I hear this quite a lot! But, I’m owner building a certified Passive House in Perth. And that’s Perth, Western Australia, not Perth, Scotland. Have I lost my mind? No, I have not. I mean, it’s a matter of taste, Passive Houses cost more to build, and there’s a whole debate to be had about their various costs and benefits, in no way am I suggesting it is the right approach for everyone.
But, this particular objection, that I hear all the time? “Passive House is only relevant in a German climate”? Nope. Nope-de-nope. Not the case at all. That idea is based on a big misunderstanding of what a Passive House actually is.
What is a Passive House?
A Passive House (or Passivhaus) is a very comfortable, very energy-efficient house that has been independently certified by the Passive House Institute in Germany.
It is ‘passive’ in the sense that it delivers a lot of comfort without using a lot of fuel and energy to achieve that. (And a Passive House is a different thing from a house which uses ‘passive solar’ design – although good passive solar design is indeed one of the cornerstones of successful Passive House design).
“The German climate is completely different”
Yes it is. German homes have to deal with winter cold that is not relevant in Perth. But is it a more extreme climate? Perth homes have to deal with summer heat that is not relevant in Germany. I’m writing this at the end of a Perth February with seven days of at least 40C. Ten degrees below freezing is not my preferred indoor temperature, but neither is 40C.
Strangely enough, it’s the cold here that has been a key motivation for me in building a Passive House. The indoor cold. During the winter, in both Sydney and Perth, I’ve never been as cold indoors in the my life! And I’ve lived in four different countries. In Adelaide a taxi driver who was originally from Afghanistan told me that the Australian cold, inside the houses, is like nothing he’d ever seen before. It gets into your bones, he said.
And I knew what he meant. When I moved here from the UK, I didn’t see that coming. But, it turns out that a home in Perth’s climate, over the course of a full year, needs five times as much heating input as cooling input. And “The evidence supports the claim that more Australians than Swedes die in cold temperatures“.
Is a German Passive House built the same as an Australian Passive House?
No. Achieving Passive House certification in Germany requires a VERY high spec building. Very high insulation, for example, and probably triple glazing. The Passive House Institute doesn’t mind how you BUILD your building, or what materials you use, or what it looks like. Their benchmarks are all about how your building PERFORMS.
To achieve Passive House certification, your house needs to deliver a specified level of comfort. Construction-wise, this is easier in Perth than in Munich.
A German and an Australian Passive House are equal in comfort, not construction
Building a Passive House in Australia is not about using German building methods. It’s about enjoying German levels of comfort. A Passive House, no matter where it is, is designed to provide an internal temperature of 20-25C (68-77F) for at least 90% of the time. All day long and all year long.
And equal in running costs
It must also deliver all that lovely comfort, including correcting those 10% of too hot or too cold days, with minimal active heating or cooling inputs. Year in and year out, for the lifetime of the building.
This is calculated in a spreadsheet (the ‘PHPP’) to calculate and forecast the building physics of your individual house design. Your home can only be certified as a Passsive House if it’s going to be both very comfortable and very energy efficient.
“My solar panels can achieve all that”
But can they though? I mean, that’s definitely part of my plan for my Passive House. In the middle of the day, while the sun is on my solar panels, if it’s a very hot or a cold day, I expect to be running my small cooling or heating system for a couple of hours. A key difference though, is that my house should then hang on to that extra coolness or heat pretty well, right around the clock, because of its good insulation, double glazing, airtightness, and (in my design) thermal mass (including the concrete floor slab).
Unfortunately standard Australian construction is very draughty. “For many of us, we are paying thousands of dollars a year to heat our homes, only for this heat to escape straight through gaps in the walls.” Brand new houses can allow 10-15 air changes per hour. Any heat or cooling you add to the air inside your home is likely to exit the building pretty fast. So unless you’ve also got an expensive battery, your solar panels aren’t going to be relieving your home’s evening heat in the summer, and even less so its evening cold in the winter.
“But you’re not allowed to open the windows in a Passive House”
Nope, this is another myth. I’m not even sure where this one comes from. Not only are you ALLOWED to open the windows of your Passive House, but the Passive House PHPP spreadsheet will actually give you CREDIT for a house design that allows good cross-ventilation. This is precisely so that if a hot summer’s day finally eases, you can open the windows to flush out some of that heat. (Although I’ve got my home automation sending me notifications when the external temperature drops below the internal temperature, and there have been nights lately where that hasn’t happened until many hours after my bedtime…)
Similarly the Passive House spreadsheet will give you credit for many other aspects of good home design, including orienting the building well, getting your window shading right, and myriad other adaptations that are relevant to your specific design, setting and climate. The more of all those things you can optimise, the more it lets you cut back on your insulation a bit, or your glazing specification, and still meet the standard. They’re not simple minded, those Passive House Institute peeps. They’re putting a lot of thought into all this.
Does it work?
There’s so much more to say about Passive House, and all the science behind it. But, to dive into every detail would take all week. For me, it feels like a great choice. I really can’t wait! Every Passive House I’ve walked into has been at an immaculately comfortable temperature, no matter what is happening outside, and every Passive House owner I’ve spoken to is just over the moon about how great their house is to live in. On top of the thermal comfort, they mention the quietness, lack of dust, lack of bugs, lack of condensation and mould, and so on and on.
Comfort is comfort, anywhere
So to sum up, the Passive House standard was developed in Germany, but building to this standard is actually easier in Australia than in Germany, precisely because we don’t have those cold cold winters. The reason that Passive House can be a relevant choice anywhere is because comfort and efficiency are universal. Thermal comfort inside our own homes is something that Australians deserve just as much as Germans.
Image by Jerzy Górecki from Pixabay