are understanding that the Building Code is inadequate and that their new build should perform like a superstar, not just look like one.

This is good. And this enthusiasm is creating new problems, like I talked about in my recent rant that called for an end to “cargo-cult architecture”. We now have more than 40 architects and architectural designers in New Zealand who are certified as Passive House designers or consultants. But many more are looking to improve the performance of the buildings they design. Sometimes their best intentions are ineffectual: they cost the client lots more money but deliver very little additional performance benefit. Or, they introduce a whole new set of problems: sure it’s warm in winter, but the house is an uninhabitable oven in summer.

This heating demand graph contrasts the amount of energy needed each year by different iterations of the design. It is specific to each Initial Design report. The NZ Building Code is provided as a baseline comparison. #2 is the design as currently specified. #3 shows the difference made by adding low solar heat gain glazing and adding a mechanical ventilation heat recovery unit.

I often see the push for better thermal performance coming from the client. They want better-than-Code performance. There are various suppliers keen to tell them about their excellent products. But as one person told me recently, “I’m buying all this stuff and I don’t have anyone putting all the pieces together.”

There is relentless attention on how much extra it costs to build to Passive House performance. It’s very unfortunate that some clients are spending as much as certified Passive House performance would cost but getting nothing like that much benefit. In these cases, intentions are good but decisions are misguided, due to inexperience or lack of training . (If you haven’t read that cargo-cult article, please go read it now.)

As this business gets busier, I’ve been hiring and training staff, systematising what we offer and working out how to explain it. This series of articles—you’re reading Part I of IV*—is an attempt to do that. I’m going to explain what we call the Initial Design phase. You don’t have to hire us to do this, but understand the work involved and make sure someone is doing it. Someone qualified, someone independent.

Here’s what we contribute during the Initial Design phase (it’s the first of four; some clients hire us for this first stage only). We review the architectural plans (floor plans, elevations and site shading) and model it using several different types of software. This modelling is crucial. Individual suppliers can tell you about what their bit of the house does (windows, wall assemblies, insulation etc etc) but someone must check how all the different components work together. Modelling makes it possible to predict how the overall building will perform—before it is built. It is always cheaper to fix problems on paper compared to on the building site!

We take into account specific details about your climate. My book goes into the inadequacy of three official climate zones for a country that spans such latitude and elevation. Passive House modelling uses 19 different zones, giving much more accurate results. Here’s good news for people building in Auckland (or Northland): it really doesn’t take much to get your build up to Passive House standard. Double-glazing is almost always sufficient (it’s required by the Code anyway) and it’s entirely suitable to use a traditional timber frame that every builder in the country is familiar with constructing. In those mild climates, you don’t need to modify that wall assembly very much to achieve a whole lot better level of performance. But you can’t expect someone trying to sell you complex wall assemblies or joinery to tell you that.

The Initial Design review will give you confidence that the building will perform to your expectations, whether you’re the architect or the client. Often it is the client who hires us but some architects are also calling us in. If they do not have Passive House training, we can be the nerds that run the numbers and give them some hard data to back up or direct their choices. The report we write will highlight any issues, outline how to mitigate them, advise on mechanical ventilation with heat recovery (MVHR) and provide helpful graphs that make it easy to see how different products will perform. (MVHR, by the way, is not a nice-to-have extra: even Building Code minimum houses need ventilation systems.)