How do you renovate a home as a Passive House (or Passivehaus)?
Especially when that home is an early 1900s weatherboard cottage?
In this episode, I’m going to be sharing the experience of a homeowner who renovated their early 1900s weatherboard home into a Passive House. They’ve lived in it now for 3 years, and it’s located in inner Melbourne, about 10km from the CBD.
This project is a great opportunity to see how an old weatherboard home can be renovated into a Passive Home that is comfortable and saves thousands in running costs each year.
Cameron’s family home is known as Armadale Passivhaus. They open this home for Sustainable House Open Day each year, and Cameron also has a great website on all the nitty gritty details of the home and project (see the resources below for more information).
Circa 1910, this weatherboard home faces north-to-street. So, if you’ve listened to this podcast for a while, and heard the episodes I did back in Season 1 about orientation, you’ll know that north-to-street is a challenging orientation in the southern hemisphere.
This is because we like to put all our main living areas at the rear of the home, with indoor / outdoor connection to perhaps a deck or alfresco area … and lots of glazing to connect the two. And if the home is north-to-street, it means that the sun is moving around the front of the home, and not the rear.
This means, especially in a location like Melbourne, that the rear of your home can be cold, in shadow, and not getting the natural light you want into your main living areas.
The home also has a heritage overlay, which meant that extensive alteration to the facade wasn’t allowed, and there were two brick chimneys that had to be kept. Lots of homeowners would say at this point – “Forget Passivhaus … we’re putting this entire renovation in the too-hard basket!”
The Armadale House sits on a 430m2 block in inner Melbourne, Australia, and is located about 10 km from the CBD.
Cameron and his family had lived in two weatherboards home prior, and so their experience was always that leaky sieve experience you may be familiar with if you’ve ever lived in a weatherboard house. You can feel every breeze move through them. They’re hot in summer, cold in winter, and terrible performers thermally.
When they moved into the Armadale house, it was the same experience. They could see the sky, sunlight coming in below the door, and the windows would rattle with the slightest breeze. The chimneys meant they could see the sky, and rain would come down them whenever it rained.
It’s inspiring to see how this home was renovated 3 years ago, and how this family stayed committed to their desire to create a comfortable, sustainable home. There’s a huge amount of knowledge to gain from this project, and seeing how you can renovate your own Passive House.
As I explain in the podcast, the audio recording of my interview with Cameron did not go to plan!
So, listen to the episode as I share the highlights from my conversation with Cameron. And then keep scrolling to read the full transcript of our interview. Both will share key tips, strategies and knowledge to help you with your own project.
LISTEN TO THE EPISODE HERE:
In this episode, I ask Cameron …
- Can you please tell us about your home, the Armadale Passive House … who lives there, rough area of it, the block of land it’s situated on, how long have you lived there?
- It’s a weatherboard house and those are notoriously challenging in terms of keeping internal air temperatures stable and being energy efficient homes. What prompted you to create a Passive House in your renovation?
- What makes it a Passive House? How does it work, what is special about it, what differentiates it from a more traditional house
- Do you remember at the time if you were worried it would limit you in anyway or any compromises you’d have to make?
- Where do you see the big differences in living in a home like this (feelings, and tangible cost savings etc)?
- Your extension is in rammed earth – can you tell us about choosing this material and why you did because it’s such a contrast to the weatherboard
- Can you talk about your window selection, because in Australia, I know we LOVE our windows for all that indoor / outdoor connection!
- What specific advice would you give to those who are renovating and want to create a Passive House?
READ THE TRANSCRIPT HERE:
Amelia Lee: Well thanks, Cameron, so much for joining me today. It’s fantastic to have you here. And I’m really excited to talk to you about your home, because it’s actually not what most people would expect to tackle when doing a passive house. And I know that you’ve had a fantastic experience of living in your passive house. So can you tell us a little bit about your home? It’s called the Armadale Passive House. You know, who shares the home with you, whereabouts is it roughly located, the type of block of land that it’s on, and how long you lived in the home?
Cameron Munro: This is our family home, so it’s my wife and our nine-year-old. We bought the place about four years ago. It’s a weatherboard, sort of 1910 era building, and pretty much no insulation when we bought it, and needed a fairly thorough renovation, so there was a challenge in that. The block’s about 10 kilometres from the Melbourne CBD, so it’s pretty inner suburban suburb.
The block itself is about 430m2, so it’s not huge. And the home is now about 143m2. And as part of the renovation, we stripped it back to its bare-bones, and almost started again, but within the constraints of having a heritage overlay, and really trying to retain the architectural integrity of the building as it was.
The block itself is about 430m2, so it’s not huge. And the home is now about 143m2. And as part of the renovation, we stripped it back to its bare-bones, and almost started again, but within the constraints of having a heritage overlay, and really trying to retain the architectural integrity of the building as it was.
Amelia Lee: Because it’s a weatherboard house, isn’t it? And so, I know from experience they can be very difficult, because they’re not really designed for the thermal requirements. They can be leaking sieves when it comes to keeping the breezes out. And they can be really challenging just in terms of working with generally. And they’re not what you picture converting into an energy-efficient passive house. What prompted you to make that decision when you thought about renovating? Because I can imagine with the heritage overlay, and all the other sort of constraints that you had to deal with, the small lot and that type of thing, probably many other homeowners would’ve gone, “Oh, it’s all just too hard. I’m just going to do a standard renovation.” What made you want to do a passive house?
Cameron Munro: So, the previous two houses we’ve lived in were also weatherboards, so we have experienced very much of that leaky-sieve type of experience, which is never a pleasant one, particularly in a Melbourne Winter. And even, indeed, in the Summer for that matter. And in this place, when we bought it, we could see the sky, sunlight coming in below the door, and the windows would rattle every time you had the slightest breeze, and had two chimneys in the place you could see sky through, and rain would come down the chimney whenever it rained.
Cameron Munro: So, it had all of those detrimental aspects to it. That’s probably our motivation here really, was first and foremost the comfort. We were looking for a comfortable building for us to live in. And my wife is Swedish, and so we’re moving to Australia some 10 years ago, the first Winter she experienced here she described as the coldest Winter she’d ever been through.
Amelia Lee: Wow.
Cameron Munro: This is coming from a country where they have snow on the ground for five months of the year! And having lived in Sweden myself for 10 odd years before coming back to Melbourne, coming back to homes here was a real shock. Being brought up in Melbourne and then moving overseas, I never had experienced anything different, and I thought Australian homes were fine. But when I came back I thought, “No, there’s something seriously wrong here. This just doesn’t feel right anymore.”
So, it changed my baseline for what a comfortable home could be described as. And certainly in my wife’s case, she’d never experienced anything other than a building which remains thermally stable, irrespective of how cold or warm it is outside. And that doesn’t need a huge heating and cooling system constantly blasting a way to keep it warm or cool. So really, our motivation was trying to achieve a comfortable building, but not just do it in a way that perhaps we traditionally had done it in Australia, which was just stick on a great big heater or air conditioner. Trying to do it a bit more intelligently and thoughtfully.
So, it changed my baseline for what a comfortable home could be described as. And certainly in my wife’s case, she’d never experienced anything other than a building which remains thermally stable, irrespective of how cold or warm it is outside. And that doesn’t need a huge heating and cooling system constantly blasting a way to keep it warm or cool. So really, our motivation was trying to achieve a comfortable building, but not just do it in a way that perhaps we traditionally had done it in Australia, which was just stick on a great big heater or air conditioner. Trying to do it a bit more intelligently and thoughtfully.
Amelia Lee: I think that’s really interesting actually, because often our expectations are set by just what we’ve experienced previously, and what we believe is the norm, isn’t it? So, the fact that you do have that benefit of experiencing something different, in a more challenging and extreme climate, and seeing that there was a better way of doing it, is actually a really fantastic opportunity, isn’t it?
That’s not something a lot of people generally get, to sort of teach them that perhaps we can do it differently. It’s not just about, like you say, let’s install an air conditioning system, and let’s just pay for the privilege of hot and cold temperatures. Instead, let’s actually look at the building itself, and what can be done in the way the building is designed and built, to protect us from those elements.
And so, I think that’s a really interesting perspective, because Australian homes are pretty poor performers thermally, aren’t they? So when you do compare it to a lot of those European homes, they’re much better set up to protect the occupants from the weather, and the climate, and the extremes, aren’t they?
That’s not something a lot of people generally get, to sort of teach them that perhaps we can do it differently. It’s not just about, like you say, let’s install an air conditioning system, and let’s just pay for the privilege of hot and cold temperatures. Instead, let’s actually look at the building itself, and what can be done in the way the building is designed and built, to protect us from those elements.
And so, I think that’s a really interesting perspective, because Australian homes are pretty poor performers thermally, aren’t they? So when you do compare it to a lot of those European homes, they’re much better set up to protect the occupants from the weather, and the climate, and the extremes, aren’t they?
Cameron Munro: They are. And it would be an interesting thing in this passive house space, is that probably 80% of the people involved are either of European origins themselves, or have a partner, or have lived in Europe for a number of years. So my experience is by no means unique, and there seems to be a pretty common sort of a thing, where you have an Australian who goes over and lives in Europe for a few years, comes back and realises that there’s just something not quite right about the way we build here.
And I should point out also, it’s not simply about the air temperature in the building. So we can easily get our air temperatures in the building up to 20 – 25 degrees with a heater and an air conditioner. That’s not a particularly big challenge, as long as you’re prepared to chuck energy and money at the problem. It’s really the sense of comfort that we have though, is a factor both at the air temperature and the surface temperatures, on the walls and the windows, and the draughts that we’re getting through the windows and door cavities when it’s windy outside.
So, to achieve proper comfort, in a sense that you would define in a high-performing European home, is about more than just throwing heat and cooling at the problem. It’s about looking at the building fabric.
And I should point out also, it’s not simply about the air temperature in the building. So we can easily get our air temperatures in the building up to 20 – 25 degrees with a heater and an air conditioner. That’s not a particularly big challenge, as long as you’re prepared to chuck energy and money at the problem. It’s really the sense of comfort that we have though, is a factor both at the air temperature and the surface temperatures, on the walls and the windows, and the draughts that we’re getting through the windows and door cavities when it’s windy outside.
So, to achieve proper comfort, in a sense that you would define in a high-performing European home, is about more than just throwing heat and cooling at the problem. It’s about looking at the building fabric.
Amelia Lee: So, how do you describe passive house to people when you say, “Look, we did our renovation in a passive house, based on Passive House Principles?” How do you explain that to people?
Cameron Munro: It’s a challenge. I think the first thing I say, it’s about comfort. It’s about achieving a building environment that’s irrespective of what’s going on outside. Whether you be in far North Queensland in a super humid, hot climate, or in the highlands of Tasmania, it’s about saying the inside of that building is perfectly comfortable all the time. And it’s comfortable without having to throw energy at the problem to fix it.
It’s really as simple as that. And then the follow on from that of course, is you need a much smaller heating and cooling system than you otherwise would’ve done. And once you’ve spent all that emotional energy and financial energy in building the home, it stays very cheap to run forever after. And that is a pretty compelling sort of a pitch sometimes I find, to people who are haemorrhaging at their energy costs.
It’s really as simple as that. And then the follow on from that of course, is you need a much smaller heating and cooling system than you otherwise would’ve done. And once you’ve spent all that emotional energy and financial energy in building the home, it stays very cheap to run forever after. And that is a pretty compelling sort of a pitch sometimes I find, to people who are haemorrhaging at their energy costs.
Amelia Lee: Most definitely. And I think, in speaking to the other guests that we’ve been having on the podcast about passive house, it is thinking about that long term maintenance running costs of the home, when you’re thinking about the investment you’re making in the renovation, or build of it. And balancing the two against each other rather than treating them as isolated costs and expenses in your life. So, I think that it’s fantastic to see that sense of planning, and that it’s not just about the comfort, but it’s about those future savings that you can make in your energy bills as well.
So, what passive house features does the house actually have? Because given it is a weatherboard cottage with a heritage overlay, I imagine there are a fair few constraints in terms of what you could do with it. How did you incorporate passive house features, and what types of features does the home have?
So, what passive house features does the house actually have? Because given it is a weatherboard cottage with a heritage overlay, I imagine there are a fair few constraints in terms of what you could do with it. How did you incorporate passive house features, and what types of features does the home have?
Cameron Munro: One of the things that really appeals to me about passive house is that it’s a system. That you can’t just take one part of it and incorporate that without incorporating all of the parts. So passive house is fundamentally about super insulation. So insulation that’s much thicker than the Australian standard we require, but that is also installed properly. And that’s an absolutely critical factor, because in typical Australian building practise, we put an insulation bat in the wall, throw it in there, there’s gaps all around the sides, and we say that’s fine. Well, it’s not fine.
Cameron Munro: Heat has an innate tendency to find the easiest pathway through a construction, and it will just go around about, and you’ve lost most of the effectiveness of what you’ve just tried to do. So we use super-insulation. We do thermal bridging, which means we try to avoid any parts of the building, particularly the structure, so any of the timber framing, any steel in the construction particularly.
Cameron Munro: In short, we’ve got a continuous insulation layer across the building, so there’s no easy point for the heat to escape. I’m talking here particularly of a Melbourne client, but the same applies in reverse, in a really hot climate as well, if you’re trying to avoid the heat getting in.
Cameron Munro: And the next factor is super-insulated windows. So we have triple glazing all of our windows here. Windows are far and away the largest source of heat loss in a building, even an uninsulated building. So, you really have to invest a lot in the windows to really reduce your heat loss.
Cameron Munro: Another factor is airtightness. This is the aspect that tends to be missed in Australian building practise at the moment, where we have increasing awareness of insulation. Once you put insulation into the building, then an increasing proportion of your heat loss is going to be through air infiltration and ex-filtration through building fabric.
Cameron Munro: Australian buildings are notoriously leaky, and there’s really very weak standards within our building codes that requires any sort of attention to airtightness. And there’s no testing. So if I would go and buy a new home now, there’s no testing that’s performed on that building to demonstrate that it meets any sort of level of airtightness.
Cameron Munro: So what is really different about passive house is just how airtight the building has to be. And we’re talking in numerical terms it’s about 0.6 air changes per hour. So that means that the building, when it’s windy outside, will lose no more than 60 percent of the volume, the air volume of that building every hour. And that’s very tight compared to a standard Australian home, which is about 15 air changes an hour, for a new build. And for an old build, like this one was originally, up around 30 air changes per hour.
Amelia Lee: Wow.
Cameron Munro: So we’re talking about a reduction in the air infiltration of 0.6 over 30, so about a factor of 60. And the way to achieve that is not simply by caulking along the skirting boards, and trying to pay attention to putting seals around the windows and the doors, but rather running a membrane. Essentially you could think of it like cling wrap. All around the walls, and across the ceiling, down to the floor. Tape it. You can fix it with glue as well.
Cameron Munro: So you create a continuous airtight membrane across the building. And once you’ve done that, then you test the building. You pressure test it. You put a fan on the front door, and you essentially push air into the building, and suck air out of the building, and you test how airtight it is. And you can go in with that, before you put the plaster in, to make sure that that membrane truly is tight. And where necessary you can go over and tape, and fix any tiny little gaps that you’ve got there.
Cameron Munro: What that does, that airtightness does, is it stops the movement of that warm air that you’ve just warmed in your room, in your building to outside. But it also stops the movement of moisture into the wall construction.
Cameron Munro: This is another aspect that this is not really being paid much attention to in Australia, is the question of mould. And mould forms when we have moisture in the air, that goes from a warm climate, so in Melbourne that would be inside in the winter, heads through the wall, into the ceiling space. It cools as it moves through the air, and that water drops out, it forms water droplets in the wall construction, and then you get all his moisture forming. Which of course is not good for the structural integrity of the building, but moreover it’s not good for the health of the inhabitants, because it will encourage mould growth. So we need to stop the movement of that air across the construction, and that’s what the membrane helps us to achieve, as well as reducing our energy costs.
Amelia Lee: And we’ve been talking about this, it is that integrated system, isn’t it? It’s really, it has to all be done as a holistic comprehensive process and choice. And I love the fact that you can actually test the building before you start lining it, so that you can know with certainty that the house is performing as you anticipate it needs to to meet those standards. So, that’s a great piece of information for homeowners to understand, with that blower test, that it’s done at the point before plasterboard can go on, so that you can really ensure that you have sealed the home from those air leaks effectively.
Cameron Munro: And that’s absolutely critical. And it comes back to this question, of cost over the lifecycle of the building too. Doing these sorts of things when you’re building, and you’re so financially constrained, and looking to save cost is often challenging, and it’s tempting to say, “Well, no, I’ll compromise on the insulation, or I’ll only go single glazing instead of double glazing. I can’t afford it right now.” The problem is of course retrofitting these things in five or 10 years. It’s very much more difficult. And that’s particularly true of aspects like the airtightness. Once the plasterboard’s going on, there’s very little you can do to rectify any airtightness issues.
Cameron Munro: And perhaps the other thing to suggest as well is that it is fairly easy in most Australian capitals now to find a company that will pressure test your home. So, they’ll come out for a couple of hours, put this fan on the front door, and pressurise the building. And it’s one of those really insightful, jaw-dropping moments the first time you do this. Our home was the first one I’d ever experienced. When you pressurise it, and you just see how leaky it is. And that, I think, is one of those really transformational sorts of things, that just changes the way in which we think about building.
Amelia Lee: Because you suddenly realise, don’t you, that you’re paying for all of this heating and cooling that’s actually just disappearing outside.
Cameron Munro: Exactly. And moreover, you feel it indirectly. Even if you’ve got a nice new home, with a great big heating system in the winter, it’s blowing outside. When you go and stand by the window, you might feel a sense of draught, chill, and that’ll be a combination both of the air moving in through around the window sill, and also the surface temperature of those windows, which will be pretty close to the outside air temperatures. And we just feel that as a sense of chill, or cold. Whereas a passive house, a building like the one I’m in right now, just never has that sense. I can walk around any room in this building and the temperature is stable, always.
Amelia Lee: Just amazing. You sound incredibly knowledgeable about this, and the process that you’ve gone through. How did you embark on this, in terms of thinking, “Okay, we’re going to do this. What do I need to learn? What team do I need to find? How do I make decisions about budgets and materials?” And those types of things. Can you remember back to how you sort of kicked off that process for yourself?
Cameron Munro: So for us it was very much … it’s a learning experience. So 10 years ago we did a relatively small renovation on a weatherboard home we’d owned previously, where we swapped out the single glazed windows for double glazed, and pumped a foam insulation into the wall cavity. But it didn’t require a major renovation. That was our first sort of stepping stone along this path, and gave us a bit of experience.
Cameron Munro: When we looked at buying this home, we knew it needed an extensive renovation, so that was the opportunity then to do it properly, as it were. And really, my initial experience with Passive House was an internet search. And at that time, going back three or four years in Melbourne, there weren’t that many passive house designers.
Camerons Munro: So there’s an accreditation process for people who are experienced in this. There simply weren’t that many out there. There certainly were very few builders with any experience of it, very few suppliers of windows, and other systems that you would need for these sorts of homes.
Camerons Munro: So there’s an accreditation process for people who are experienced in this. There simply weren’t that many out there. There certainly were very few builders with any experience of it, very few suppliers of windows, and other systems that you would need for these sorts of homes.
Cameron Munro: So a lot of it was learned through the internet, buying some books. Many of which are out of the UK, or mainland Europe, so were difficult to translate to the Australian building experience. So at that time, it was quite challenging.
Cameron Munro: Now, it’s quite different now, in the two or three years since we’ve moved into our place. There’s now a lot of passive house certified designers in Australia. There is an increasing pool of builders who have experience building these sorts of dwellings. And there’s more and more suppliers of equipment, many of which for example will import windows from Europe. Or there is even in local manufacturers of windows now that are building to the highest European performance standards. So that’s helped.
Cameron Munro: Combined with that, I suppose, my background experience as a Mechanical Engineer. So I have a numerical bent, and passive house is very much about the numbers and the physics. It’s not about touchy-feely stuff, it’s about physics, the reality of how heat moves across a building. And so I had some, I suppose, grasp of those sorts of concepts.
Amelia Lee: I can imagine that your background and that sort of scientific understanding of things would definitely have assisted. Do you remember being worried about, I suppose, at limiting your lifestyle in the home, or the modifications you might have to make to your behaviour of how you lived, and your use of things in the home. Do you remember being worried about those kinds of constraints at all?
Cameron Munro: No, not in the slightest. And that would never fly, of course, if we had to make substantial compromises to the way in which we lived, or be prepared to live within a house that was, for example, 12 degrees in the Winter or something. I just can’t see that that would ever reach the mass market. And we weren’t prepared to make those sorts of compromises either. We had all sorts of other requirements on our home, on our family home just as everybody else does. And so fundamentally we didn’t have to make huge fundamental compromises.
Cameron Munro: Perhaps if there were any compromises, they were both to the size of the building itself. It’s not a huge home, but it’s perfectly reasonable size for us.
Cameron Munro: And secondly, perhaps to the window orientation. The windows are, by far and away, the single most expensive item in the building. And so if you want to have lots and lots of windows, then there’s lots and lots of cost. And you have to be really careful about the orientation of those windows. So we have a north facing frontage of our building, so the garden is to the south. So we didn’t want a full wall of glass facing south. If we were to do that, that would lose an awful lot of heat. But we still wanted the connection to the garden at the back. And so we just compromised in a sense, by having some slot windows that provided vistas out to the backyard, without creating huge expanses of glass. This is partly a cost-saving measure and partly an initiative to ensure that we don’t have huge heat losses across the glass.
Cameron Munro: And that perhaps is a philosophical difference, who, in many Australian climates now we seem to be fixated on having huge walls of glass everywhere. You can still do that, but you’d have to be prepared to pay for that privilege. And we didn’t feel it was necessary for our lifestyle to do that. In terms of the operation, there’s nothing whatsoever that’s different from the other building.
Cameron Munro: And this question keeps coming up when we have open days here, is that, if I come back to this airtightness thing is, once you build a really airtight building, then all of a sudden you’ve got a new problem you’ve introduced, because you not getting that natural flow of fresh air into the home anymore, like you do in your normal leaky building.
Cameron Munro: And so you need to introduce fresh air, and we do that through mechanical ventilation system. So there’s basically, in our laundry, there’s a small cupboard with a box and it, and then a bunch of ducts that run into each of the rooms in the home, and they deliver fresh air into the house. And they also feed off extract ducts that take on the wet spaces, the bathrooms, and the kitchen, and they take that warm stale air back to this box in the laundry. They take the heat out of that air, transfer it to incoming cold fresh air from outside, and deliver it into living spaces.
Cameron Munro: So we have this constant regular flow of comfortably temperature air into the living spaces, to provide an indoor air quality that’s far superior to anything that we would’ve got in a standard Australian home. But moreover, it’s being delivered at a comfortable temperature all the time as well.
Cameron Munro: And so, people often ask about that, you know, can we open the windows? What happens when we open the doors? What happens when we go out on holiday?
Cameron Munro: And the answer is you do absolutely nothing. That box sits there in the laundry, it runs at about 30 watts, which is running about half of a standard halogen downlight. It just ticks away, it consumes almost no power. We have to do nothing to it, except every six months I take the filters off and vacuum them, and every year I swap them over for new filters.
Cameron Munro: But there’s nothing whatsoever that we need to do differently in the way we operate the house. And if it’s a nice comfortable temperature outside, we can choose to open windows and doors, just like anybody else could. So really, there’s no difference whatsoever.
Amelia Lee: That’s great. We’ve joked in other episodes about the fact that there’s an alarm in head office of passive house that goes off when somebody opens the window in a passive house! There’s this misconception about the fact that if you live in a passive house you can never open a window. So, it’s fantastic that you brought that up. You do actually have … and I’m going to share a link to it in the resources for this … you’ve put together a fantastic website, which has got some really great information about your home, and the process that you went through, and about some of the numbers and the science behind it.
Amelia Lee: And also, you go into some detail about the windows themselves, which I think is really great information for anybody who’s thinking about embarking on a passive house journey. Because we’re in Australia we do have this love of indoor outdoor connections, lots of big areas of glazing. And we often do that with very little regard to the orientation. We kind of figure out we’re going to have all these views, and this indoor outdoor connection, then we think about the orientation as a secondary thing. Rather than thinking about it first, before the window design, which is obviously what you’ve done in your home.
Amelia Lee: In terms of that window selection, and the frame type, and those types of things, you mentioned that you’ve gone for triple glazing, which I know has been the solution for the Owl Woods Passive House as well, which we’ve spoken about earlier in the season. Can you talk a little bit about the windows, and how important they are in protecting the home overall?
Cameron Munro: So ‘vitally important’ is the short answer. So a typical Australian home, the windows will lose in the order of maybe a third of the heat across the building. And that actually, that proportionately remains true even in our home, even though we’ve gone for triple glazing. But the difference is that the total heat loss across the building is about reduced by well over 90 percent, close to 95 percent compared to the building that was here previously.
Amelia Lee: Wow.
Cameron Munro: So we’re not talking about an incremental small improvement in heat transfer, we’re talking an order of magnitude or more. It’s a huge, huge difference. But windows are absolutely fundamental, both for the heat transfer and for the air infiltration. And you simply cannot consider single glazing for a passive house, or any sort of energy-efficient building, because of the heat transfer across glass. It’s just never going to to be efficient.
Cameron Munro: In most Australian climates, if you’ve got a great orientation on the building, and you’ve thought carefully about where the glass should be, so predominantly north facing with eaves to ensure you don’t get summer over-heating, then double glazing is probably adequate. But then there’s all sorts of differences, even within double glazing. So we talk of U values, which is the rate of heat transfer across glass. And the U value of typical double glazing is in the order of about 2.5. But that of the most efficient double glazing is close to about 1.2. And the lower number is better, so 1.2 divided by 2.5, is a reduction of about a factor of two. So the most efficient double glazing will have about half the heat transfer of the least efficient double glazing. So, ‘double glazing ain’t double glazing’!
Amelia Lee: Yes!
Cameron Munro: And there’s also factors in terms of what you put in the glass, that you can just have air in it, or in our case you can then get Argon. You can put all sorts of films on the glass, which you don’t see, but they’re chemical treatments on the glass to reduce the heat transfer across. And then even the spacer around the glass. With double or triple glazing, you’ll have a little inch spacer around the glass, just to make sure that those panes of glass stay separated. And that typically is aluminium. And aluminium is a great transferer of heat.
Cameron Munro: But to get anything other than aluminium in Australia was exceptionally difficult. In Europe it standard to have a polymer or plastic inner space, but it’s very difficult to get them in Australia. And then the final factor is the window frames themselves. So, the standard cheapest window frames we get in Australia will often be aluminium extrusions. They won’t be thermally broken, and again aluminium gain is a fantastic transferer of heat.
Cameron Munro: So you can buy the fanciest glazed, double or triple glazed panes of glass you can buy, but if you put them in an aluminium frame, then you’ve pretty much wasted your time, because all that heat’s still going to transfer across the aluminium frame. So all of the components have to be considered together, and the best frames generally will either be a UPVC, a plastic, or a timber frame. There are also thermally broken aluminium frames, that can be reasonably acceptable as well. So again, there’s no real restriction here on design.
Cameron Munro: There’s all sorts of wacky designs of passive house out there. The wackier you go, the harder you have to work to try and make sure you hit the image targets.
Amelia Lee: And your extension is in Rammed Earth as well. I love that as a material, I think it’s fantastic, a fantastic choice. But it’s not a customary choice for an extension to a weatherboard home. Could you tell us about choosing that material, and how you went about making that decision, and you know, navigating the approval process, and all of those types of things?
Cameron Munro: So we love rammed earth because of the aesthetic. It’s just got a great life to it, that plasterboard just doesn’t have. And thermally it can be quite good, because it can act as a thermal battery, and store the energy, the heat when it’s warm, and release it when it’s cool. But really the big trick is to make sure that thermal battery stays entirely within the thermal envelope. And that means insulating, and our case externally, and also at the base, at the footings, to make sure that the heat that we’re storing in the rammed earth doesn’t get transmitted to the ground and dissipate away, or else through the wall into the outside.
Cameron Munro: So although it’s 300mm thick, and it looks massive, it’s a terrible insulator. So as a thermal battery, it stores heat, and it conducts heat. Inherently, a thermal store must also be a good conductor of heat. So you cannot just instal something like rammed earth, and not have it insulated. It’s got to be wrapped entirely to keep it within the building fabric, and that’s what we’ve done here.
Cameron Munro: So it’s exposed internally in our living room. And we can sit there, and frankly it looks much more attractive than the TV. And it creates a sense of life and character to the room. And it’s also a great acoustic thing too, because no noise transfers across 300mm of dirt.
Cameron Munro: And the other factor there is the embodied energy of it. It is 90% there, which will disperse. We took a 10% cement mix and it, so it has very low embodied energy compared to, say, concrete, even compared to bricks.
Amelia Lee: Fantastic. I’s a gorgeous natural finish that does add a lot of richness. It’s as you say, it’s got a lot of character, and it’s a lovely aesthetic. It’s fantastic that you’ve been able to incorporate it into the renovation of the home, and that you’ve seen such benefits from it as well.
Amelia Lee: So now, I suppose the last thing I wanted to ask you is I can hear people saying, “Look, it’s alright for him, he’s a mechanical engineer, he gets this stuff,” and it’s clear that you have understood the science of it, and that’s armed you well as you’ve navigated to resolving this for your home.
Amelia Lee: What would be your tips to homeowners who are thinking about passive house, and perhaps aren’t as scientifically minded, or they have been listening to the information they’ve been sharing and just thinking it’s all a little bit overwhelming, and sounds a little bit difficult? What would be your recommendations to them in going about this, and really staying committed to it along the journey?
Cameron Munro: I think I would suggest two steps. Firstly, convince yourself that this is indeed worthwhile. In a number of Australian states now there are people like myself, who’ve built passive houses or close to it, who are keen and willing to talk to others. Once you get deeply engrossed in this, you become something of an advocate for it. There’s also plenty of books out there, of different levels, both sort of beginner books if you will, that don’t have any of the technical detail, and just describe the principles and the benefits that passive houses bring, through the very technical books as well. So there’s that combination.
Cameron Munro: But secondly, the critical thing I think, if you’re not technically engrossed in the subject, is to get a passive house designer on board early in the project. So in some cases, the passive house designer will also be an architect or a building designer, that you may be interested in using. Otherwise, in other cases it might be a passive house designer might be separate from the architect, but they work collaboratively, where the architect does the building form, and then the passive house designer does the thermal modelling and the design detailing that’s required to achieve the passive house standard, and can assist with some of those nitty-gritty details that are so critical about things like airtightness.
Amelia Lee: Fantastic. And you’ve got some really great information on the website you’ve created, which goes through those cost savings. You also talk about a hybrid car that you guys have, and how the offsets in that have compensated for some other upfront costs. So, I can see this holistic approach to the way you thought about creating this home, and your lifestyle overall has fundamentally really shaped that approach to the budget, and those types of things. How long have you been in the home now?
Cameron Munro: Oh, we’ve been in just under three years.
Amelia Lee: Okay. And so seeing the benefits of that, the savings and those types of things, the decisions you had to make about your budget upfront, you mentioned that you, you know, the size of the home was obviously managed by your budget, to be able to then afford some of those passive house features, like the triple glazed windows and those types of things. Are you seeing that the savings are well and truly compensating for those upfront costs that you had in the actual renovation?
Cameron Munro: They are. I mean again, this is not really a financial matter, it’s one of comfort, and how much do I value that, in the same way that some may value a Caesarstone kitchen bench top differently, you know, what’s the payback? What’s the energy savings on something like that? So our costs, I think, over a 12 month period are in the order of something like $450.00. We have no gas, that was removed, so there’s no gas connection at the building. We have solar PV on the roof. We export far more electricity than we consume.
Cameron Munro: The $450 then covers all of our heating for the space heating and cooling for the home, which is of course small, since it’s almost a passive house. The heating of the hot water, lighting, computers, and all of the usual electrical appliances in the building. Plus the car, which drives about, I think we got it just over 10,000 kilometres of all electric driving last year, all incorporated within that $450. So the fuel cost saving alone makes it worthwhile.
Amelia Lee: That’s extraordinary.
Cameron Munro: And you’re removing a lot of your fixed connection costs, because if we had a gas connection here, simply to run a gas hob, or a hot water system, we’d be up for about a $400 – $500 just for that connection alone, let alone the actual consumption of the gas.
Amelia Lee: Cameron, I can’t thank you enough for how generous you’ve been, and the information you’ve shared about your home, and creating your renovation, and what it’s like to live in. Now I know that the UA community’s going to find it really helpful to see the inside of somebody who’s had a couple of years living in a home like this, and really talking about the comfort levels, and how different it is … not only from a cost-benefit, but particularly from a comfort level. It just sounds like the ideal scenario that so many of us are seeking when we create our future family homes. So, thank you so much for your time, and I’ll be popping links to the resources. There’s lots that you can find online about the Armadale passive house, which is great. Do you continue to open it on the sustainable house stays?
Cameron Munro: I do indeed. I’ll be here next year.
Amelia Lee: Brilliant. All right, so you can go and also have a look through the home and see for yourself. So thanks so much for your time, Cameron, I really appreciate it.
Cameron Munro: My pleasure. Thank you, Amelia.
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RESOURCES MENTIONED IN THIS PODCAST:
Cameron’s own website about the home and its renovation >>>> http://cdmresearch.com.au/SHD/index.html
Sustainable House Open Day listing for Armadale House >>> https://sustainablehouseday.com/house/armadale-passivhaus/
With over 30 years industry experience, Amelia Lee founded Undercover Architect in 2014 as an award-winning online resource to help and teach you how to get it right when designing, building or renovating your home. You are the key to unlocking what’s possible for your home. Undercover Architect is your secret ally
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