Build Science Expert - Windows and Insulation Part 2
When it comes to building or renovating a home, insulation is one of those topics that seems simple on the surface, but quickly gets complicated. That’s why we brought in Cameron Munro from Passive Analytics to help us break down how insulation really works. In part two of this conversation we pivot the topic to focus on insulation used in walls and roof spaces.
The Science: Conduction, Convection, and Radiation
Cam started by reminding us that insulation isn’t just about stuffing something fluffy into your walls. The science behind it is all about stopping heat transfer, which happens in three ways: conduction, convection, and radiation. Most of the insulation we use in homes—like glass wool, rock wool, or polyester—works by reducing conduction. These materials are spun into fibres, creating lots of tiny air gaps that slow down the movement of heat.
Why Density and Air Gaps Matter
One of Cam’s big points was that not all insulation is created equal, even if the R-value (the measure of resistance to heat flow) is the same. The density of the insulation and the size of the air gaps inside it make a huge difference. Denser insulation with more, smaller air gaps generally performs better. For example, wall insulation is usually denser than ceiling insulation to prevent it from slumping over time.
Wall vs. Ceiling Insulation: Not the Same Thing
We often see people using the same insulation in walls and ceilings, but Cam explained why that’s not ideal. Wall insulation needs to be denser to support itself vertically, while ceiling insulation can be lighter and fluffier. If wall insulation slumps, it leaves gaps at the top, creating “cold spots” that can lead to condensation and even mould.
Installation Quality: The Hidden Factor
Even the best insulation won’t perform if it’s not installed properly. Cam stressed that small gaps or areas of “non-coverage” can dramatically reduce the effectiveness of your insulation. Just 1% of missed coverage can cut performance by 10%, and 5-10% gaps (which are common around power points, pipes, and windows) can halve your wall’s R-value. That’s why attention to detail during installation is critical.
Moisture Matters
Another key takeaway: insulation and moisture don’t mix well. Different materials handle moisture differently, and you want insulation that’s hydrophobic (repels water) rather than hydroscopic (absorbs water). Cam pointed out that in climates where air conditioning is used, moisture can move through your walls and floors, so it’s important to choose materials and assemblies that can dry out if they get wet.
There’s No One-Size-Fits-All Solution
If there’s one thing Cam hammered home, it’s that there’s no universal answer for insulation. The best approach depends on your climate, the design of your house, and how you use it. For example, in some climates, an uninsulated slab can actually help keep your house cool by acting as a heat sink. In others, you need to insulate everything to keep the heat in.
The Passive House Perspective
For those who want to take the guesswork out, Cam recommends looking into certified Passive House construction. The rigorous quality checks and modelling required for certification help manage the risks and ensure your home performs as expected.
After talking with Cam, we’re more convinced than ever that insulation is about more than just picking a product off the shelf. It’s about understanding how heat and moisture move through your home, choosing the right materials for your climate and design, and making sure everything is installed with care. If you want a healthy, comfortable, and energy-efficient home, don’t cut corners on insulation—or on the expertise you bring in to get it right.
LINKS:
Connect with us on Instagram: @themindfulbuilderpod
Connect with Hamish:
Instagram: @sanctumhomes
Website: www.yoursanctum.com.au/
Connect with Matt:
Instagram: @carlandconstructions
Website: www.carlandconstructions.com/
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[00:00:00] Cam: when we think of isolation, that's what we usually thinking of the, the glass wool. Yeah. Whacking our walls and our roots. We've reduced conduction because we've taken a bunch of velas and spun it and separated those fibers. but although there's gonna be fibers running from the warmed coal side, they're very thin.
[00:00:15] Hamish: And this is the same as Rockwall too, or a, a polyester glass plate. It's all the same from, the
[00:00:19] Cam: mechanism is identical. Yeah. All you're trying to do is take a cheapest chips material that you can spin into a wall. Our wool and jumpers, you know, our t-shirts, like everything operates in the same way. All of these fibrous materials is, we're just trying to create as many small way gaps as we can for as little dollars as we can.
[00:00:36] Hamish: So why haven't they then been able to pub like an r long gas into the insulation and to improve the value of the insulation?
[00:00:42] Cam: Well, in Syria, I guess you could do something if you then covered it on, say, needs to be closed. Yeah. Yeah. It has to be. We know what building side are like, you know, someone's gonna punch hole on it.
[00:00:51] I mean, this is, this is the, if we have a concern with, you know, with the extreme end, we now have these vacuum in burns, which are, you know, and the [00:01:00] extraordinarily good thermal performance. But on a building side, you just need to be careful because all you need to do is punch a screwdriver through that and it's going from super performance to no performance.
[00:01:11] So let's talk about space. Yeah. Okay. Right. This is what really gets the BMI bonnet going as every product manufacturer says invented by nasa, all of them say this and they're usually flogging a foil faced material and they're talking about in, and they are absolutely sort of rye when the, the space industry uses foils all the time.
[00:01:36] So you think of your classic satellite or spacecraft, you know how it's got that it looks like trapped in tinfoil. What's going on there? That is to reflect the radiant energy from the sun, because if you are in space, you've got the suns of rays hitting your spacecraft. How do you call it now? You can't call it by conduction because you've got space of vacuum around you.
[00:01:58] You've got nothing to conduct. [00:02:00] Two, you can't convec the heater away. Because you've got no air, so you've only got one way in which can, you can cool your spacecraft radiation and that's why you have the, the team face whatever materials the way it is.
[00:02:14] Hamish: Um, just, just on the, on the NASA stuff, um, and I think it's 3M have invented this really thin kind of wrap, which has an a value of like R four or something.
[00:02:26] Have you heard of this stuff? Like it's really thin. How, I don't know how la I don't dunno how it's not the subtle brake strips for steel frames. I've got brake strip strips. I mean, they might have to, you know, find some kind of show note to put it. It's all suited you, but do you want, it's probably a good point to touch on because it, do you wanna talk about the lambda value and then how then the thickness of installation and transcribes into.
[00:02:49] Performance.
[00:02:49] Cam: So it, the lader is the, the thermal will comeback ticket. It's a material property that's, uh, pointing me on the stand here. That it's a car fundamental character stick the material
[00:02:59] Hamish: that's from, [00:03:00] you're seeing this piece of hair, everything that we see might, has some form of lambed owner,
[00:03:04] Cam: a lamb.
[00:03:05] Yeah. Yeah. And so for, uh, you know, give some rough numbers. You have standard glass wall insulation. Bat is about 0.04 watts, ber meter, kelvin, a low value, lower values are better, less conduction. Then you go through just things like pine timber, softwood timbers. They're about 0.13. Hardwoods are a bit denser and therefore have more conductivity.
[00:03:26] There are 0.18, aluminum is several thousand, and steel is about 50. The, you think of it as risk ratio. You know, 0.04 is my best case. My, my glass full bat. If I just build a ball straight outta Tinder, say CLT. Yeah. Then it's about 0.13. So all that tells me straight off the bat is if I wanna get the same ave or thermal resistance out of a wall and I make, let's say it's a hundred mil of um, glass wall, then it's got a certain if to get the same out of ACL T.[00:04:00]
[00:04:00] Well, it's gonna to be three times a stick because the lamb, the thermal conductivity is three times higher than that of the glass hole. And then I'm gonna build it. That will add of solid steel 50 50 to divided by coin oh four is some we need to calculator for, but you're gonna have to build that wall 10 meters thick.
[00:04:20] You get the same thermal resistances at a hundred again blaster.
[00:04:23] Hamish: Yep. Yeah. Right. So, so there's a, there's a really good argument there for not building your hundred steel, hold on. You can build out steel and I'm one of the biggest people who have said steel sucks for framing. But if you are then to NCI externally.
[00:04:39] Could it be possible?
[00:04:39] Cam: Absolutely. Yeah. As long as you've got a continuous layer of it into the, you're essentially separating a structural layer, the steel fraying from your insulation layer, which, which which is typically not done, which is typically not done in Australia, your actors, but is done internationally.
[00:04:54] Yeah. And then you just, it gets, you know, in principle you go, well that's easy enough, I'll do that. But then you've gotta [00:05:00] remember, you've gotta put the windows in the insulation plane, don this wine.
[00:05:04] Matt: Yeah.
[00:05:04] Cam: And what are you gonna do at your slab junctions? And you, you've got, you know, the details might come back to bite
[00:05:11] Hamish: you.
[00:05:11] Yeah, yeah. And the aesthetics that, all that kind of stuff, like the finish. So you, you touched on wing washing before because, um, and I know everyone uses an analogy of the jumper and the Gore-Tex jack and all that kind of stuff, but, um, and this is relevant again to a project that you and I are also working on together and.
[00:05:33] I, it is. I guess the point I'm trying to get at with this question is that not all the insulation is made equal because some perform differently than others. Even though they may have the same R value, they depend. Yeah, exactly.
[00:05:47] Cam: So when you look at the, the data sheet for a glass wall product, you'll get different, like a level of thermal conductivity is reported, you know, I use 0.04 as an example, but it will vary from anything.
[00:05:58] Then about [00:06:00] 0.033 up to about 0.05. And so the, at the lower end, the better. So lower values being better that 0.03, three range is, it tends to be a higher density glass wool. So what they're doing there is they're spinning little glass full and they try to create in the same thickness, more air gaps. If I can have to pick a number, a hundred air gaps in that 90 mil thick bat versus 50, then more else being equal, I would expect that to have that.
[00:06:30] Hamish: So more smaller air gaps are bigger, better than. Less bigger ones. Correct.
[00:06:35] Cam: Okay. Correct.
[00:06:36] Hamish: And density is also bit the sound though. I think this is the other thing that so many people that are like, oh, we put our four between our sun floor and our first story, that's like, well we shouldn't be looking at insulation there.
[00:06:47] It's useful but for sound, not for,
[00:06:50] Cam: and so gives some acoustic dampier as well. Absolutely. Um, but the difference in those glass wall products, and this is the same between a wall, a wall glass wall [00:07:00] bat, and a ceiling glass wall bat. If you look at your compare your data sheets is the wall glass. Wall bat tends to be denser because they're trying to stop the slumping in the mall.
[00:07:10] And so the thermal conductivity flanders tend to be lower, so they'll tend to be anywhere between 0.033 and 0.04, which sort of rule the thumb. Whereas when you look at your glass wool ceiling bats, they're much lighter and fluffier. They're lower density. So your wall bats are sort of usually in the 20 to 28 kilogram per cubic meter density range, whereas your ceiling bats are closer to a half.
[00:07:34] That 20, about 10 kilograms per cubic meter and therefore the thermal conductivity is higher. They've got a more larger air gaps.
[00:07:46] Hamish: So is that so in a ceiling? So if I was to say, hypothetically, if I put two R four HD bats, that would be better than one R eight bat?
[00:07:58] Cam: No,
[00:07:59] Hamish: it's the [00:08:00] same thing.
[00:08:00] Cam: The same as saying high value, but, but, but you've got better thermal conductivity.
[00:08:04] Yeah, because the material property you are, you let's you stack those two R four bats. So HD high density Yeah. Is the usual back burn that the manufacturers use. Those R four bats are usually 140 mil deep. Yeah. So you stack two of those, you get 280 mox. Your R eight that is north of 300 mil.
[00:08:25] Hamish: So it's just getting into a smaller amount instead.
[00:08:27] Cam: Yeah, it's
[00:08:28] Hamish: okay. So, so here's a question. You talked about slumping before. So our R six R for whatever they are, over time, potentially the value of that wall assembly could change if we're talking about in a roof space, you know, I mean that 300 tall bit of insulation might don't need to sag that. I thought they only go that way.
[00:08:53] Not like length winds like that. Doesn't throw that
[00:08:57] Cam: well in a, in a ceiling you will get [00:09:00] some slumping, but they have a binder to try and tain them off over the decades. Now if you're gonna wax stuff on top of 'em or you've got a layer of 400 dead rats or something Yeah, some kind of thick, it is gonna slum time and you will therefore produce the thermal performance of that, that bat.
[00:09:16] So what was normally our six wing installed that is now performing like our four. Right.
[00:09:20] Hamish: But that's why the rubbing probably is even better with external membranes and a ice and air tie. And with side, you're not getting things in there. You're not getting wind like it's sits there and it's done.
[00:09:32] Cam: Which is back at Al Goretex.
[00:09:33] Yeah. Will then jumper analogy. But the, the sumping problem's more problematic and a wall because it's course got gravity. So you've got a 1200 high bat. Yeah. And so you got the self supporting weight of that bat. And if you go a super lightweight, cheapo, fluffy bat,
[00:09:49] Matt: yes.
[00:09:49] Cam: Over time it starts sagging at the top.
[00:09:51] And so under your GaN, when install it, you put the bat heart up against the face of your kn. Now it's dropped down and you've got a 50 mil [00:10:00] gap.
[00:10:00] Hamish: And then as and as Jess says so, and she's probably stolen this from somebody else, you know, cold squats, eagle bottle spots. And if you've got that slumping at the top of the wall assembly, you've got a cold swap there, which could potentially lead to molded condensation.
[00:10:15] Cam: And from a thermal point of view, this is not a linear trouble. Yes. So you've got 1% non-coverage in that law, which is eminently doable. Even a relative diligent insulation installed means is and have some tiny steering. Yeah. Then you are reducing your thermal performance by your of 10%.
[00:10:35] Matt: Yeah,
[00:10:36] Cam: five. You know, if you have 5% non-coverage or 10%, which is far more common in your standard bill where the Yeah.
[00:10:42] Hamish: Cut out range. Your aircons, your power points, your, or anything to pipes, you know,
[00:10:47] Cam: then it's not, you're not having a 10% reduction if they're all four, but it's much, much greater than that. It could be 50% or more. So what you told your client, well, we're gonna have R two five in the walls is now performing like [00:11:00] R 1.2.
[00:11:01] Hamish: So I kind of want to go and go back and like broaden this out as a very basic concept with insulation. We insulate not just two walls, but I think most people think we do walls and ceilings, like they're the most common areas, but fours. And that means slabs and sub floors, both areal end
[00:11:23] Cam: Well, uh, yeah and this is where, that really does depend on what your climate is.
[00:11:27] So if you are so Perth, Sydney, or North, that ground cup flick. So you put a slab on gr straight on ground without any insulation can actually be beneficial because you can use the ground as a heat sink. Okay. So 'cause the grounds temperature, especially say Darwin or somewhere is gonna be as as cool as, or colder than the ambient temperature for much of the year.
[00:11:48] And it's stable too.
[00:11:49] Hamish: And it's stable so. So some floor they say Darwin just you insulate it
[00:11:52] Cam: probably
[00:11:53] Hamish: because you
[00:11:53] Cam: go if you're air conditioning your house. Yeah, because, and this is the other thing in insulation, isn't it? Oh uh, insulation is great for me in minter, [00:12:00] but it's costuming saunas like, well
[00:12:02] Hamish: I mean I'd also argue to be, without being a risk of circling back to a joke that we said before, it probably depends on how open that sun floor is as well.
[00:12:09] 'cause if it's on still yeah, it's completely openly got lots of wind washing. Then yeah, you probably want to each try to cover it, but if, if the air in there is relatively still, you're probably not gonna have, maybe that you've always got an exceptionally hum climate. Well, this is very true. Um, so you wouldn't just be, yeah.
[00:12:27] So now you wouldn't just have you, you'd bury your joints, your chipboard because the humidity would just soak into that shipboard, wouldn't then it be ship. We get mold and water. Yeah.
[00:12:35] Cam: Yeah. But, but a lot of that will depend on whether your air conditioning space. So think of your classic tropical home that's got the lewd windows very open and so outdoor remote, they, they operated pretty well in an extremely difficult climate because they were air conditioned.
[00:12:52] It's, once we started air conditioning those homes, you are driving the interior temperature below the exterior jut. [00:13:00] And so as that moist super hot mo, 9% relative air gets in through that wall or up through your cell floor, gets inside your, got your AC on the 25 degrees, it drops below. Dewpoint got this massive amount of moisture in that air ball.
[00:13:17] It's getting absorbed into your structural floor sheep and your trouble.
[00:13:21] Hamish: So this is probably, when you say moisture and stuff, talking about insulation, then all ins installations are different when it comes to touching your moisture and dealing with moisture as well. And just putting a certain insulation, a certain wall structure, always not the greatest.
[00:13:35] So we look at an old Victorian home that's weatherboard, clat hard will start plaster simply wacking a glass will, but in there might not be the best answer.
[00:13:45] Cam: No. So each, each material has different, uh, hydroscopic properties like ability to absorb moisture, both luco and and vapor. Uh, and so that's a, a head character sticker.
[00:13:57] Any insulation? No. Don't want it to absorb by [00:14:00] general. You don't wanna to absorb or you, you
[00:14:02] Hamish: want to be hydrophobic.
[00:14:03] Cam: Yeah, that's right. Yeah. You don't, you want to get rid of that, that moisture
[00:14:07] Hamish: throat hydrophobic or stop it from getting wet.
[00:14:10] Cam: Well, yeah, but you could always assume, you know, assume worst case somehow I about guess that this is gonna get a plumbing leak, something's gonna happen.
[00:14:18] Can it dry? Yeah. And so most of our insulation products, our standard, the glass will be treated with the chemicals to try and, uh, reduce the ability for them to absorb that moisture. But as we know where the glass will back, if you leave it outside in the rain, it mats up together and it's cactus. You gotta check it.
[00:14:34] Hamish: I like that. We've gone back to types of render and I'm not sure if you know the answer to this and I'm probably then just, um, gonna be relying on what your opinion on this depends. So I built a hen house, right? And I know Brad's built a head of hem house as well. My particular example had render on the outside and render on the inside.
[00:14:54] Right? And in my mind that was um, for the air tightness and [00:15:00] we're resistive. Now hemp, the hemp walls that we are building are 300 wide. Now how that assembly is working from an uh, an R value point of view is the same theory as a glass wall. It's trapping air in there. Now, if we're not rendering the inside, 'cause I know it is different if you're not rendering the inside, if we're not rendering the inside, which is the warm side of the assembly, are you still going to get wind washing?
[00:15:35] On the inside. Is it gonna impact the arvo of that wall if we haven't rendered to the inside?
[00:15:40] Cam: Only very marginal,
[00:15:41] Hamish: yeah.
[00:15:42] Cam: Okay. Beca, because the wind, the influence of wind washing is, is affected by density. If I have my, let's go back to glass walls. Our yard where you get your standard ceiling back, you know, was very light and fluffy thing.
[00:15:54] You pick up that middle of tags, you know, clearly far more air than [00:16:00] glass.
[00:16:00] Hamish: Yes.
[00:16:01] Cam: If you blow air past that, it quite easily scours and get very deep into the loft and therefore reduces the thermal performance. If I go to a higher density wall bat, or I go to start jumping to other fibrous products like the winow walls.
[00:16:16] Your Rockwall type products. Yeah. Which are, you know, about 80 kilogram per UIC meter density as goes to your high twenties at most for glass. And you've got far a far denser product. Far smaller. Air gaps and so a much, it's much more difficult for the air to move into that space.
[00:16:35] Hamish: So, so then that is the same with, uh, mineral wall or rock wall when you're using that as an outside of that weather resistive barrier, where, and I think it's a conversation I had with you, you know, isn't this being impacted by wind washing?
[00:16:52] Because our ventilator cavity is then immediately on the outside of that exposed rock ball. But I think then your comment was, [00:17:00] because it's so dense, it's negligible. That and was, there's a study somewhere they, like, they did a study on this and they, I think once it hits a certain density, I had 96 grams of Q meter.
[00:17:10] It actually been washing fractally, just goes, and it's the same for, for my fiber as well.
[00:17:16] Cam: Yeah. Yeah. And so again, it's a, the, the first metric you look at is density. Yeah. So you send the wood fiber voids in the order of maybe 60 kilogram per meter density. Yeah. So again, twice that is your best glass for Yep.
[00:17:27] Getting towards your rock wall type density.
[00:17:30] Hamish: If you've got a dense insulation like hemp or rock wall or, um, wood fiber. Do we also see benefits of thermal mass in those particular products? And thermal? Can you explain how thermal mass is in situation, either the two different things?
[00:17:47] Cam: Uh, so yes, the denser of the product is inherently, it's got more weight to it, and weight is related to the ability of, of a material absorb container heat.
[00:17:57] Um, what is thermal mass? [00:18:00] It's, it's a, it's a, we, it's character, material character to store heat, but in order to store that heat, it needs to be able to absorb that heat. And so a material with very high thermal mass is classic examples. Unlike concrete. Very high thermal mass, yes, but also very poor insulator because the app, the inherent ability of that material to absorb heat also means it's very good at conducting that heat.
[00:18:26] And so if I use, say a precast concrete wall and put it on the interior of my building, then it's got very good thermal mass, but very poor, very poor thermal resistance because it absorbs that heat, allows that heat to carry through the depth of that precast wall and it just disappears towards the exterior.
[00:18:46] Hamish: So now for like my house for example, the moment I have a slab and stand the suburb port, I'm now about to put 75 mil XPS insulation on top. And then I'm gonna pull a hundred, I think a hundred mil of infill concrete is that now [00:19:00] getting the vest of both wheels where I've got a great from my sucker battery for the home, but also that that complete in continual slayer is a, is stopping that resistance that he'd been able to trouble through.
[00:19:11] Cam: Yeah. That, that's basically right. Exactly. So you, your, your screen, your fine finish on slope on top of the XPS is providing really good thermal mass. It's not conducting through to the exterior to the ground because you put the XPS in between. No. And your battery analogy is perfect because you think about it out that the electricity grid batteries do not create electricity.
[00:19:33] Things that create bulk electricity are your fossil fuel power plants. Your winds, your solar plants. Yeah. They're the ones that create the electrons. The battery's just storing it. You've got no means of generating those electrons in the first place. There's no point handling the bash in the same way as with thermal mass.
[00:19:51] It's just a store of heat. It's not a creator of heat.
[00:19:55] Hamish: Does it matter as much in a passive house?
[00:19:58] Cam: No, because the passive house has [00:20:00] inherently got a hy thermal inertia tablet.
[00:20:02] Hamish: So let's talk about passive house certified passive house modeled, um, lower door hitting all the metrics, certified plap on the wall.
[00:20:10] Does that house perform differently? If the clients are living in there showering, eating, and there's no furniture, they're just sleeping on the ground, does that house perform like noticeably different than if there was furniture in the house?
[00:20:25] Cam: So it will almost certainly tanks are fluctuate a bit more than the house with lots of thermal mass be that for Aja and Peanut.
[00:20:33] Hamish: Yeah. Okay. Uh, and, and, and is any of that taken into consideration when you are modeling? So there's
[00:20:40] Cam: some standard factors that are applied, but, but, but again, it, it's far less important than in a buil house because the way in which you do that envelope is creating the thermal inertia itself. That tractor mass within the house, you know.
[00:20:56] We're reassuming, there's cabinetry in there and there's another and a whole bunch of [00:21:00] other stuff. You know, there's tons and tons of stuff in our houses. Yeah. All of which inherently add out that too.
[00:21:06] Hamish: So I wanna go back to insulation where we talk about roofs. And let's just assume a trust roof for a minute.
[00:21:13] Should, should we be inside at the bottom cord or hit it at the top cord? Like the warm roof first. Cold roof. Because then the second question tonight, is a warm roof insulating at the top cord? Or is warm roof insulating externally? I dunno about you, but where does design you with rafters? Constantly at the moment.
[00:21:31] 'cause there is that cause now in the NCC. That pretty much means you have to inte like at the top quarter. It's, I mean, it's also tricky too. 'cause if you start talking about coal brews, you gotta like the NCC state and you gotta ventilate that. As in, if we're talking about, um, air type buildings, possible, I mean, it technically is above your, or most cases above your, um, intelligent membrane.
[00:21:53] But if you don't have an intelligent membrane and you have a cold roof and you're relying on your [00:22:00] external membrane to create air tightness, then you're potentially creating an issue up there. But that's a bit's. Let's here to go back a sec. I can imagine, like you have to now have your external rack, not airtight.
[00:22:12] Cam: And so the construction code, essentially it's requiring you ensure that external membrane is not airtight. You've gotta have that opening. The, if you've got the potential for wind washing across those like fluffy bats, be as you're laying that air coming into the, even draw across the top of the bat.
[00:22:25] And so what you're seeing, a lot of details, not so much in Australia, means actually is I'll put a bi and that first meter or two in from the eve, just a bit of ply or something. That's
[00:22:36] Hamish: assuming you have an eve though.
[00:22:38] Cam: Oh, well, at at least, at least from wherever that gap is on top of the wall over that first meter or two of the bats, just where that is coming in to reduce that scour heavy washing effect or the bat is that it loops through that void and up out through just
[00:22:53] Hamish: like sitting here like thinking there's so many fucking things you need to think about when you're building a house that could create risk.
[00:22:59] Like, [00:23:00] and, and, and you know, this is where I kind of go back to the own like and spend talks at this a lot. Your real insurance policy is a certified passive house. That's your insurance policy right there.
[00:23:12] Cam: Yeah. Uh, absolutely. The quality checking process with passive house is what you are buying. Is buying.
[00:23:19] Hamish: Yeah. Correct. Now I, it, it, now, you know, potential clients doesn't do this for about me and Matt. Like we, I would say our good builders and we think about all of these things. So I guess the risk when people are employing us is lower, but I'm thinking about, um, people who are listening to this podcast and their brains just exploding now just thinking, fuck, how am I managing all this risk?
[00:23:43] A really easy solution is just to get a certified building.
[00:23:46] Cam: Yes. But I think key phrase there is managing risk. It's not zero risk.
[00:23:53] Hamish: Yes.
[00:23:53] Cam: We all we can do in life is manage and mitigate the risk as best we possibly can.
[00:23:59] Hamish: Yep. Yeah. If you're a [00:24:00] young kid starting out, or a young builder or a young architect, I think it's really important that you do your first two, three houses.
[00:24:05] As a certify cannot certify you so you know what to expect. Yeah, exactly. So you know what the process is. So it becomes part of just process. And this is the issue on now hand, this is a whole other conversation, is the apprentices that we're now producing only know one way. Boom. And it's awesome. Do So what happens when they want to go up by themselves and they have to pick up the other nine artists of the work that's out there, that's pure crap.
[00:24:25] Now what do they do? Because they're not, they're not designed and haven't been taught to build to a L standard, and how do they kick up that first job? Because they're gonna be way more expensive. Yeah. Well, I mean, let's hope by the time that happens that the, that the actual in the level of quality and the, the, the standard increases and they have to, and they have to, and then there's education from clients coming through.
[00:24:48] You know, I feel like, you know, every day that goes past, now there's more and more people demanding this stuff. Like I'd have everyone demands it, but can they afford it? And there's an well, a message on [00:25:00] top. Yeah. But, but that's okay. So if they, if they're. If their number one goal is to have a healthy building, let's forget about energy, fish renewal, that kind of stuff.
[00:25:08] If their number one goal is to have a healthy building, then everything else falls underneath that. So the, the, the joinery, the finishes, the fixtures, all of that becomes secondary to performance. If, if that swings around and, and aesthetics and everything like that is for a top priority. Well, I know that building's not for me.
[00:25:27] It's, it's, you know, I'll just walk away from it and I'm starting to see more and more people. Well, a hundred percent of people come to me wanting performance. I just wanna go back to a full, we just talked about 50 back testing and rounding off insulation testing. Inte is very important. Um, and it's not as simple as just picking up the thermal camera and walking around and checking, because that doesn't tell you the answers.
[00:25:52] You need to do, it needs to be difference from temperature inside to outside to actually check it.
[00:25:57] Cam: And, and remember, and this comes back to our discussion, re [00:26:00] conduction and the action radiation. What's, what's the thermal camera measuring? It's measuring radiation. And what did we say about radiation? It's a material property.
[00:26:08] So different materials in at different ways. So a material, I could have a black material and a white material at the same temperature, but they will be emitting differently and therefore they will like here to be a different temperature on your thermal imager.
[00:26:23] Hamish: Yeah. So it's, so really the best way to do a thermal imaging ca, like how we test our insulation.
[00:26:28] We'll do a visual author and kind of have a team on site visually watching why they're getting installed. I don't know the people that we use actually care about and stuff. So they are documenting too. They'll document the corner and how they'd installed it. So there is that reference point. And then we'll try as best that we can to either eat or call the house and sign.
[00:26:48] And go around with a camera and check it. And sometimes it's really, really hard. Sometimes we physically can't do it. In winter coming up it's a bit easier, but in summer when it's a hot day, it can be quite difficult.
[00:26:58] Cam: And, and that's a [00:27:00] perfectly valid use of a similar image of assuming as I think the man, you've got this stu tray, you've got the glass wall in there, or polyester, whatever that the insulation it is bio plasible and, and membranes going on.
[00:27:12] So as long as you'll be looking in that frame, only at the wall and not the wall and the window together. Because the window will give you spurious results. Yes, because it's, it, it's in mis is vastly different to that if the glass wall and the timber.
[00:27:26] Hamish: So you kinda have to be up close really? Or
[00:27:28] Cam: you, you just, just focus your effort on.
[00:27:31] You know, it's a, that it means you were looking at this cy to what's on the, in the field of view of the sensor.
[00:27:36] Hamish: Yeah.
[00:27:36] Cam: And you're just looking within that space and going, right, here's my wall cavity. There's four bays here. There's a little purpley dark colored spot right there in that corner. I'm not sure if got that bat right in there, what it put out.
[00:27:47] Hamish: Yeah. And how much can you compress those backs? Because by what percentage can we, 'cause sometimes we've used the, when we do the, um, internal cavity bat, we actually saw 50 mil polyester, which they're quite dense, but our patterns [00:28:00] are only 45. We also usually put a final packer, so we're not compressing it.
[00:28:04] But you can compress them slightly.
[00:28:06] Cam: Yeah. You, you ca you can to an extent, and again, it depends on the density of the bat to start with. So the way away fluffy glass wall backs, you can compress a, uh, an thelist now and it's caught 10 to 20% maybe. Um, what really matters with insulation as it's continuity.
[00:28:22] So exactly what you're talking about with thermal imager, m being diligent and installing it. Make sure you've got a perfectly. Install it in those cavities. A bit of modest compression. I wouldn't be too fussed about. It's, it's that continuity there. Yeah.
[00:28:38] Hamish: And that means like, around the windows is like spray foam here, uh, with a closed self spray foam or ing in some glass or like, we really need to, you, you've gotta make sure that it is in Melbourne, because I know it depends where you are.
[00:28:52] We want that 360 layup around that whole house. Um, this is a nice segue to probably a question I've got [00:29:00] now. Whenever we've done slabs, I've always got off cuts at XVS. Right. And it just kills me that, that just gets thrown away. Right? There's not a huge amount, there's no recycling facilities at the moment.
[00:29:13] I know that there is some chatter at the moment that, that's starting to change. Now. We've just, we keep all of ours and then we use it for our external wall junctions. Now someone has actually asked me before, are you worried about. Any risk there because I, I just think in my mind, well that can get wet.
[00:29:33] It's not gonna get covered up like immediately. And we just put it in as we're framing so it doesn't get forgotten about. Is there a risk in our climate, which is reasonably mild of using XBS blocks in that law junction?
[00:29:48] Cam: So in a heating dominated climate, remember what you want fundamentally is you want increasing vapor pers Yes.
[00:29:56] As you move out through your assembly.
[00:29:58] Hamish: Yes.
[00:29:59] Cam: And so a [00:30:00] foam, like an XPS is relatively vapor impermeable. Yes. Whereas something like glass wool is very vapor permeable.
[00:30:08] Hamish: Yeah.
[00:30:08] Cam: So your ideal assembly is, you know, this is an imaginary assembly course, but if you've got an under frame, we wake XPS on the interior face and put glass full on the outside.
[00:30:20] Matt: Yeah.
[00:30:20] Cam: That's better in your heating dominated climate than the inverse of putting the XPS on the outside.
[00:30:26] Hamish: Yeah.
[00:30:27] Cam: But. In the summer it's reversed, so I'm not, no one should go away and actually build what I've just described. I are those two options because they're both scary, scary written all over them.
[00:30:39] Because in the summer, if you build that first option, especially on the inside of the stud in Melbourne, then the vapor drug is towards the interior. When you air condition your house, depending on what set point temperature you have it at, and depending on the thickness of the XPS versus the glass full, you might have be below the viewpoint.
[00:30:58] Hamish: What we're talking about now [00:31:00] is, is great because it's getting people thinking that's getting because, because there's not one solution for every different scenario. Yeah. Okay. So in your professional opinion, should we stop using those XBS off cuts in that scenario?
[00:31:17] Cam: Well, you are also putting an internal lawyer in vapor control in Correct.
[00:31:21] And you for HRV. Yes. And so on that basis, and as you said, you build in a relatively mild rec client held, uh, then the risks are reduced. Right. Doing that. Now, if you told me I had so much XPS in this job, so I've just whacked it along with the outside of my one 40 frame No. On a whole facade. No. Then I've got a problem with that.
[00:31:41] Yeah. But it intuitively, it feels like in isolated spots like that all junctions where you've got a tricky little corner. Okay.
[00:31:52] Hamish: And there's obviously a couple of reasons why I like to got one that, that doesn't get forgot to get wet, but also it's suffering that experie going into landfill and it's getting a [00:32:00] reimagined life.
[00:32:02] Yeah. Um, I wonder if we leave with their cam, like I think, um, I'm going to, I. Really enjoy, just think back to this and probably have to listen to it to a few for a few times. 'cause there's so much to unpack there. Um, but also I love this episode because I think it's gonna get a lot of people just thinking it's gonna make people stop and think because as we, uh, demonstrated, knock all insulation is equal.
[00:32:34] They're all different. They're all for different purposes. Um, perform differently under different conditions. Um, and I think the massive, the biggest takeaway is modeling, wolfie analysis, managing moisture. Oh, what else is there? Add to, that's the word. The depending, there's a lot of depending. There's a lot of depending.
[00:32:53] Yeah. And there's not one kind of like vinegar stroke, which just is, well, this is how we should build. [00:33:00] Like, it depends.
[00:33:01] Cam: Yeah. I, I think we've gotta set aside the black and white. That worth that will fail.
[00:33:05] Hamish: Yeah. '
[00:33:05] Cam: cause we cannot, we can't say that definitively on any one project, any one location. It's a game of probabilities and we're simply trying to reduce the probability of bad things happening.
[00:33:16]