#10 - WUFI, Walls, and Weatherproofing with Villy Yordanov

Jess Kismet (00:00)

Hello and welcome to the Building Sciology Poddie where we talk about better buildings to live and breathe in. My name is Jess Kismet and I am your host. Today I am chatting to Villy Yordanov. Vili is a mechanical engineer who's all about problem solving and improving the world around him.

He has experience in manufacturing and renewable energy and a real passion for sustainability and using his technical skills for good. He absolutely excels in his role as innovation engineer at Pro Clima head office in Sydney. And he has been a fantastic sounding board for me over the last two years with anything related to moisture management in buildings and WUFI. If you don't know what WUFI is, keep listening because we're going to explain what that is.

Villy has most recently been working on solutions for concrete buildings. So we're going to dive into why getting this right is so important across all areas of the construction industry. So welcome Villy. Thanks for joining me.

Villy (00:52)

Thanks Jess, thanks for having me.

Jess Kismet (00:54)

No worries at all. Okay, so as I said, you've been with Pro Clima for two years. ⁓ So how did your, we'll give it, go back a little bit, give the listener a little bit of an idea of where you've come from. So how did your sort of career in building science begin and how did you end up at Pro Clima

Villy (01:10)

Yeah, cool. My journey in building science, I think, began specifically within Pro Clima but my journey within the built environment and sustainability goes back to my uni degree, I would say. So I grew up in Bulgaria, a small country in Eastern Europe, racing dirt bikes. And when I finished school, I had to figure out what to do and decided to go and study engineering in Denmark. And if you are familiar with Denmark,

It was the country, perhaps the pioneer in renewable energy, specifically wind turbines. So just studying and being around the people and the culture, I got exposed to a very interesting mindset about sustainability and renewable energy and stuff. I ended up doing an internship at one of the biggest wind turbine blade manufacturers in Denmark, which was an amazing experience and really ⁓ gained a lot of benefits for my future career as an engineer.

But then decided to move on to Australia to do an exchange semester and haven't moved since. Came here for five months planning to study and married now with two kids and yeah, not going anywhere. But coming here, I moved into solar energy and working for a solar panel manufacturer, solar panels and batteries. So still being all around all this sustainability, renewable energy, wind, solar, et cetera. Then I moved into consulting.

building services consulting in sustainability or what they call ESD, environmentally sustainable design, where perhaps my initial exposure to the building industry began. You're working a lot with national construction code regulations, building projects of all kinds, et cetera, et cetera. And it wasn't until a few years later that someone said, hey, can a client is asking for a high-growth thermal assessment for WUFI.

Can you please write a fee or something? There is a scope for this. And I know that the company I was working for was not keen on doing any of the hydrothermal assessment because of risks, et cetera. But one of the guys said, oh, hydrothermal assessment, talk to Jesse Clark from Pro Clima. I was like, oh, hold on a second. I've heard this name before. Let's check out what this guy is doing. Check, open Jesse's LinkedIn profile. And he just posted a job saying, hey, come work with me, innovation engineer. I read the job description and I'm like,

That's my dream job. I'm going for it. And yeah, a few months later with interviews and everything, I joined Pro Clima and felt like started from scratch deep into the building science thing specifically because yes, even though I spent a few years in consulting within the building industry, that was not as much building science per se as some of you may know. Sustainability is not depending on the company, I imagine, but it's not so closely related to many of the things we talk about when we stay building science like weatherproofing, air tightness, moisture management, et cetera. But yeah, joined Pro Clima about two years ago now, and it's been an incredible experience learning every day and changing the world.

Jess Kismet (04:14)

Mmm.

Yeah, absolutely. So you said that, I just want to clarify, you said that you worked at a solar panel manufacturing? You're talking about like the propeller looking parts of the wind turbines? Yeah, sorry, the wind turbines. Yeah, yeah, yeah, sorry.

Villy (04:38)

Solar panel. ⁓ that's the wind turbines. That's the wind turbines. Yeah,

Vestas. It was one of the biggest until two of our smaller companies joined and they became the biggest. But Vestas was one of the biggest wind turbine manufacturers. There are various sites all over the world making the different parts of the turbines, one being the blades. So each turbine has three blades. So that's where I was working in, new blade manufacturing. But.

There are different factories around the world that work on the tower and the nacelle is what is called the hub that sits at the top where it attaches to the blade and is the actual thing that generates energy. yeah, Vestas is one of the biggest companies this field.

Jess Kismet (05:25)

Yeah, that's crazy. I've seen them being transported like on gigantic road trains. just, they're so huge and so just, they look like they're from outer space. Yeah. So when people think of sustainability, that's, you know, as you said, building science isn't what we typically first think of. We think of solar or, you know, renewable energy and carbon emissions and that sort of thing. So yeah, you're, you're, ⁓

Villy (05:35)

Yeah, that's right. And they keep getting bigger and bigger. It's incredible. Yeah.

Mm-hmm.

Jess Kismet (05:55)

transition into building science with Pro Clima, why was that your dream job? What about it? It appealed to you.

Villy (06:03)

Well, first of all, I get to sit to Jesse Clark shoulder to shoulder every single day. Yeah. Which is the best thing ever. mean, whoever doesn't know Jesse Clark, leading building physicists across Australia. Anytime a question comes in, can freely ask him and learn from him. But yeah, that was one of the main value propositions. Work alongside me, come and break stuff, test things, hands-on experience like...

Jess Kismet (06:06)

Hahaha! ⁓

Villy (06:31)

Yes, I'm an engineer, but as I said, I grew up riding motorbikes up in the forest and you need to learn how to these things yourself to repair stuff when it gets broken. So I do like hands-on stuff, even though I didn't have as much experience specifically building. But yeah, once you have a bit of hands-on stuff, you can figure out the rest. yeah, hands-on things, apply things in practice, not just in the computer world. And yeah, just work for a greater good.

Jess Kismet (07:01)

Yeah, that's awesome. That's awesome. So what does your typical day look like at Pro Clima What are you responsible for? And apart from answering my questions that I fire through to you on a regular basis.

Villy (07:08)

Playing every day. Yeah.

Yeah, it's extremely diverse. My role is called Innovation Engineer so I'm innovating in a way, but it's so broad that I'm doing a lot of things. Of course, it's a lot of problem solving and figuring out how to solve all the problems we're seeing every day in the build industry, especially with both new but also existing homes, small homes, but also large buildings of all kinds.

I do a lot of the compliance related stuff with national construction code when it comes to weatherproofing and condensation management. Also, when you, as a product manufacturer, when you do bring new products onto the market, they need to be tested according to certain standards. So I am the main person responsible to organise these tests, fill in any of the gaps that tests that need to be done when bringing new products in, ensuring compliance of all kinds of standards. But of course.

testing ahead of time, not just for specific properties, but just for the application of the products we tend to use. Figuring out different application of products. mean, Pro Clima is a German based company, German engineered, German made. We bring a lot of the products from there to here to Australia and New Zealand. But many times we have on our hands products that were made for the European type of building, which do not apply in any way to what we do here in Australia. So.

There are times at which we have to figure out how can we actually take some of those products and reuse them in a different way here in Australia for a different application. Or sometimes find a use scenario where there is no such existing product and work with Germany collaborating to formulate a new product and create a gap that is here in the Australian and New Zealand market.

And in addition to all this, WUFI, I do, we're going to talk about WUFI later, I imagine, but WUFI, hygrothermal modelling we are the company that works with the Fraunhofer Institute who has the background of WUFI. So we are the ones who do all the training. So I do a lot of the trainings with professionals, architects, designers, engineers, have all different levels, fundamentals up to advanced, the two dimensional. And yeah, I also go around to sites to advise on our application of our products.

And here and there I do some presentations one-on-one with architects and facade engineers and presenting at larger forums and conferences and expos and stuff. So yeah, extremely diverse and that's why I love it.

Jess Kismet (09:45)

right. So you've got a strong background in engineering. ⁓ How have those skills translated into the work you're doing now in building performance and moisture control?

Villy (09:55)

That's funny you asked this. was thinking about this the other day. I remember my first day of engineering school, we had a guest lecturer that or a guest alumni I would imagine it was who basically introduced to us that said, guys, look, you're going to study four years of engineering and you need to remember from day one that when you finish that degree, you're going to go and start to work in the industry and you're going to use no more than 5 % of what you've studied. So take this into account. Yeah.

And I was thinking about this the other day and I think I am using or utilizing in a way probably 90 % of what I studied in engineering ⁓ as a mechanical engineer. Material science starting from year one, but also thermodynamics, heat transfer, fluid dynamics, air conditioning stuff, which is based on all of the things I had before. Of course, 3D modeling, creating renders and different designs, technical drawings.

main factor in my job, how to read and understand technical drawings. Yes, mechanical drawings are different than architectural drawings, but once you understand one, you can quickly adapt to understand the other. So yeah, when you start studying mechanical engineering, you don't really know, you probably think you're going to go into HVAC here, for example, in Australia, it's quite common, but back in Europe, you imagine you're to start working for a car manufacturer and that's all your scope of work could be. So I would have never thought that

I would end up in the building science field and utilise everything that I've studied almost to a full.

Jess Kismet (11:26)

Wow you must be one of the only people who can say that. Most degrees, most degrees I can imagine, you know, mine included, you don't really, you you learn everything on the job, you get the bit of paper so you can get the job and then you learn on the job. So that's really cool. ⁓ So the work you're doing in WUFI let's actually move on to that because I'm sure the listener wants to know what this weird, weird named thing is.

Villy (11:29)

Yeah, exactly. Probably.

Mm. ⁓

Jess Kismet (11:54)

So could you explain what WUFI is and the connection with the Fraunhofer Institute and how it's integrated into your work?

Villy (12:03)

Yeah, for sure. So WUFI I'm not going to even attempt to pronounce the exact German word of what the four letters stand for, but it's technically meant to say heat and moisture transiency. So if we go one by one, heat, obviously temperature changes, moisture, humidity changes, so moisture changes. And then transiency implies that

this is being simulated on an hourly basis. It's not a steady state condition, one condition inside, one on the outside. And that's it. Transiency means we simulate one hour by hour. So, high growth thermal modeling with simulating moisture and heat movement within assemblies to assess the risks of mould and condensation and long-term water damage that could occur within assemblies, whether that be timber frame or steel frame, rotting, corrosion, et cetera. In a nicely

simply designed software by the Fraunhofer Institute of Building Physics in Germany, which is the creator of this tool back in the nineties or eighties or nineties when they started repurposing or retrofitting a lot of buildings and they had to figure out once you start insulating something that was not insulated before, could that cause new problems? And WUFI was developed and yeah.

Jess Kismet (13:25)

So WUFI was developed directly to solve the problem of insulating old buildings.

Villy (13:31)

That was my initial understanding here.

Jess Kismet (13:33)

Yeah, right. That's interesting.

Villy (13:35)

Yeah. But yeah, Hartwig Kunzel, the godfather of WUFI the creator of WUFI is the man behind. And he's very active in this space to this day, still working for the Fraunhofer Institute of Building Physics. And then yes, Pro Clima in Australia and New Zealand are the official, you can call partner of Fraunhofer for supplying WUFI, technically with licenses and get a kickback from that based on.

trainings and support that we deliver to the market.

Jess Kismet (14:05)

Mm-hmm. Mm-hmm. I actually met Hartwig before I really knew who he was. Jesse got him to the building physics conference. I think it might have even been the very first one I ever went to. Yeah, so I actually, pardon? Yeah, he came over to Australia and he was one of the speakers. And I wish I'd understood more of who he was and his work because I would have...

Villy (14:18)

yeah, an AIRAH building physics conference. Yeah. AIRAH building physics. Yeah. Yeah.

Jess Kismet (14:33)

Yeah, I didn't really I was I was this is in 2018. And I'd been in the energy efficiency game for a while. But that that conference was the beginning of my sort of journey into the building science field specifically, building performance field that was like a, you know, opening of the doors for me that particular event and he was there. So yeah, pretty, pretty, pretty

Villy (14:45)

Hmm. Amazing, yeah.

Yeah, pretty cool. Yeah, I know he did present not last year, the year before, but yeah, didn't manage to come in person, it was all online, Yeah.

Jess Kismet (15:06)

Yeah, yeah, yeah, it can be hard to get them all the way over here. ⁓ So it's a hygrothermal, so heat and moisture, and it predicts a mould index, right? So it gives us an idea of what the risk of mould appearing in a particular area of a building. So it doesn't assess, I often get asked if WUFI assesses a building as a whole, like, will my building go mouldy

Villy (15:10)

Hmm.

Jess Kismet (15:35)

And it's not really for that, it?

Villy (15:38)

Well, there is a software called WUFI Plus, which you can do a whole building modeling, but you would not really do it to answer that specific question. Would my whole building go mouldy You would focus on risk areas in a conservative manner. You would grab certain one-dimensional sections of a wall, of a roof or a slab if you're going to have, if it's worth simulating, if it's a complex scenario.

And yes, depends on how deep you want to go and how unique and perhaps different your design is to what the industry is used to seeing and knowing what works in practice. Perhaps utilise a two dimensional calculations across slab edges, window junctions, wall to roof connections, et cetera, where you have a change in a geometrical shape where two surfaces at different angles meet and two different materials meet at different angles.

that could create potential issues from moisture accumulation or thermal bridging, cold spots, et cetera. But to answer the question, would your whole building go mouldy? I don't think it's a very easy, straight away answer.

Jess Kismet (16:46)

No, no, I think it's just a misconception in the sort of industry that people think that that's what they're going to get out of that assessment. But no, it's the most common WUFI assessments, the ones that I do, are the 1D and they are simply of one build up, one wall system, one floor system, one roof system. I've tried to do the 2D and I only had the license for one year. I think I only really did one job with it. ⁓ Do you think that there is...

that the 1D simulations can cover most scenarios with sort of safety, like safely make an assessment.

Villy (17:22)

It depends. Actually, that's how we begin our two-dimensional course talking about when would you even go for 2D and when is 1D insufficient. And one of the first examples we give is take a section or a plan view of a typical stud wall. If you are to simulate a stud wall one dimensionally through the insulation there compared to one dimensionally through the timber layer or the steel stud layer compared to

one, two-dimensionally across the whole assembly, you would find sometimes that the simulating it through the installation layer is the most conservative scenario and a one-dimensional simulation gives the same results as two-dimensional, which leads you to understand that 1D is sufficient. You don't need to go to 2D. Then you start overlaying a scenario where you add an additional layer of installation on the outside or an additional layer of installation on the inside within the service cavity.

Villy (18:19)

And in that case, your frame structure is either on the warm side or on the code side. And you start seeing that the difference between 1 and 2D becomes apparent in some of these cases. Then you apply this to more complex junctions like a slab where an insulated slab edge cannot be taken into account into ⁓ a 1D scenario. And then the answer is that 1D is never going to be enough for that specific junction.

So yeah, for the most part, the typical wall constructions that we use in 1D through the insulation layer is the most conservative way you can do things. But once you get into the junctions and the complex sites, 2D is a better tool to use.

Jess Kismet (19:03)

Okay, the license is a little more expensive though. I think it's, you know, for a practitioner, I think it's double the price of a 1D license. So yeah, you know, in a

Villy (19:10)

Yeah. Yeah. Yeah. But the license, of course, the license is going to be expensive, more expensive because it's a lot more complex too. It's a very different way of calculating. the more, the bigger implication to someone like a consultant who's going to be using this tool is the computational time, especially in the latest version of WUFI 7, a 10 year calculation of a typical wall assembly can take a minute, a typical three to five year.

Jess Kismet (19:18)

Yeah.

Villy (19:40)

two-dimensional simulation, it's upwards of 10 hours. So yes, you normally run overnight unless you have really, really powerful computing power. But yeah, so because of this, you can run 10, 20 different iterations to advise your client on various options of installation thickness, location, type of membrane inside, outside, et cetera. You can't afford to do this on a two-dimensional scenario. You, you are just going to run out of time. Yes.

Jess Kismet (19:44)

Yeah, I left mine going overnight several times. And yeah. Yeah.

No.

Yeah. Yeah. It'll get expensive really, really fast. 100%. simulations.

Villy (20:12)

Yeah.

The bottom line is that at the minute there is no one forcing you to do 2D instead of 1D to meet compliance with the building code. So for the most part, if you do want to follow the performance method and use the verification pathway of performing a hygrothermal simulation in WUFI a 1D simulation is technically sufficient to meet building code.

Jess Kismet (20:20)

Yeah.

Yep. So to clarify what Villy is talking about, is the WUFI can be used as a verification method ⁓ or an alternative performance solution in the condensation management section of the building code. ⁓ you can do, for example, in a wall buildup, you can use a certain type of membrane, depending on your climate zone. Or you can do if you don't have a wall buildup where you can use a membrane or you don't want to use a membrane.

you can do a WUFI simulation instead and prove that your wall system won't go mouldy at the critical point. So it's just sort of a flexibility the building code offers now.

Villy (21:12)

Exactly.

Jess Kismet (21:15)

Something where a homeowner can say, this clause, you said that this building wouldn't go mouldy because you did this and it did go mouldy. So this is your fault or someone's fault.

Villy (21:28)

Yeah, okay, so you need to look at what the objective and the performance requirement of the specific clauses in the condensation management provision specifically. It does state that anything that's going to have an impact on the health of occupants or loss of amenity. So yes, if mould of the does occur, technically the objective of that clause has been breached.

and someone needs to be held liable for, and then it begins the discussion, who is liable? Was it the designer who put it this way? Was it the architect? Was it the consultant who said it's going to be that way, but it ended up being otherwise? Or was it the builder that didn't install the things well, the way that the designer specified that they should have been? And that's where things get tricky and yeah.

Jess Kismet (21:59)

Mmm.

It gets complicated and that clause hasn't been used yet. And until it does, we won't really have any precedent. But it's, I think it's enough of an indicator that the legalities, like the legal requirements are closing in around building health and building performance in a way that is no longer something that can be ignored, would you agree? Yeah, yeah.

Villy (22:21)

No. Yeah.

Yeah, absolutely.

Jess Kismet (22:45)

Okay, concrete. Oosh So you've developed a real specialty since you've been a Pro Clima in moisture management in concrete structures. I know that, you know, we know that concrete is has a really, really high percentage of water when it's poured and then some of that evaporates over time. it's concrete holds a lot of moisture in it inherently, because of the way it's made.

Villy (22:47)

Okay. 

Mm-hmm.

Jess Kismet (23:15)

So what have you learnt about concrete and what is it that makes concrete such a unique challenge?

Villy (23:22)

Yeah, you're right. One of the main things about concrete is that what Joe Lstiburek describes as a moisture reservoir, it stores a lot of moisture within its pores. But that may not necessarily be an issue if you have allowed it to evaporate ahead of time and cure sufficiently. What the biggest challenge with the typical precast concrete construction, and that also applies to in situ concrete, but also all the permanent formwork solutions we are seeing pop out.

Jess Kismet (23:30)

Yes.

Villy (23:53)

left, and center in buildings where you have a sandwich of few panels, for example, fiber cement panels and you pour the concrete in between and you leave it as it is. The issues with these type of assemblies is the material properties of the concrete in general and specifically how air and also vapour impermeable concrete is. There is no drain and ventilated cavity in a face sealed concrete assembly.

Jess Kismet (24:00)

Mm-hmm.

Villy (24:18)

So when you have a lot of hot humid air from the indoor environment trying to escape through the building envelope towards the cold, colder side, towards the outside in winter, you have vapour passing through the plasterboard lining, passing through the insulation layer and get in contact with a cold surface of the concrete and has nowhere to go. There is no drain and ventilated cavity. The concrete is highly vapour impermeable. And when hot humid air gets in contact with cold surface,

Not good things happen. And this is where we see the condensation on the inside face of an interiorly insulated concrete being a very big issue in our industry.

Jess Kismet (24:50)

Hmm

Do you have any photos of this?

Villy (25:02)

Yes?

Jess Kismet (25:04)

Are you willing to share them? Yeah.

Villy (25:05)

Yes, I do have a photo even from my building physics conference preso from AIRAH that had mould image on a concrete building in Canberra. I can obtain a few more from a few engineers who have been sharing some horror stories lately, talking about the amount of moisture condensing on the concrete and draining down into the slab, leaking through the bottom plate of the stud wall into the plasterboard wetting the carpet of the indoor space. Yeah, liters of water. Yeah.

Jess Kismet (25:36)

I can imagine. I can imagine the mess. Yeah,

Yep I've been made aware of a project being worked on by a colleague of mine recently where they've just created concrete bunkers here in Adelaide. So ⁓ not climate zone six, but climate zone five. So it gets cold enough during winter. Yeah, and they've just created these concrete bunkers and they're set into the ground as well. So they're retaining walls.

Villy (25:55)

It's cold enough, yeah.

Jess Kismet (26:04)

So there's just nowhere for the moisture to go at all. Obviously that's waterproofed on one side, you know, habitable spaces inside concrete bunkers inside the earth. I sort of, I just, I was sort of talking about this with my colleague and just like, ⁓ my goodness. I mean, will that earth keep that concrete warm do you think in that situation?

Villy (26:28)

I don't think so. It will keep it where the slab is. That's why many passive houses get away without any floor insulation where slab is sufficient, but not on the walls. If anything, if things are not done well, you can promote further movement of rising damp through the concrete, wetting it continuously through groundwater.

Jess Kismet (26:30)

No?

Yeah.

And how do we go about solving this issue?

Villy (26:54)

Yeah, complex, complex question. And many people don't like to hear the answer. The ultimate solution is... Drum roll, please. Put all the insulation on the outside. Put all the insulation on the outside. Keep that concrete warm. Utilise the thermal mass the way it was meant to be utilised in the first place. And yeah, keep the concrete warm. Hot humid air is not getting in contact with the cold surface. Chances of condensation are...

Jess Kismet (27:08)

Yeah.

Villy (27:24)

almost fully eliminated depending on climate zone. But yeah, much, much better design approach. The only way a concrete building could be built anywhere in Europe, for example. But why do people don't like this? Or why do architects and developers and designers don't like this? You hide the concrete look, which is the first thing behind going for concrete in the first place. Yeah, you're going to cover it with an exterior grade insulation to keep it warm. You can put some sort of

cladding on the outside, perhaps cladding that looks similar to concrete, but then you can ask yourself the question, why concrete in the first place? You could have done exactly the same thing with a lightweight steel frame or timber frame if you wanted to do this on a resi (residential) scenario. So that's the ultimate solution. Other solutions. That's the other idea. Yeah. That's the other reason why people are going for panlised concrete, pre-class concrete panels. It's much quicker to install for sure. Yeah.

Jess Kismet (27:58)

Why? Yeah.

It's also quicker, right? Concrete, mean, yeah.

Villy (28:18)

But yeah, so what's the other solution? Put on vapour impermeable insulation on the inside face of the concrete. This is normally a closed cell expanded or extruded polystyrene, which is a vapour barrier. So you don't allow the vapour to get in contact with the cold surface. You'd stop it at the insulation layer. Of course, you need to tape each of these boards with the vapour barrier tape. There is one problem with this. It's combustible.

Villy (28:46)

you can't install it in buildings higher than 10 meters high in a commercial scenario. If you really want to build a house out of concrete, you can do this in a single dwelling house, but anything high-rise, no go without a specific engineering, fire engineering solution. And the last option, which is what we as Pro Clima have been trying to figure out and how we can solve this issue without going to the externally insulated extreme is putting a vapour control layer on the inside of the installation there. This is the Intello Plus intelligent air barrier, where the idea is you do stop the vapour going through the membrane in winter so that the vapour behaves as a vapour barrier in the colder months where humidity indoors tends to stay low. So you don't allow that much vapour to pass through the installation there getting in contact with the concrete. But then in the hotter, humid months,

Jess Kismet (29:22)

Mm-hmm. Mm-hmm.

Villy (29:45)

especially if you do have some moisture within the concrete that's being pushed inwards. Again, from hot to cold, you go from outside towards the inside in summer in terms of vapour drive. The membrane opens up, becomes highly vapour permeable, and it allows that vapour to diffuse to the indoor environment so that it prevents it condensing within the wall assembly. And yeah, this is a solution we've been doing a lot of work in the background.

Jess Kismet (29:51)

Yeah.

Villy (30:13)

trying to figure out which climate zones it's going to be a suitable design approach to do and what can be done about it so that people don't have more than their wall assemblies, but still keep their concrete where it is.

Well, simple on paper, but once the practical side comes into play, you need to know what you're doing. You need to plan well ahead of time and you need to do a good job installing that membrane in order to be doing its job as intended. Because the membrane will behave as a vapour control layer as long as it's a nice and airtight install. Yeah, exactly.

Jess Kismet (30:45)

Yeah.

Mm.

Yeah, yeah, yeah, yeah, that makes sense. And all of this advice that you're giving, you mentioned climate zones before. So externally insulating concrete or internally insulating concrete, is there one that's better in the warmer climates or colder climates?

Villy (31:17)

From a lot of the hygrothermal simulations we've done for this specific scenario, I've seen that Brisbane specifically is okay, solely from the purposes of reaching national construction code compliance for its mode index. It seems like for internally insulating concrete, ⁓ yes, because it doesn't get cold enough. The concrete doesn't get cold enough to the point that condensation forms for too long.

Jess Kismet (31:33)

for externally insulating internally.

Mm-hmm.

Villy (31:46)

And yeah, Brisbane seems to be okay. Anywhere, Brisbane and anything north of Brisbane basically. Anywhere south from that, including Perth, where we see not so cold winters and relatively dry weather. Even in Perth, we see a lot of issues with internally insulated concrete. But yeah, where does external insulation begins to work? Well, technically again, Joe's Lstiburek's perfect wall. Put all your thermal, air.

Jess Kismet (31:52)

Okay.

Villy (32:15)

water and vapour controllers on the outside of your assembly and you can put that assembly anywhere and it's gonna work. Yeah.

Jess Kismet (32:22)

Whatever you want with it. yep.

Took me quite a while to understand that perfect wall, you know, all the different layers and why that, you know, because in Australia we put all sorts of layers on all sorts of places in the frame, insulation in the frame, and when I did understand it, it just...

Villy (32:27)

Hmm. Yeah, good.

It clicked in it. Yeah. Yeah, exactly. It makes sense. Why don't we build it like that? Why don't we build it like that? If it does make so much sense. Yeah. It's a big issue. Biggest question. Yeah.

Jess Kismet (32:43)

It makes sense. Keep the structure warm for goodness sake. That's all you got to do. Pardon? Why? I know.

Jess Kismet (32:56)

So the perfect wall, I'll put a picture of what we're talking about on the screen so people can see what we're talking about, but.

You've got all the layers on the outside of the frame. Can you still insulate inside the stud frame?

Villy (33:08)

Sure, you can. You have a lot of hollow space there that you can fill in with insulation and might as well utilise it. But what I recently, for example, talked to some of the North Americans at the recent Building Science Summit in New Zealand, they said they stopped putting any of the fibrous cheap insulation between the studs. Everything sits on the outside as a perfect wall. I said, why? I said, well, it's a waste of time. You have such a high thermal highway through those two studs that much insulation as you put in between, lose a lot of the effectiveness due to thermal bridging. So might as well not waste your money and time and just put everything on the outside. Which is ironic to hear, given that that's all we do here in Australia on a 90mm frame. Yeah. But if you take Germany, for example, you would still find a typical lightweight structure with timber. I don't think you'll see steel frame there like that.

Jess Kismet (33:51)

I know.

Villy (34:02)

But timber frame in a typical residential scenario, much thicker walls, not 90 or not 140, much thicker walls filled with fibrous insulation and external insulation as well. So they have a certain guidance as to how much is in between the studs versus how much on the outside of the studs. It's a safe scenario for a condensation point of view. But yeah, they certainly utilise those really big studs that they have to fill them in with high quality fibrous insulation.

Jess Kismet (34:30)

How big are they? How thick?

Villy (34:32)

Well, I don't want to quote the German carpenters here, but upwards of 200 mm it's thick walls, thick, big, solid stable structures. could, I mean, talk to any German or European, as a matter of fact, coming into Australia and seeing a 90 mm spring ⁓ erected into a building site. They're like, is this an internal wall or what? Even internal walls could be somewhere quite thick, yeah.

Jess Kismet (34:43)

All right.

Ha yeah, don't, anyone who comes from overseas to Australia comes here and goes, what the hell, what the heck is this? What are you doing here? And I guess we just take it for granted.

Villy (35:09)

Hmm.

Hmm.

Jess Kismet (35:15)

In your experience, what are some of the most common misconceptions about moisture in buildings?

Villy (35:21)

Moisture in buildings. Okay. Common misconceptions. Here is an interesting one that I keep saying every single day. And it took me a while to get what was happening until I realized that people are completely confused. When people see the magic line of hope, annotating the pliable building membrane that sits on the outside of a building. And if you ask many of people, what is this? What do you put this membrane there for?

Many times the answer is, oh, you put it for condensation, to stop condensation. I find this as a big misconception in the industry. The pliable building membrane that goes on the outside of the structure is not to stop condensation. It's for weather protection. It's called a weather resistive barrier because it resists the weather. The risks of condensations are much, much lower compared to what we used to use there being

shiny aluminum foil, the perfect vapour barrier where condensation will definitely form. But this membrane is not installed on the outside of the structure to stop condensation. It's installed to protect the structure from getting wet in the first place, which is your main priority. The main priority is you want to stop water ingress from the outside. Priority of 1000. Priority of 100, Passivhaus style principles.

Priority of 100 is your air tightness layer. Prevent accidental air leakage, improve energy efficiency, energy leaks, moisture leaks, ⁓ keep your structure airtight. Basically prevent the effects from wind washing from the outside to affect your insulation effectiveness. And then vapour diffusion and the risks of condensation comes next. But.

Jess Kismet (37:12)

Yeah, I agree with you. I think that is one of the biggest misconceptions because the reason that we introduced or the reason that the industry uses these membranes in the first place is to protect the frame from the weather during construction. That was why they were introduced and it became a problem because we were using foils that was trapping vapour. So that is why the requirements for vapour permeability of these membranes has become an issue.

the whole purpose is, as you said, to protect the frame from the weather. And that is why when you see torn ripped membranes, you know, in developments or on a construction site, it's a complete waste of time.

Villy (37:50)

Yeah, you might as well not have put it. Yeah. Exactly. Yeah. And.

Jess Kismet (37:52)

You might as well not have put it there because it's doing absolutely nothing. Investing in a good quality membrane and proper install is the only way that's even worthwhile doing.

Villy (38:01)

Yeah, exactly. And just to clarify, yes, of course, it's a main priority to protect your structure during construction, because that's when it's going to be the most vulnerable before any cladding or before any roof structure is go over it. But you also want to keep your structure dry during occupancy for the next 50, 100 year of whatever your planned building life is. And even though you may have protected your structure well during construction, you don't want to remove this protection once the building is fully cladded over.

Because water will find its way through. There is enough studies to show that rain under wind driven situations, what we call wind driven rain, will find its way past the cladding. And it's going to try to get into the interior, wetting the structure and causing long term damage if not attended to on time.

Jess Kismet (38:51)

Yeah, yeah, definitely. that's usually I did a post just recently, was a quote from Joe Lstiburek himself, we've been mentioned a few times today. ⁓ A quote from him, "Repeat after me, all claddings leak" At some point, they're going to leak, whether it's through the joins, whether it's window openings, you know, through they just eventually over the life of the building, water ingress will happen.

Villy (39:05)

Yeah.  Hmm. I think the quote was about windows. It says that two types of windows, those that leak and those that will leak. That's it. Same with the cladding. Yeah.

Jess Kismet (39:26)

Yeah, that's another one.

Yeah, yeah, yeah. So, you know, water is not good for buildings and the membrane is a crucial, crucial part of protecting the structure and the durability of that structure. So, yeah, good one. Good tip there, Villy.

Villy (39:34)

No.

Yep, absolutely.

Hmm.

Jess Kismet (39:50)

How do you approach balancing air tightness and vapour control, especially in our warm humid Australian climates up north?

Villy (39:59)

Do the perfect wall, end of story. yeah, the thing is it's quite challenging. And yes, while we do have many off the shelf solutions that people are going for, I think it's really a case by case basis, depend really, of course, mainly climate dependent, but not just because you're in climate zone five and not six or whatever. Also microclimate, like are you on a hill? Is it a wind driven rain? Where is the wind predominantly coming from? Like these are things that ideally, someone should take into account early on when planning the building for optimal, healthy, durable, energy efficient performance of your buildings. But from there, we have varying climates in terms of how cold they get in winter and how humid they get in summer. And dealing with this is not a straightforward off the shelf solution for every situation. So it's really case by case basis and we try to help as much as possible.

based on where the climates are and the type of construction that's being utilized, but very challenging for sure.

Jess Kismet (41:04)

I thought you said the perfect wall was the solution. Off the shelf solution.

Villy (41:07)

The perfect wall is the solution. It's just not an easy sell for most people. cause the walls gets thicker. The installation that goes on the outside is not cheap. The way you hold your cladding, whatever you want to be on the outside needs to be carefully planned ahead of time to how you're to hang it off that far away from your structure. ⁓ because you have such a big installation sitting in between how you're going to transition from your wall to your roof without interrupting your rafters passing through all these things are doable, we know how to do them, but they're not standard details to what architects are used to.

Jess Kismet (41:43)

Yeah, it's a big education piece. Getting them to detail vapour permeable membranes correctly is challenging enough.

Jess Kismet (41:53)

On the upside though, I have been doing some talks to uni students lately. So this sort of stuff is making its way into unis now, which is positive. And your comments earlier about actually using your uni degree, I'm hoping that this sort of stuff will start to be integrated into architecture degrees and construction management degrees as well so that these up and coming site managers and architects can use what they, some of what they learned at uni as well.

Villy (41:59)

Amazing.  Like it's done overseas as well. I'm pretty sure many of the architects overseas study this building science principles in great detail. Not just the fancy aesthetic stuff.

Jess Kismet (42:34)

Well, to me, it's not, you know, it's not.

Yeah, yeah, it's it's not if you're building a building, you're dealing with heat, air and moisture, no matter whether you know you are or not. So it's all it's not it's not. It's just building. It's not it's not building. I mean, it is building science, but it's also just building. Understanding this stuff is fairly important to understanding construction in general.

Villy (42:54)

Hmm.

Yeah. Exactly.

Jess Kismet (43:00)

Have you had a particular case study or project that really highlighted the importance of getting moisture management right? Have you had lessons learned? Stuff up.

Villy (43:12)

Hm I wouldn't say a particular project. A couple of things spring in my mind straight away. Obviously lessons learned from all over the world over the last few decades. The leaky condo crisis in North America and the New Zealand leaky building crisis that cost many, many billions of dollars in damages and health implications to occupants is well documented and can't be emphasised enough how important it is to sort this water ingress out from the structure early on. But what I also come to mind is all the cross-laminated timber buildings that come every now and then lately popping out on projects targeting low embodied carbon emissions and all these kind of sustainability initiatives.

Well, timber is great until it gets wet for too long. So these type of buildings, we need to make sure that they stay protected all the time from the factory up until the building is fully occupied. And we see some not so perfect approaches for this on site on some of these timber buildings where protection was not done on time or not done at all. And you may survive one rain event and after the second, you're in big trouble and all… the carbon emissions you thought you've saved because you've used a lot less carbon intensive material being timber compared to steel and concrete will get completely blown out of the water when you draw the line and see how much energy and chemicals you had to use to dry that timber and clean some of the stuff that happened to the timber that you didn't want to happen.

Jess Kismet (45:03)

Potentially replace some of it, right?

Villy (45:05)

That's a big, job and probably a lot more cost, but yeah, you don't want to go there. And if you speak to any person dealing with mass timber structures, they are becoming more more wary and aware of the consequences and they do anything about it to anything that in their power that they can stop it.

Jess Kismet (45:07)

No.

Yeah, right. So timbers treated though, right? The timber that they use is not just raw timber. It's been impregnated with something or it's been, you know, in the, I'm actually reading Rottenomics. You mentioned the leaky building crisis in New Zealand. I'm currently reading the Rottenomics book and they, I'm learning a lot actually about, you know, history because it's kind of closely linked to Australia as well, like the history of construction in New Zealand. So it's quite relevant.

Villy (45:36)

Thank you.

Mm-hmm.

Jess Kismet (45:52)

I'm sort of learning about some political decisions and things that led to this milking building crisis, as well as industry and regulatory decisions that were made. And ⁓ one of them was how the timber was treated and what types of timber they used. So in the mass timber industry, is there a certain type of timber or a certain type of treatment that is only allowed? Is it you're aware of?

Villy (46:08)

Yeah.

I am not an expert and I don't know these things. I know that Germany has moved years ago into fully untreated timber. So the argument is timber begins to rot, mould begins to grow if you give it the right conditions of moisture and food source. If you keep everything dry, these things should not happen. So the approach is protect. Yeah, exactly. Protect everything ahead of time in the factory. And once you build, build and the...

Jess Kismet (46:27)

Really?

Yeah, okay. So they've perfected the art of keeping it dry.

Villy (46:47)

big tents and teepees and the second rain drops you clean it straight away or you squeegee it out of the building. You have floor drains positioned every so often across every floor plate so that no water gets in contact with the timber because yeah not good things will happen.

Jess Kismet (46:48)

Yeah, yeah.

Yeah.

Yeah, so they're choosing to keep the chemicals out of the timber and choosing to be proactive about how dry they keep it instead. Yeah, wow, that's really interesting. Yeah.

Villy (47:13)

Exactly, yes. It's a hard sell for the tropics, if you're to have constantly exposed high humidity environment and also termites. You do want to do something about that, but that's a different topic. And again, not something I'm an expert in, but all kinds of opinions there.

Jess Kismet (47:26)

Mm.

Yeah, I'm interested in digging into that a little bit more deeply at the moment. So if anyone, ⁓ if you're listening and you know you have experience in the timber industry, send us an email or a comment on this podcast, I'd love to talk to you. What trends or innovations are you seeing in the building science space that you are particularly excited about?

Villy (47:38)

Yeah.

I think we're starting to move into the right direction. We start to see facade engineers specifically for high-rise projects where you do deal with lot of high wind pressures and weatherproofing is front of mind as ⁓ again, first order of priority, stop the water coming in. And people are realizing that in these high wind environments, flexible membranes are not enough.

They flex in and out of the building. You don't know how long the fixing points will last, and you need to move into a rigid board solution of some description, protected as well, either taped at the joints or ideally fully protected with an adhesive membrane. So we are seeing the push towards state-of-the-art rigid board solutions and in some applications with exterior installation on the outside.

It's going to take a while to become a common practice, but we are starting to see projects pop up and yeah, we hope we see this move into the right direction in the future.

Jess Kismet (49:02)

So you're seeing this move more into the commercial space, not just into the resident, not just coming from the residential space. Is that what you mean?

Villy (49:10)

Yeah, definitely in the commercial because there's a lot of exposure we have in there, but in the residential space a lot. mean, the Passivhaus movement has gained quite a bit of momentum. We see a lot of Passivhaus projects coming up ⁓ following full design principles on weatherproofing and air tightness and vapour control, which is incredible to see. But we start seeing also a lot of rigid board solutions on the outside, but sometimes also on the inside.

that originally used for bracing are now applicable also for high wind zone pressure weatherproofing systems and air tightness.

Jess Kismet (49:47)

So could you, for the listener who doesn't understand what you're talking about, could you explain a bit about what you mean? About the rigid boards

Villy (49:52)

Yeah, so when you have a typical lightweight construction where your structure is comprised of timber or steel framing members, you have options how to protect it on the outside. Normally you staple onto the timber or you screw onto the steel, a typical pliable building membrane, which ideally should be stored nice and taut and well, but wind will blow onto that building.

When the wind blows towards the wall, the membrane will bulge inwards, basically compressing the insulation that's in between the studs. When the wind blows from the other side, the membrane will bulge out from the building, perhaps minimizing the gap between the cavity or getting in contact with your cladding or your bricks or whatever is in front of it. And this happens millions and millions of cycles over the lifetime of the building, the membrane going in and out like a parachute.

And there is no long-term studies or any tests that could prove how long a typical pliable membrane lasts in high wind exposure environments. And that's why many jurisdictions actually have reinforced overseas the use of a rigid substrate. That could be an oriented strand board or plywood in the residential context. But that's combustible. It can be used in high-rise

applications here in Australia. So we move to a non-combustible solution such as fiber cement boards or exterior grade gypsum boards. So you put those boards on the outside of the structure and then you need to protect them at least at every joint where the panels meet each other, but perhaps fully protected with an adhesive membrane fully throughout so that if any water comes in the structure, the boards and the framings are protected.

But when wind blows, the board does not deflect in and out like a parachute. ⁓ the connection points and any compromised points at which water can find its way through the building are greatly improved.

Jess Kismet (51:56)

Mm hmm. Yep. And that plyboard or OSB, two questions. Do you have a ⁓ preference or an opinion on which one is better from a moisture control perspective? And two, how does that change the vapour permeability of the wall system? Because obviously the membrane and that substrate are going to behave differently to a pliable membrane.

Villy (52:20)

Yeah, so these two questions actually quite interlinked together. So how much would the vapour permeance of the full assembly will change when you start introducing a board? Will it depend on the property of those boards? And do I prefer ply or OSB? I don't know because I don't have a very clear picture on the material properties of these materials in Australian context. We know that in general, oriented strand board three (OSB3) tends to be a lot more vapour permeable than most plywood.

and more permeable than OSB4 just because of the types of adhesive used. But the type of timber and the types of adhesive used between the different veneer levels of layers of plywood could determine how permeable the plywood itself can be too. So I do not have a preference from my side and that's not something I could enforce as a product supplier of membranes. But yeah, the ultimate goal is that we're going to get some material data of Australian made OSB and plywood boards. But in general, once you start introducing a rigid substrate and adhesive membranes into the structure, you start adding vapour resistance. And again, going back to concrete, when you have a layer that sits on the cold side of the installation that vapour can't freely escape through, you may have risks of moisture being trapped on the backside of that ⁓ rigid board system. And if left for too long, mould could start grow, rotting may begin. And these are the type of system where you do one thing, you do install the board for long-term durability from wind exposure and also bracing elements, structural stability, et cetera. But then you start questioning condensation risks and then brings into the question, well, how do you solve this? Either vapour controller on the inside and or an external insulation there on the outside to keep that board warm. Again. both residential and commercial, same application.

Jess Kismet (54:14)

Yeah, okay.

So moisture management comes down to basically keeping the external layers warm or stopping moisture from getting to the external layers. In a nutshell. So I did the building science fundamental course with the illustrious Dr. Joe Lstiburek earlier in the year. And he says that ply is better because ply as it gets wetter gets more vapour permeable. So this confused me because I had heard that

Villy (54:25)

That's it.

Mm-hmm.

Jess Kismet (54:46)

without some, you you said there's not a lot of data in Australia. So we do need some more reliable data. ⁓ But I had heard just that OSB was actually better than ply. Ply was going to go mouldy a lot more quickly. So that was sort of that was the information I had. And then I heard Joe Lstiburek say that that ply was actually better.

So I was questioning this and then I was told that the glue layers and the chemical makeup of ply in America is different to Australia. So this has been a bit of a confusion amongst some people I have spoken to. Do you have anything to add to that?

Villy (55:21)

Mm-hmm.

This is not an easy topic, but a hundred percent, there is so much variance in the type of timber, but the type of adhesive that's within those type of materials. In general, when timber gets wet, it becomes more vapour permeables. The fibers open up and allow the movement of vapour to move freely through. So how much timber is in ply compared to how much timber is in OSB? Many times OSB has a lot of glue.  some of what they learned at uni as well.  In addition to timber. So that glue would really determine what's going to happen once stuff gets wet. But to make things even more complex, the vapour permeability of timber changes based on the history of timber wetting. If you've had many cycles of how often that timber got wet and dried and wet and dried, and you keep testing the vapour permeability, you're to get different answers. And this brings big unknowns as to what's happening. How long is the ply that you're about to put in your building bbeen in the warehouse, gone through a few winters of really dry weather and a few summers of extremely high humidity and just by simply sitting in the warehouse got wet and got dried just to try to equalise the levels of moisture within. But on average, yeah, you expect that timber does get more permeable when it gets wet and the type of adhesive will change this.

Jess Kismet (56:44)

Okay.

So this is another example of how computer simulations and reality don't always line up because we put OSB or plywood into a WUFI simulation and we base our simulations on the properties inside that software. But actually in reality, material that we use could be quite different. The material that gets installed could be quite different just because of how old it is or how many times it's got wet. Would you say that's true?

Villy (57:04)

Mm-hmm.

Mm-hmm.

That's true.

Yeah, absolutely.

Jess Kismet (57:19)

Yeah, right. That's interesting.

Villy (57:21)

That's why you make conservative assumptions that and you validate studies from various material sources and in like real life experiments, which Fraunhofer has done to validate the needs, the how closely computer simulations correlate to reality. And many times whether even though, yes, there are variations in reality, they are not.

Jess Kismet (57:41)

Hmm.

Villy (57:48)

so significant to the point that you're going to get a completely different result from your calculation. But yeah, in general, calculations are never perfect.

Jess Kismet (57:55)

Mm-hmm. Okay.  Yeah, yeah, but you have a fair faith in the ability of WUFI to make good conservative assumptions based, mean, rubbish in rubbish out, right? So, you know, the person doing the assessment has to understand what they're doing. But if they do understand what they're doing, you're feeling fairly confident in the simulations.

Villy (58:15)

Yeah, yeah for sure.

Jess Kismet (58:21)

For the engineers and designers who want to understand more about this stuff and level up ⁓ their training, where do you recommend they start?

Villy (58:30)

Honestly, go and read the Pro Clima study on air tightness and moisture management in buildings. It is not a small book. It is half a physics textbook and half a practical guide on how to do stuff. It's going to take you a while to go through, but you're going to learn a lot. And if you don't want to spend all that time, go and watch two YouTube videos, which are the summary of that study. One by Jesse Clark, one of the main authors of the study and one by

our German master carpenter Daniel Jakobs talking about the practical side where we did a road show of this study and they presented and we did the recording and it's now on YouTube. two videos, 40 to 50 minutes each can get a good glimpse of this. If that's not enough, proclima.com.au/technicalcorner and go and read all the articles there. Come and do some WUFI training with us. If you want to learn more about woofie and how to use it, how to apply it in your job. And if you ran out of this.

Go and ask Jess about Joe Stiburek's courses and articles and Rottenomics books. Yeah.

Jess Kismet (59:34)

Yeah, Joe Lstiburek Yeah, yeah, that's where you go from there. That's it. That's absolutely it. Yeah, highly recommend. Again, all of those links will be in the show notes. So please, if you're interested in learning more about moisture management in hygrothermal analysis in anything to do with Pro Clima membranes, moisture management, air tightness, weather proofing, weather control, all those sorts of things, please look at the show notes. There'll be some really good and relevant links there.

Villy (59:39)

Yeah.

Jess Kismet (1:00:02)

Final question, really. I asked this question of everybody. What is the one thing that you want people, the person listening, what is the one thing you want them to know?

Villy (1:00:16)

I've listened to all your episodes, so I knew you're going to ask me this. And here is what I think I want to say.  Be aware that when trying to solve one problem, you may be creating another. We learned this the bad way when we started putting insulation into our buildings to make our buildings more energy efficient. And then we realized that when they put insulation, some things stay colder than others. And that's when condensation happens. So view you're building holistically, whether you're an architect, designer, engineer, or builder, and question, if I make a change here, could that lead to a change elsewhere? And if you don't know the answer, try to ask people that may know the answer. We've learned, we've had lots of years of experience and we've learned from many years of failures that we don't need to repeat again.

Jess Kismet (1:01:12)

100 % over, you know, unintended consequences and they can bite you on the bite and there's lots of overseas lessons that we can learn.

Villy (1:01:18)

Mm-hmm.

Jess Kismet (1:01:27)

So, all right, really, we will wrap up this conversation there. Thank you so much for joining me. I really appreciate your time and your expertise.

Villy (1:01:27)

Yep, absolutely.

Thank you so much, Jess. Pleasure to have you.

Jess Kismet (1:01:45)

All right.