Episode 02: What is a high performance house?
In the last episode, we spoke about our approach to designing efficient homes and mentioned the term hybrid home. So, we decided to elaborate a bit on what that means to us, and how these high performance homes are different to conventional builds as well as passive houses.
It is a brief talk, but we managed to touch on what high performance means to us, why it is so important and why we believe this is the way to go in the future.
Anthony, what does hybrid house mean to you?
Hybrid house is something we mentioned in our last chat and I suppose in industry terms at the moment, the closest thing you can relate it to is a high performance home. Let’s look at this as a spectrum. So, you’ve got a code build, which is meeting the minimum compliance in our national construction code. I imagine that’s where the bulk of housing stock being constructed is at.
And then we have the other end of the spectrum: A certified passive house, which is still a voluntary standard here in Australia. That’s giving us a guaranteed performance.
What we are proposing is not a certified passive home, but a home that sits just below that on the spectrum. The major reason for that is a lower budget and realistic built cost and expectations of clients.
So, that’s what a hybrid house is, it sits there with the same performance outcomes as a certified passive home. It is not fully there, but also a lot cheaper. It’s very much climate designed, and it basically provides all the fundamentals of a home: A comfortable home to be in, a home that is healthy, a home that doesn’t cost a great deal to heat and cool, and a home that is durable for not just 10, 20 or 30 years, but add maybe another 0 onto that. Let’s push it to 100, 200 years. That’s a big part of what the hybrid home is.
If we dive a little bit more into the details of the actual design, what are the differences to a conventional build and to a certified passive house, as well?
I’ll start with the certified passive house, because that’s probably where it’s most aligned to. It follows all the same principles, so we want airtightness and we want to increase the thermal envelope, and we also incorporate HRV systems.
That’s a ventilation system, right?
Yes, that’s right. HRV stands for heat recovery ventilation system. In winter, when it’s nice and toasty inside, the HRV is bringing fresh filtered air from the outside inside the home, running it through an exchanger to warm that fresh cool air up a little bit and then bring it inside the home and supply fresh air to all the rooms inside the home. It’s also exhausting all stale air from bathrooms, laundries, and kitchens. It’s basically controlling the internal environment when you don’t have your windows open. Your home needs to be ventilated, and whether you do that through opening the windows or the HRV system is up to you.
Gotcha. What other similarities are there to certified passive homes?
We are also looking at a thermal bridge free or thermal bridge reduced construction, so just trying to tweak a few standard construction details to reduce thermal bridging for hybrid homes.
Compared to a code build though, it’s a bit different. Although our intention is to have standard construction practices and standard materials, it still performs at a totally different level.
For a code build, for example, even in our climate zone here in Victoria, you don’t need to have any wrap on your roof at all. You don’t need to tape your joints on the outside of your wrap on the walls, you can leave those freely open. And airtightness is not considered whatsoever.
In fact, a builder reached out to us not long ago and mentioned just how many ceilings he had been replacing up in Mildura, just because they don’t put wrap on their roofs. That means that water is freely coming in and sitting on top of the plaster sheets. After a couple years of that consistently happening, those ceilings collapse, so he’s been doing quite a few of those. So, construction to the national building code, might be lacking in that. There’s a multitude of things. I could go on and on and on with the code build.
But what a high performance home is doing is first and foremost, responding to the climate, whereas code build really doesn’t or only very minimal. And it considers the health and wellbeing of occupants.
Except for certain reasons of fire, the code doesn’t consider internal air quality at all. They are probably the major things. And of course, comfort. Although there are some minimum requirements for insulation values in the national construction code, again, they are probably lacking in most climates.
That definitely needs to be improved on, but the big pushback there is the condensation risk – and that’s where our HRV system really picks up that short falling. It’s able to pick up moisture on the internal environment and disperse it outside and control that.
What’s really surprising is that if you have a conventional build, it is built to a minimum 6 star energy rating at the moment. That is assessed by a professional, a so-called thermal assessor, during the design phase of the house. So, basically, you design a house, give it to an assessor, and they come back with a star rating.
To my surprise, during the actual building process, that energy efficiency is not assessed anymore. This is something you’re willing to voluntarily change. You put yourself on the line and test your designs, to see if those 9 star energy ratings that your plans are getting, are actually performing to that in real life.
Absolutely. So firstly, you are right. The current NAThers assessment is purely theoretical. There is no inspection during the construction to ensure that what has been assessed on paper, is actually being built.
But that doesn’t mean that you can’t voluntarily test your home and make sure it is performing to the standard. We do that. We put our hand up to test our homes, our designs, as per what we are designing.
We have our own blower door system and we test for airtightness in a home and ensure it is where it needs to be. We also inspect insulation installation and make sure it’s all being done appropriately. Especially, you know, anything we can do to improve the thermal bridging aspect. And we can also use a thermal camera as well after plaster insulation, to assist with that.
That’s something that I want to put out there, and encourage more people to do this. For a very small fee, you can have someone come out there and perform these tests to ensure a home is performing as it should be.
I mean, if you buy a vehicle and discover that part of the engine or maybe the steering wheel or other parts are missing once you have driven home, you would probably take it back to the dealership and say, hey, I’ve paid full price for this, where are the other components of the car? And that’s how we look at it as well with a house. You’ve had this assessment done, but you don’t actually know if it’s performing to that assessment, even though there are ways to test and make sure it is.
So, I encourage everyone to get out there and make contact with anyone who can offer these testing services, and have a chat to your builder and see if they’re willing to incorporate it into the build. It’s advisable to maybe even include that in the contract early on, to make sure you have allowance for that in there, especially around blower door testing. There is a solution in the national construction code that you can extract and maybe incorporate into your contract with your builder. It’s only at 10 air changes per hour at 50 pascal, but it’s something to start with.
It’s good reassurance for you as a designer as well, to see that what you’ve come up with on paper is actually working. So, it’s good for you, but at the end of the day, also the clients, the people who are building this house. They are not going in blindly, assuming that it’s performing to a certain standard. They actually know. They have the proof that this house is going to be healthy, it’s going to be comfortable, and it’s going to be efficient for them.
Absolutely. It’s the only way that we can start to make assurances. If we wait for regulation change, it’s going to be years, I think, before we see this being mandatory. So, why don’t we just voluntarily do this?
We want to see regulations change, we want to see the building code be assessed, but until that is done – and we all know politics can take time – we’re just going to make our own rules. Prove our own work and make sure that our clients are getting the best performance home they can.
Absolutely. Why wait? We have the power to do this, if we all come together and start to push forward. Why wait for regulatory change?