Roof Insulation Design for H1 Standards

[Shane Clarke] Welcome to our last webinar for the year. You can probably tell it's December. Thank you very much for all that have joined us. We did ask, we put a quick poll out there last week and said anyone interested in learning about the new H1 that has been raised by MBIE and we've got overwhelming response. So we very quickly last minute through this webinar together that might not be as polished as the normal ones, but we managed to grab Jason Quinn from our last webinar as well. So thank you, Jason. For those of you who don't know, Jason is the manager at Sustainable Engineering and he got bored of being a rocket scientist at NASA. So I told him to come to New Zealand and be a building scientist. A bit of a challenge. And also have Peter Mills with me on the panel, who's our internal technical consultant who plays with our BRCA software for working in our condensation points for roofs and things like that. So we'll talk to him later about what he's come up with. Today we want to obviously talk about the impact that the new H1 requirements have, particularly around the schedule method for roofs. We're going to cover what the new H1 requirements are. Hopefully we're going to cover some of the possible unintended consequences of the increased insulation in our roof. And we want to obviously give you what we think is our best practise when it comes to warm roofs, flat roofs, filling roofs, etc. So those are the things we're going to cover today. We're going to start with a bit of a poll. So by all means, get involved, get the keyboard going and just keen to learn when you think you'll be designing to the new H1 levels. Give you a couple of minutes to populate that. Alright, thank you for that folks. So we're scheduled for around about 30 minutes and then we're going to have a bit of a Q&A at the end. So if you've got some questions, by all means, feel free to chuck them into the questions box and we'll get a chance, we'll go through and answer those at the end. Usually we get a lot of questions, we don't have a chance to answer them all. So what we'll do is we'll send a recording of this webinar to all the people who have signed in and you'll get a copy obviously of the webinar and also get a copy of the Q&A that we've covered as well. Alright, so without further ado, we'll start with you Jason. Then we'll talk about obviously roof insulation, the new revised H1, particularly around the schedule method. And I guess, yeah, I guess the first slide is we've got some new zones. [Jason Quinn] Yeah, so yeah, so we'll talk about H1, AS1 and AS2, right, so both for homes and for non-residential buildings, just the roof stuff. So yeah, so we finally have climate zones that make sense from a like actual climate point of view. So like it's colder in Queenstown than Nelson and there's some variation across the country. It's quite funny because all these climate zones were actually developed by NIWA like 20 years ago or something, right, or 15 years ago. And then what they did for this particular version of the building code is they tried to figure out what's the fewest that actually made sense from a physics point of view in terms of energy use in buildings and ends up with this. So it's quite a good thing. Yeah, so six climate zones and it even includes, you know, Chatham Island, which is great. [Shane Clarke] Yeah, right. So there was three originally, wasn't it? We had three? [Jason Quinn] Yeah, we had three and yeah, so they developed the 18 zones and we dropped down to three before the last building code update, which is for insulation. And the reason they did that was there's a lot of commercial work done to try to push for that because the South Island is a relatively small consumer base versus much of the North Island for the population. So anyways, it just doesn't make sense, especially when you're trying to save energy across the country. All right, so we've got six climate zones. But the funny thing is for H1AS1, the schedule method says you have to use R6.6 across the entire country. So we should all take advantage of this to make fun of MBIE when we get a chance because, you know, they enjoy it. And as long as it's well meant. So we've gone from roughly an R3-ish kind of roof to R6.6. So roughly a doubling of the insulation requirements because insulation is roughly just due to thickness. So it means your roof insulation's got twice as thick now unless you increase the performance of insulation. Wow. OK. And then if you think 6.6 for buildings is a big change, look at commercial buildings, which have gone from very, very little insulation in our large buildings, R2-ish, up to R7 down in the South Island. So and even, you know, twice that effectively in our warmest climate zones. So a big change. Now, both these changes were done to try to hit about 40 percent heating energy savings in homes and for large buildings to hit about a 20 percent energy savings. So a lot of that was due to this roof change. And we could argue as to why they made just the roof change versus wall changes and other things. But MBIE has basically said they just felt it was something that was achievable from the New Zealand market to do this. And it's early on. We've done a lot of buildings with this kind of R values. [Shane Clarke] So last week we talked about walls being sensitive. That PC word sensitive. Are roofs not as sensitive or how can we sort of exceed? [Jason Quinn] Yeah, to some extent, they're more sensitive, but they're a little bit easier to deal with. So when our most common construction, the one that probably MBIE had in mind when they laid this out was a, you know, a vented attic roof or what Peter typically calls a cold roof assembly where you've got, you know, you've got a gypsum board ceiling or some other nice air control layer on the ceiling. You've got insulation on top and then above that it's ventilated outside air. So the important thing, and we'll actually the next slide, the good one to get into, you know, it's all about keeping that warm, moist air from getting into that attic space or to get above the insulation, because once it does that, unless it's bent up very quickly, you get condensation. And if the air flow rate's too high, you get the condensation, even if you have a good vent, right? So it's really common if you crawl around in attic spaces in colder climates like in Queenstown and you look at a normal vented attic roof, which has got a good gypsum board, well-stocked gypsum board layer, but they put a can light in the bathroom for some crazy reason, which means they've got a big hole in the ceiling in the bathroom. And you'll see mould on the, if they've got a rigid sarking, like an OSB sarking under the roof, because they've got an asphalt shingle roof in Queenstown and a few houses like that, we'll often have mould underneath on that asphalt, on that OSB, because there's moisture coming up to that roof and it's hitting the underside of that roof and condensing and causing condensation, causing water and then mould. So this is pulled out of the insulation guide that you guys talked about from last week, but it's exactly applicable to roofs, right? So this, pretend this is a roof instead of a wall, because it looks like a roof in this picture. And you've got warm, moist air inside the building. And if it can get up and go into the insulation layer, then you can have a problem. But you've got this wrap layer, this water air vapour control layer, the green one, which is keeping that moist air from going into that insulation at a high enough rate that it causes a moisture problem. And then any moisture that does get through, because it's ventilated above the insulation, can ventilate out of the building safely without an issue. So that's kind of the main thing. When you go to these high R-value assemblies and roofs, it's really important you control air control. That's like the main thing, is make sure you don't have air leaks in that ceiling assembly. If you've got big air leaks, it actually doesn't matter what kind of insulation you've got. You're going to have a problem. And the more insulation we put in, the less, I guess, when you have a wall that's better insulated, you're saving money because you're not putting as much energy through that wall or roof. And because you're putting less energy through it, there's less drying potential that occurs in that insulation layer, if it's thicker. So the same amount of moisture that used to be okay, like you got away with it before, because it was fine. You didn't get away with it. That was actually a good design. Now, if you don't have better air control, you're going to have moisture problems you didn't have before. So in Branz talk, I mean, I'm sorry, MBIE talked about that quite a bit with their unattended consequences, which I never did count how many times they said that, but I'm sure it was over 20 times. [Shane Clarke] Excellent, thanks for that, Jason. We'll chip in when we move on to the next section. But what we've got now, we've got Peter Mills, who's our internal technical advisor, who's going through a couple of roof assemblies that he's been working with. He's used his BRCA software to come up with a couple of ideas. And this is some suggestions and some considerations from our perspective on things to look for when you're designing your new H1 compliant roof. So welcome, Peter. [Peter Mills] Hey, thanks, Shane. So with these calculations, we've considered a range of different roof constructions that you can use. It doesn't encompass everything, and there are slightly different ways that you can do it. But these are mostly our acknowledgements of popular ways to do it and suggestions of how these can work and how they should be done. So if we move to the first slide, we've got pretty much the standard way that New Zealand houses with attics are constructed. You've got your gib, you've got your framing above that, and then you've got insulation between that framing and above it. This still works under the new kind of requirements. You're probably looking at about 250 mils of insulation, and it works provided there's good ventilation. If there isn't good ventilation on this roof, there's a very high likelihood that there's going to be condensation. So that's a pretty critical aspect of it. [Shane Clarke] And what sort of insulation have you used for this calculation, Pete? [Peter Mills] So we've used a high performance lofted insulation. So a lot of designs and constructions at the moment are using very standard lofted insulation, which has a lambda value of about 0.04. And lambda value relates to R value. So the less lambda value you have, the better. So what we've used for these calculations, wherever there's that lofted insulation, is a high performance one. So if you were to use the kind of standard lofted insulation that people tend to use, in this build up alone, you'd be looking at about another 30 or 40 millimetres of it. So you'd be going from a build up that's about 260 mil to about 300. [Shane Clarke] Yeah, yeah, right. So in this build up here, it's obviously very important to control the airflow to make sure you've got enough drying capacity. [Jason Quinn] Yeah, yeah, yeah, yeah. And that's what the gypsum board ceiling does. Yeah, nice. Okay. [Shane Clarke] Makes it a little difficult to walk on the rafters if you ever wanted to use that space, I guess, if it's all covered with teddy bear stuffing. [Peter Mills] Yeah, it was previously difficult to do this. Now it's going to be worse still, because now there's going to be a layer of about 100 to 150 mils of lofted insulation on top of that. You can buy little standoffs to kind of get that space back, but that doesn't really make as much sense as the next slide, where you're actually getting that whole cavity back by putting that insulation into the rafter assembly. So what we've got here is what we call a hybrid warm attic roof approach. So if we look at the diagram here, there's a bright green line for the vapour blocker layer as part of that wrap. And then we've got a PIR high performance rigid insulation above that. So that's going to do the bulk of the work here. And then below that, you've got our high performance lofted insulation to make up the rest of that R value. So all of this is basically sitting underneath the roof and because of those two wrap layers, there's no opportunity for condensation. So there's less reliance on good ventilation in that space and just better control of it. [Shane Clarke] OK, so what we've got here is we've got a conditioned space within the attic. We also have a drying capacity above the outer layer of insulation, right, which we've touched on is pretty important. [Peter Mills] Yeah, yeah. What we find is this conditioned space is actually better for mechanical ventilation as well. Because there's an opportunity for condensation within that system just because it's all conditioned. With this one, you're already looking at a thinner insulation build overall. That's majority due to the PIR, but it is actually because that high performance layer isn't being broken by the timber. Because in the previous one, you would have your high performance insulation and you've got these timber members breaking it up and actually compromising the performance of that material. That doesn't happen here. It's unbroken, which actually this build up lends itself also to connecting with warm walls because that green wrap layer can actually connect to your wrap on your walls and the insulation can do so as well. Whereas with that previous assembly, you're going to have a really hard time doing that. [Shane Clarke] Sure. OK, and then on to the next slide, which is obviously right in our wheelhouse, flat roofs. [Peter Mills] Yep, so we thought we'd start off with our least favourite assembly at this point. So this is a cold membrane roof. We are of the opinion that these should not be allowed anymore. They were already difficult to design and instal without problems. Now they're going to be nearly impossible. With this kind of build up, it is very critical that there's adequate ventilation and with the build up that we're looking here of about 260 millimetres of insulation, when you've got things like nogging to the underside of that plywood, it's going to be really, really difficult to get that correct airflow. If there's not correct airflow, it tends to custom. There's a lot of condensation that's going to form under there. It's going to drip into the lofted insulation, reduce its performance, cause all sorts of issues. So yeah, avoid this at all costs is our advice. [Shane Clarke] Yeah, like Jason was mentioning before, if we've got airflow above the insulation, we're OK. But we do know from our experience that it's very, very difficult to get adequate airflow above that insulation layer because it's rammed up so close to the surface of the plywood. And I guess the other thing is with a flat roof, you just don't have that thermal drive because you have no slope for the heat to rise. [Jason Quinn] Yeah, in practise, it's really bloody hard for the poor builder, right? It's easy for designers to draw a roof with a mushroom vent every 40 square metres, the way the specs say, right? It's easy to draw that, but the poor builder, when he's putting it in, he's got to put blocking in at the edge of the sheets. And then, you know, there's a skylight somewhere that causes blocking problems. It really pushes the risk and the difficulty onto the builder, and I don't think it's appropriate anymore. [Shane Clarke] Yeah, and typically you'd have timber running 400 centres both ways, so you're creating these little cells, so you'd almost have a vent every 400 millimetre square, which would have a unique look, I guess. [Peter Mills] I guess what's probably important to mention here is actually the build thickness, because a lot of times when flat roofs are selected, the height and the build of that roof is really critical. In the previous assembly, I think we were looking at about 340 mils thickness. In this ideal scenario, the warm roof, we're only looking at about 320, 315, and that's because we're able to use an unbroken high-performance PIR layer. So there's no compromising of that thermal performance. So we've only got about 140 mils of PIR, and that gets you the new H1 standard right away. And then all you have to worry about at that point is getting the correct structural framing underneath it. If you don't know about warm roofs, we're probably not going to explain this kind here, because there's a bunch of other webinars where we've talked about it at great length. I don't really have anything else to add about this one. [Shane Clarke] That's a good point. I mean, if you are on the Nuralite website and you're looking to design and specify a flat roof, it is almost impossible for you to specify a cold roof from our website now. We are leading you down, intentionally leading you down the path to specify a warm roof, because overhabitable space. I mean, the only place we see a cold roof is, you know, a dog pen or a bus shelter, perhaps. But apart from that, we're strongly directing people down the warm roof route. [Jason Quinn] Yeah, I do want to make one point is, regardless of which vendor you pick for warm roofs, that green layer where you've got an air vapour control layer right there on top of that outside fly layer, that's a really, really important layer. And that should be a fully adhered layer. There are still a couple warmer suppliers that aren't necessarily requiring that in all the climates. And in my opinion, it should be required in all the climates. So just be aware of that. So you guys have a bit of an advantage there. Maybe you didn't want to mention that. [Shane Clarke] Yeah, no, very, very important. As Jason's previous slide, he showed us the building science slide there, we're talking about stopping that warm moisture rising up into the structure, into that cavity. And that's what that green line does. So, I mean, in our case, it's actually a full aluminium foil vapour blocker, but it's not smart. It doesn't breathe one way and go the other way. It does absolutely nothing and just stops everything. [Jason Quinn] Which is appropriate below a PIR layer. [Shane Clarke] Yes. [Jason Quinn] The right thing to do. [Shane Clarke] Yeah. All right, Pete, you got a solution for some Scillian roofs there? I've actually got a question coming about Scillian roofs, so I'll be watching intently. So if we can go to the next couple of slides there. [Peter Mills] Yep. So this is a kind of cathedral ceiling, I guess is what you'd call it. And this is a traditional way that you'd do it. You'd have your exposed rafters, some plywood or sarking that would be visual. And then you've got your high performance bats in that void there. You'd be looking about 270 mil of that. In this case, you'd have your wrap after that. And this works because the roof batten above that wrap allows the system to ventilate. It's pretty wieldy, like you're going to have about half a metre for this build up if you can see the little numbers here. Right. There's a more ideal way to do this. [Shane Clarke] I didn't actually see that number, Pete. Is that half a metre thick roof? Yep. Right. OK. [Peter Mills] So what's your idea? Well, the next example cuts down by at least about 100 mil. So this is the Gerard Thermacore roof that we're looking here. Effectively, that top roof cladding could be replaced with a range of different options. But in this case, it makes sense for us to do roofing tiles here. So what we've basically done is we have replaced that high performance bats with a high performance rigid PIR layer and a full vapour blocker underneath it. So there's no way that any kind of moisture vapour is going to get through that insulation. And you only need about 150 mils of it to get that full H1 R value. And that's how we're able to cut down on the height of it quite significantly. [Shane Clarke] Excellent. And again, it's got that, I guess we call it a redundancy layer above that insulation to allow for that drying capacity. [Peter Mills] Yeah. And in this sense, that layer is for kind of water repellency, whereas the vapour barrier underneath the PIR is actually for the air control. [Shane Clarke] OK, excellent. And onto the next part of the H1 calculations, we talked about commercial roofs. [Peter Mills] Yep. So these are going to get more popular, is my personal prediction. This is the diamond tricore system where you have a metal tray over purlins and then you've got the high performance PIR insulation. In this case, again, it's going to be 150 millimetres thick to give you that R6.6. It's actually shooting above it. Then you've got your wrap layer above that to control the dynamics. You've got a batten above that, which actually allows for airflow to stop condensation and also allow for movement. And then you've got your top metal tray. The batten in this case is underrated. It does a lot of things that people don't really appreciate. And it is highly recommended if you're going to go for a system like this. I guess that kind of leads into the next slide. So this is a kind of recent system that has come into the market where lofted insulation is put between two layers of metal. All we can really say about this one is that the airflow is critical for the system. If for whatever reason there isn't proper vapour control of that first tray, and if there isn't good enough airflow under that top skin, there is a high likelihood that there is going to be condensation. And like Jason mentioned earlier, because there's so much insulation on this build, there's not a lot of energy to dry out that space. Despite being the top skin of a roof, in this example, it's still going to take two months to dry out whatever condensation is getting in there. So I guess our message for this one is to just be careful and consider the possible unintended consequences of this build up. [Shane Clarke] Yeah, no, absolutely. Obviously, we never actually came to a result on that calculation. Ended up with a question mark there, and it's dependent on so many things. It's dependent on that metal tray under skin being completely airtight to stop that moisture air rising. I haven't seen two sheets of metal flipped over one another to create an airtight seal ever, so something to consider there. Good points all around. Alright, so just to quickly summarise what we're trying to cover today. So we're saying that installing a wrapped layer is very important. So that's your water air vapour control layer. No matter what you're doing, that's probably the key takeaway there. It's going to improve your roof performance and reduce your risk. It's going to give you that sort of level of redundancy that you may need, because this conditions change and building uses change and things like that. I think even just a simple repaint of your roof, changing the colour can actually change the way your roof performs in a drying capacity. We've illustrated the airflow above the insulation layer is needed to get rid of that moisture. [Peter Mills] Yeah, and it makes it quite difficult for that last example because they'll have thermal bridges through the kind of metal supports for that top skin, but they're only periodic. The only way I can look at it is through the top skin. [Shane Clarke] Yeah, so I mean, who would do that sort of thing, Jason, like we we just use our good on you. [Jason Quinn] Yeah. We've got a, we've got a couple of skill folks to it. [Shane Clarke] Yeah, yeah. So we're, we're just using the software just to take a two dimensional snapshot to get a, you know, a complete answer you'd need to engage the likes of Jason who can do, I guess, a more in depth analysis of what we're trying to build. [Jason Quinn] Yeah, although I have to admit that most of the time I do that more in depth analysis tell you that you should change the roof. So it looks like more like one that Peter can model. A lot of times when you hit complexity, the better thing to do is not to figure out complexity, but just to make it simpler. Right, right. I mean, I love doing complicated stuff. [Shane Clarke] And the other piece of your summary is that we're saying that PIR insulation is a very useful way to achieve high insulation value simply because of the great thermal resistance that the PIR board provides. All right. So that's us. That was us. That was our webinar. That's our summary. Now we've got a few questions from the, from the audience, which is quite good. I like this one, and we shouldn't have assumed everything. What's the schedule method? Great question. [Jason Quinn] So, should I take that one? So, in the new and old H1, there's effectively three methods you can use to prove that you have sufficient insulation in your building. The first one is a schedule method. So, you have to have that you just say that the R value, you just show that the R value for your walls and your roof and your windows and your floor are above a certain number. And you can do that by just referencing the brand's home insulation guide, which is what most commonly everyone does, or using design navigator online or using a more complicated tool like pass off 20 package, or BECCS, right? That's a schedule method. So it's kind of the simplest one. Then there's the calculation method, where you can kind of offset for a certain glazing ratio on homes, you're allowed to say, I'll make the roof a little bit thinner and I'll make the wall a little better. And you can do a simple, like a simple hand calculation with pencil, show it's good enough, right? And then finally, there's a modelling method. And actually, it's something we didn't talk about because we were just talking about schedule method here. But in the new H1 code, not the acceptable solutions, but the verification methods, they've got a modelling methodology. And in that you can basically model a building that's built as per the schedule method. And then a building built the way you're actually going to build it and show that the whole building meets the standard. Because a lot of our certified pass houses in New Zealand, which are much more efficient than this standard is trying to achieve, have less than an R6.6 roof. But they've got much, much better windows than what's required in the schedule method. So on the balance, they're still much more efficient than the schedule method building. Hopefully I didn't lose you there. We may have lost you. All right, let's keep going then. [Shane Clarke] Folks, I'm back. [Jason Quinn] Well done, Shane. That is an awesome strategy. I can be in two places at once. Sorry about that, folks. Yeah, yeah. So, yeah, so I think we finished the schedule method question. Yeah, so the modelling method has changed in each one of the new verification methodologies. But the main change from my point of view is that they now allow the pass house planning package to be used for that modelling method, which is good because we've got quite a few architecture firms that have that skill set in-house now. [Shane Clarke] Okay, cool. Thanks for that, Jason. I've got a question here for you, I think, Peter. Someone's asking, is the flat membrane warm roof, is it trafficable? Is it walkable? [Peter Mills] It's okay for light maintenance traffic. If you're walking on it every day, then it's not acceptable for that. You'd have to put a floating deck on it. Generally, what I find is that if there is a door threshold connected to it, then you need a floating deck. [Shane Clarke] And I guess that's part of Nuralite's offering as well. We have a full code mark certified trafficable walking deck warmer solution if you need one in conjunction with our Neurojax. Yeah, I like this question. Can we use a good polythene to use as a vapour barrier instead of an aluminium foil? [Jason Quinn] You could use a fully adhered vapour tight membrane there, which might include polythene as one of the layers. Right. But I wouldn't just use builders plastic, no. [Shane Clarke] No, no, no, no. I have seen issues on site where joining the lapses is very difficult. And I guess nothing is as airtight or as vapour tight as an aluminium foil layer. [Jason Quinn] It's true, nothing's as vapour tight. There's a lot of fully adhered membranes that would be suitable for that application, but it just depends on the roofing material and everything else. [Shane Clarke] I think that's the reason why your potato chips come in a foil bag now, right? [Peter Mills] Not a plastic one that's taped together. [Shane Clarke] Yeah. Right. Oh yeah, another question here. What does PIR stand for? That is a mouthful. [Peter Mills] That's polyisocyanurate. It's a kind of a foam. It's a foam plastic. That's able to have a closed cell structure and because of that it has a very high thermal performance value. Yeah. That's about all there is to that really. It's got a foil layer to it. [Jason Quinn] Yeah. I mean, you could say it's about twice as good as the white EPS foam in your chilli bin. Yeah. So it's about, yeah, per thickness is about twice as good. It's kind of a good rule of thumb. [Shane Clarke] OK. And one last question here before we move on to the next bit. Can PIR be swapped out in a warm roof for rockwool when we're building above height? Short answer, yes it can. That will give you, it will need to be thicker to achieve the same R value. Also with our roof build up we can actually have a hybrid version as well where we're using a combination of PIR board and Rockwool. So talk to us about that. We can do something specific, yeah. [Peter Mills] The important thing to note is that for walls you can only use PIR for up to 10 metres. But when you're doing a warm roof that same restriction doesn't actually exist. So over 10 metres PIR is OK for a warm roof just because of the level of containment that it has. [Shane Clarke] Sure. OK. Alright. I know we're getting close on time. There's lots and lots of questions here. I can't believe it. So what we'll do is we'll answer all those and they'll be sent back out with the mail out. So just to wrap this up for the end of the year. It feels like the end of the year, that's for sure. It's been a very difficult year and everyone's had their challenges. It is Christmas so we want to give away some goodies here. So what we have typically done this whole year with our webinars is obviously we can't come and see you in the office. So we've turned the $10 per head sausage roll budget into a donation. So because it's Christmas we've upped that to $50 per attendee. So for everyone attending today we're just going to pop up a poll on where you would like your $50 donation to go to. So you've got some choices there from Kids Can, Women's Refuge, Christmas Box, Auckland City Mission or Kiwi Harvest. So we'll just leave it up for a minute or two to let us know where you'd like your $50 to go towards. It says hosts and panellists cannot vote. Oh, we're rough. Yeah, I noticed that. So yeah, by all means pop that in there. OK. Alright, well I think that ends this webinar. Lots of questions for us to go back and answer and we'll come back to you all on. I don't want to take up all of your time, but Jason, thank you very much for being on the panel again. You're welcome and happy holidays. Yeah, likewise. And thanks everyone there for watching. We'll be back next year no doubt with more webinars. Merry Christmas to you all and thanks for viewing. See you guys.