April 12, 2022

EnerPHit - Passive House Retrofit, Air tightness and Ventilation - Es Tresidder - BS075

Building Physicist and certified PassivHaus designer Es Tresidder is back to discuss his  EnerPHit retrofit project on his family home. We discuss what he's doing and what he has learned from pulling apart his home to do the work.

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Jeffrey Hart  0:00  
Welcome to building sustainability podcast with me your host Jeffrey Hart, aka Jeffrey, the natural builder every fortnight. Join me as I talk to designers, builders, makers, dreamers and doers. Exploring the wide world of sustainability in the built environment by talking to wonderful people who are doing excellent things. Hello, and welcome to episode 75. As is back to talk more building science. This episode, we're mostly focused on his deep retrofit project, which is his own home. His house is being retrofit to the Passive House retrofit standard, which is called inner fit. But within this talk, we also talk about ventilation and air tightness with airs giving real world examples of what naturally ventilated homes actually look like. And we end up by talking about Passivhaus swimming pools, so it's a little bit of a mixed bag. Before we get into the episode. There's just time to say thank you to our new building sustainability heroes, the new patrons supporting the podcast our Jacob Felton, Dave, no surname, just Dave. Alex Carroll who I will be carving a spoon for Alex because they have gone for the five pound tear. Thank you, Alex. And a big shout out to Ross Langley, who has just upped his monthly support. Thanks to all the new heroes, the upgraded heroes and to the existing heroes it really does make a huge huge difference for your support. Okay, on with the episode

Es Tresidder  1:51  
my house I mean, it's like my house with Well, yeah, I'm using wood fibre board for example.

Jeffrey Hart  1:57  
Why did you choose wood fibre?

Es Tresidder  1:59  
Because what I'm doing so I'm so it's a it's a it's 100 mil deep timber stud framing. And when I stripped the plaster board off, there was like 10 mil of glass fibre, right insulation, glass wall insulation, glass wall or mineral we'll never sure about which is which, but there's the pink stuff. I think it's glass. Well, I think that's glass. Yeah, yeah. So it's like 10 mil of it. And well, it's supposed to be pink quite often it was black in my case, because it was mouldy. So and remarkably like that, you know, they, the people who put it in had done a really good job. It was installed really well. It was just only 10 mil of it. Like

Jeffrey Hart  2:45  
I don't really understand, can you even get 10 mil of insulation,

Es Tresidder  2:49  
it might have been 15 mil, I'm not sure, but it wasn't very thick. It's hard to measure how thick you know that that little mineral is. Anyway, so So what I'm doing is I'm replacing the mineral wool, I've taken the mineral wool out. I'm replacing it with 100 mil bats of hemp and jute insulation, and then I am putting an N There's a racking board on the outside that you can see. Yep, that's already there, adding another racking board on the inside because I'm adding studs to the Windows because there are the structural engineer was not happy about the windows, right, you can see that there's a historic window opening there that you can see and we're going to reinstate a window there. And there's no lentil, which is apparently a bad thing. The structural engineer got very, very excited about that. No lentil and there's only one stood to each side of the window. Yeah, and there should be you know two or three there and then also above that chair that you can see can you see this two full height studs and then two half height studs. And so that was where there was a woodstove flue had been added to the house and they just chuck the studs stuck and flew through the wall. Great. So I've I've added two full sack full height studs there. So yeah, so the the I'm adding an extra sheathing board an extra racking board because those new studs that I'm adding have to be tied together. Yeah, have to be given lateral spot. So I'm adding a vapour open racking board there. And then I'm adding 40 mil of wood fibre board the rigid stuff rigid wood fibre board, type, tongue and groove Yeah, I think it's multiforme or ultra firm I can never remember which stuff the new tech stuff One of them's got tongues and grooves and one of them doesn't. I'm using the one with tongues and grooves. And principally the reason I'm using that there is because that's the easiest thing to fit onto. What I'm doing Yeah, and the tongues and grooves is good because it's easy to get gap preinstallation And, and then and then I'm putting a vapour barrier in. And then I'm having a service cavity. Yep, that will have a bit more insulation in it, and the vapour barrier is going to be intello. So that's able to that, you know, principally most of the time, the vapour pressure is from the inside to the outside. So it's stopping vapour getting in from the warm humid room into the wall. But in some summer conditions, the vapour pressure can be reversed. And in those conditions, the the intello can open up and let moisture back into the room. So it can dry in both directions basically. And the reason I wouldn't necessarily have used that on a new build wall, because I would have been more in control about what the vapour permeability of the outside surface was. Right here. I've got ply, and I didn't put it there. And I can't do anything about it. And I'm not sure how vapour permeable it is. I want the wall to be able to dry out in both directions. Yeah, exactly. So why am I using woodfired board there? Like the fact that it's thermally? Massive and will help with overheating is nice. But that wasn't part of the consideration, really. Although well, I'll probably be using it on the roof. And it will be the part of the consideration there. Because that we get much more direct sun on the roof. And it's black. Basically, yeah, you can you can fix it to the studs. And it's, it's it's it works. From that point of view.

Jeffrey Hart  6:32  
Yes. So you're covering covering all your, your thermal bridges with with the board. Yeah.

Es Tresidder  6:37  
And it's really interesting doing this benefit project? You know, this is such a huge question like how deep should you go on retrofits. And going back to what I was saying before about how one of the things I learned at the airstrip was that people who've invested lots of time can't be trusted to be unbiased. So I'm in that situation now. Yeah, I'm investing like, absolutely enormous amounts of my time into doing this benefit, and trying to remain objective and what I think of it, and it could go either way, you know, I could flip to saying, geez, I've spent so much time on this deep retrofit is definitely not the way forward, it's just way too hard. You I could easily see how someone could get to that point from what I've done so far. Or I could be like, really defensive, because I've put so much emotional, you know, worth into it. But it's really interesting in my house, because so on the on the walls there, where the studs meet at the corners, I think they're just meeting like there's there's one stone in one wall and one stood in the other wall. And there's a gap behind it. And it might have 15 mil of insulation in it. Right, but it might not have anything at all. And even if it has 15 mil insulation, it's basically nothing. So if I wasn't adding the 14 mil of wood fiberboard, inside of that, at each corner, I'd have a bit where there was no insulation at all, essentially. So to not do that, to not add that insulation, it would you probably end up with mould in that corner.  

Jeffrey Hart  8:14  
maybe a weak spot.

Es Tresidder  8:15  
Yeah, maybe you could get away with it. If you're insulating the service cavity. Maybe that'd be okay. But, but I keep coming back to this idea of like, okay, well, what I'm doing is really radical. And part of the reason I'm doing it is because I'm interested in these things. I'm interested in like, How good can you make a crap building and, and also because I like a challenge, like biting off more than I can chew.

Jeffrey Hart  8:43  
And you like living in a little a little shed in your garden

Es Tresidder  8:49  
with a family of five. So, so, but I keep coming back to this idea of like, okay, well if if, if we if we instead we did a shallow retrofit on this house, what would that look like? And I can't see how it would be very much less work like the floor for example the floor, so the floor was suspended floor, no insulation at all. So just carpets on floorboards and then a ventilated space underneath it. No insulation, no draught proofing at all. When we when we pressure tested the house, we depressurized it and the carpets are lifted. Because you know air is seeping through each crack in the floor. And you know, you always had cold feet because the floor was always cold. Yeah. And what I did was I lifted all floorboards up and then the joists are 180 mil and I extended them with plywood by another 100 mil. And then I suspended a vapour permeable membrane underneath like between the joist extensions that had made and filled that with loose fill wood fibre insulation and then put an air tightness vapour barrier member And on top of that, so I had turned on 80 mil of insulation, and that gives you like a U value of point one, five, which is what you need to get to NFA. If you're doing so there's two ways of getting to NFA, you can either hit the model heat demand of 25 kilowatt hours per year per metre squared. Or if that's too difficult, well, oh, you can hit the required performance for each of the things that you do. So the required you values for your floor and wall roof, the required performance, the windows the required performance for mvhr. And because my because I'm adding installation internally, I can't get to 25 kilowatt hours per metre squared, because I can't add very much insulation, I can't get to super low values, my walls, yeah. But for my floor, I need to get to point one five to meet this component method. And so that's really obvious point. Like, if I was if I was gonna go for a less, if I was gonna go for less than no fit. The obvious thing to do on the floor would be not to extend the joists and just to insulate 280 mil, and that would, it would be quite a bit easier. I think. I mean, it's hard to tell cuz I haven't done it. All I've done is the more difficult version. But it'd be a bit easier. But you're still lifting all your floorboards and moving all your kitchen, you've gone to all that trouble. And as well, yeah, it's not like, Oh, that would be really easy. It's still like a massive job. And like, you know, the kind of like, well, you could stick a little robot in underneath that would spray foam and the floorboards like my floor. Void was just full of so much crap, that wouldn't have worked. It was like, massive kind of 200 mil warm air heating ducts from the 1970s. Okay, there were there were, you know, blocking that we're not used anymore. I didn't know they were there until I took the floorboards up. Yeah. But you couldn't have insulated it with a robot spraying foam or you couldn't have insulate it well with the robot spraying foam.

Jeffrey Hart  11:58  
Yeah. Would you have wanted to do that? 

Es Tresidder  12:01  
No. But I'm interested in in in the sense of, I'm interested in it, because I'm interested in how you can drive retrofit at a mass scale, because that's what we need to do. Yeah, sure. I haven't looked into it in detail about the either the performance or the health impacts, because I knew I didn't want to do it here. I wanted to do it myself. Yeah, yeah. Yeah, I'm not sure on what I'm not sure what the deal is, with the health impacts of that stuff. I'm not sure what the deal is, in terms of the breathability. Like, it's quite where the floor is quite a lot riskier than, than the walls because because in a wall, you've got ventilated cavity that's vertical. So the air can set up a convection current, and that can drive quite a high air change rate. Yeah. And in a floor, you don't have that because it's horizontal. But you've got these timbers and your floor that are structural, and you don't want them to get damp. And I don't know how well that kind of stuff does with that. But maybe it's okay. I haven't I haven't looked into it in detail. And I don't know, you know, in terms of air tightness and stuff like that. It's, it's, yeah, so so it's really interesting, but certainly for this type of house. Like on the walls, for example, I remember when I was speaking to a builder friend about what I was going to do to the walls, he was like, why don't you just put foam back plaster board on with I guess without taking off the existing plaster board, just, you know, just put foam back plasterboard on. And the, you know, this, the stuff that's in my walls is disgusting. And it would get worse with foam at plaster board. Because you make everything colder, you haven't necessarily improved the air tightness very much. So you've still got warm, moist air leaking into your structure. And back again, you know, like, I think there's a you were talking about this with John about, like, natural, that kind of appeal to nature logical fallacy. And I'm definitely susceptible to it. Like I like natural insulation, because it's nice. Yeah. And because I like the idea that we can grow stuff rather than having to dig it up. But I think that one of the biggest coos for the crap building industry was calling crap ventilation, natural ventilation. Because it's because people think, oh, natural ventilation That sounds nice. Yeah, I'm compiling a series of photos from my retrofit of like, if you think like leaky buildings is the appropriate way to ventilate your building. Have a look at these. It's just this like where it was most leaky. That was also where it was most mouldy because, you know, air leakage brings moisture in where it was most leaky was also where it was most full of rodent faeces and rodent skeletons because they also can get enough air can get in or you know, if a rodent can get in then loads of air can get in. And yeah, we know that air was leaking in and out of those and that's where the air for the house was coming from, you know, doesn't really matter. Really?

Jeffrey Hart  15:03  
When was your house built?

Es Tresidder  15:04  
1975. Okay, so it's quite early for, like most houses now built in Scotland, our timber frame. That kind of timber frame was rendered bloodwork, like white rendered black work outside. Yeah. But then that it was quite new for them. I think this this style of house. So it's really interesting. Like, it's so mouldy. Well, it's not, it could be worse. It's not having had any timber that's so damp. It's structurally a problem. Yeah. Okay. I haven't got to any timber where I've been like, Oh, I've got to replace that. I've got to timber that's wet to touch, but it hasn't rotted yet. Okay. And I'm pretty confident I can fix that. But there's just a lot of black mould and white mould on that sheathing board. It's quite often white mould. And on the insulation, it's quite often black. And that stuff's not good for you. It would be it would be very interesting, I think to take apart a house that was built more recently than, than this one. Because we're still very bad at doing air tightness, generally, as an industry,

Jeffrey Hart  16:18  
unless, unless you're really into air tightness. Exactly.

Es Tresidder  16:23  
Yeah, yeah. And, and yet, we're putting in much more insulation. And that combination is more risky. Like the more insulation you add, the colder your sheathing board gets. And so the more risk of high humidity and condensation or is there. So it'd be really interesting to pull apart a house that was built in like 2005 and see how old it was. But I suspect it'd be pretty mild. Especially as like, you know, in this part of the world, it's it's often raining when they're building the houses. And they'll just like, spray the sheathing board with bleach and then stick the insulation in. So there's a load of built in moisture from the start. Right. And, yeah, it's just really shoddy. Yeah, I was reflecting about my house. Like someone someone said, Are you do you wish you'd never started? Because it's so much work. And they just think Well, no, like, everything that I've done. Everything. Every time I've taken something apart. I've been like, wow, I'm glad I'm sorting this out.

Jeffrey Hart  17:30  
Yes. You know, you know what you're dealing with? And yeah, yeah, that you want rid of it.

Es Tresidder  17:36  
Yeah. And you know, I kind of know as a Passivhaus designer that building building projects are often a bit shoddy but haven't once opened something up and thought, oh, they did a good job here. That hasn't happened ever. Everything that you open up, you're like, wow, they did this really. A couple of days ago I opened up the windows one of the windows around because I wanted to get i i set about ordering Windows ages ago and I've done it estimating the sizes of the openings. And then that ordering Windows is complicated more complicated than I anticipated, I can see that you've had this like, you know, the the list of questions are so long that by the time I'd answered them all I completely stripped nearly all the wit all the timber frame or all the surrounds so I could actually measure between the stones and give the exact structural lengthening. So I had one window left to do and I stripped that off. And quite often in a timber frame house they'll they'll instal the window frame in the ventilated cavity. Okay, so like in thermal performance terms, you should instal it in line with insulation because you don't want to sell a bridge there. And but quite often, I guess for weather really is that they'll the outside of the the outside of the window frame will be sitting flush with the rendered block work and the inside of the timber the window frame might reach the timber frame or it might not know there'll be a cavity closer in there and there should be a cavity closer in there for fire safety. So one of them I opened up the cabinet there was a cavity closer, but there were like gaps in it that were big enough I could put my finger in a bit shoddy in terms of fire performance. But the one I have been told the other day that they installed the window frame the rear of the window frame was in line with the back of the bloodwork Okay, so it was completely It was outside the ventilator cavity. So your your the window is essentially outside the house all the time. And there was no fireproofing of the ventilator cavity. So like, even if you don't care about thermal performance, it's like totally illegal in terms of Fire performance. And yeah, and it you know, the windows are up vs. Up UPVC, double glazing that don't look that old, I would be surprised if they're more than 10 years old. So it's not like something someone did 20 or 30 years ago when they didn't understand these things. So, yeah, it's quite, it's quite an eye opener. Yeah.

Jeffrey Hart  20:23  
What have you gone for, for Windows by the way,

Es Tresidder  20:26  
I've gone for green building stock Ultra on the ground floor. Nice. So we've got a funny situation where, like the what I've done so far, it's all been me doing it myself. And I can do as as someone who's keen to learn, and watch lots of YouTube about how to do stuff, I can do all of the ground floor insulation, I can do the wall insulation. But what we're doing upstairs is really radical and not really related to thermal performance. Okay, so it's one of these houses where it's one and a half stories, which means that the, the eaves at the front and the back of the house is at first floor level. So internally, you lose loads of space on the first floor. Compared to the size of the footprint of the house, there's like a big section of the room at the front and a big section of the room at the back that you can't use because the ceiling level is too low. So we're actually taking the roof off and rebuilding the first floor walls to be to be one in three quarter stories, which means that the, the eaves, the room height will be two metres internally. And that gives us enough room to mine and my wife's bedroom will get bigger, and it will get an ensuite shower, and a little corner office. So the room itself will be bigger and there'll be two other little rooms. The the main bathroom will get bigger, my daughter's room will get bigger. And my sons who currently share a room, their room will get big enough that it can be split into two bright spots substantial then, yeah, quite a lot of extra room. And then the other thing is that we've got this amazing view to the south, which you saw earlier. It's like South East, and we have almost no view like directly to the west or the east. Like from the gable of gables of the house. And the bedrooms at the moment. Two bedrooms either side of the house they have they only have windows and the gables. Okay, so like our bedroom window. Looks at a tree that's three metres. That's like four metres away. It's not particularly nice tree. And my boys room looks directly at the neighbor's wall. Right? And you know, when there's this like world class view, correct. Look at the cat. See that? She's gone exploring. I don't think she has been up there before. She can obviously smell Rodin. Yeah. Yeah. So for listeners, the cat just climbed up the timber frame wall and into kind of a little void above a bay window. So what was I saying?

Jeffrey Hart  23:21  
View view from your boys room...? 

Es Tresidder  23:22  
Yeah, so we've got this amazing view to the south, and two of the two of the three bedrooms have no view at all. So there are rooms that you kind of tolerate for eight hours a day when you're asleep. But they're not nice rooms to be in. Yeah, at all. And then we'll get a view of Ben Nevis, basically. So we'll get more space, and those rooms will become nice to be in. That's a good thing. But yeah, it's gonna it's going to that's going to be the thing that's really, really expensive. And so when we look at it at the end, we're like, how much was your NFL? Well, actually, it was astronomically expensive. But the kind of actual NFL a bit of it is not the expensive thing. In this case. It's the fact that we're doing something absolutely crazy to go upstairs. And I still can't decide whether it's the right thing to do. We're committed now. 

Jeffrey Hart  24:08  
So I mean, really? It's a complete reroof Is it

Es Tresidder  24:11  
complete? reroof and rebuild of the first floor? Yeah, yeah. And because of the vagaries of the site, it was difficult. We thought about extending instead, because we needed more room. And it didn't really work like this, we'll end up with a much better building at the end of it. Yeah, it's that kind of situation where you're like, Well, you could sell the house and build somewhere else. But we really like exactly where it is, is an amazing place to live. It's, it's, you know, it's got this fantastic view of the mountains and it's walking distance to primary school walking distance to high school cycling distance to Fort William. Yeah. Next to a train station. You know, it's it's really, really good and most of the places that you can buy to build here, you will end up for carrying children in a car most of the day, all the time. I'm quite keen to not spend the next 10 years driving kids back and forth.

Jeffrey Hart  25:11  
Understandable. Yeah, that's gonna be really interesting. You're gonna get the best of both worlds or experience of both worlds, aren't you? Because you essentially have a ne w build? First floor? Yeah, yeah, can control all of the things and yeah,

Es Tresidder  25:27  
and the construction there is going to be very different. We're gonna have a joist walls 300 mil of insulation. And, you know, it's essentially going to be a new build passive house from first floor up. Yeah, it's interesting. Like, I kind of look at what I'm doing on the ground floor as, as a kind of testbed for being able to say to people, this is what you could do to your house. And I think that's reasonably feasible. Like, if they're willing to pay people to come in and do it, it could be quite quick, like, it's taken me ages, but I'm one person on my own. And I'm having to learn how to do it. Because all my all my knowledge is like, computer based, I don't have I don't have any experience of building stuff. So I've been really slow at it. But I would be quicker second time around. And. And yeah, I could certainly help a build team be quite quick. It's quite a quite a lot of things where you kind of come across it, you're like, oh, crikey, that's, that's tricky. How do you do that and thinking about like, the level of knowledge you want your retrofits to have, it's quite eye opening, like just simple things like because I was adding 14 mil of insulation, and then an insulated service cavity. It meant that I couldn't just put my floorboards back to fix the wall where they were, they're going to be before, because then they would have been in a zone that was very cold. But they would be inside the vapour barrier, and they would get damp and rot. Yeah. And that's what would normally be done. I think there's a lot of pitfalls that you need someone who understands those things, I think looking at your project and thinking hard about it,

Jeffrey Hart  27:07  
there was there was the retrofit push a few years ago in think it was probably just in England, but there are a lot of houses got insulation slapped on the outside. Yeah. Done by largely people that didn't have a really good eye for for these details on kind of what could go wrong. And yeah, they've kind of ruined quite a few houses by creating more problems. And they, they sold

Es Tresidder  27:36  
Yeah, yeah, it. And it's the sort of thing like, I discuss it a lot with people, you know, just parents, watching the kids do sport or whatever, talking to parents, they're like, Oh, I'm insulating this, this and this. And it's, it's a funny industry in that it can't really imagine, you know, as a surgeon, if you're like a heart surgeon or something, you wouldn't, you wouldn't have a conversation about oh, I'm thinking about doing a bit of heart surgery. I might might do some heart surgery tomorrow, my wife. Like, but it's a similar, like, obviously is less serious. But it's similarly complicated, you know, and there's this, there's this feeling that there's this idea that you can that anyone can do it, you just slap some insulation on. Yeah. And it's quite hard to get to get across to people that it's not actually that simple. And that they need to think really carefully about whether they need to either, like, learn a lot about it themselves, or get someone who knows about it already. Yeah. Yeah, I think it's it's difficult to know how, how to address how to how to approach that when you're talking to people who are doing it themselves, and you suspect they're doing it, not very well. Because it'd be it would be very easy to come across as a bit of a prep. Yes, yeah. If you're doing it wrong. Well, I

Jeffrey Hart  29:01  
mean, as someone that's been told that I was telling people the wrong things by you.

Es Tresidder  29:08  
did that come across, okay? 

Jeffrey Hart  29:10  
Oh, yeah, It was. I have never felt so so pleased to be corrected. 

Es Tresidder  29:14  
Oh, good. Okay, 

Jeffrey Hart  29:17  
So you've obviously got a nice manner to

Es Tresidder  29:19  
Yeah, I think you have have to do it in a way that doesn't. I mean, essentially, like I came from exactly the position you were at, you're in terms of all the things that you said. I had, I could remember saying to other people. And so yeah, that's that's good. Like the fridge thing. Well, let's talk about the fridge. Oh, yes. Yes. remembered about the fridge thing. So like I remember to I remember when I was working at the Earthship using the fridge thing as an example. And I think it's completely wrong. Like, I think so. The full fridge thing. I think it's because if you open the fridge door, and your fridge is full of stuff, there isn't as much air to the left and be replaced by warm air. I don't think it's to do with the, I don't think it's to do so well, maths. And you can imagine that, like a fridge full of let's say you had a fridge stack full of milk. And it might be out milk, if we're eco enough about it. So let's say it's a fridge stack full of oat milk, compared to an empty fridge, you open the door, the empty fridge has loads more change. So it needs to say it's lost, it has lost more heat, because more and more more air has changed. But if you left them both open for for the day, then all of the oat milk would call too warm to room temperature. And it would have gained a lot more heat. Because there's because of the thermal mass. And then you close it and it would have to work harder to cool down again. But it's it's yeah, it's right there full fridge is better, as long as you don't leave it open all day. Yeah. But you know that you can't really apply the same to your house. Because if you fill your house with stuff so that when you open the doors, there wasn't a high air change, a lot of air change rate, a lot of air to change, because it's full of stuff, you'd end up living like one of those people who's got a chronic hoarding problem and has to be, has to like tunnel out of their house because they've stored every newspaper for the last six years.

Jeffrey Hart  31:16  
Yeah, it's not to say that people don't do it, but it's very practical. Exactly, certainly changes your way of life.

Es Tresidder  31:23  
There's actually there was there was a case wasn't there where a guy like a guy died. And he had to be his house was he'd collected newspapers for like, decades. Yes. And kept every single one and had like this series of very, very ropey tunnels amongst his newspapers. And yeah.

Jeffrey Hart  31:45  
And no one talks about the energy efficiency of that.

Es Tresidder  31:50  
I suspected didn't need much heating because they just had these tiny tunnels and apparently quite a metres and metres. metre you have lots of rats and metres and metres of cellulose insulation. Yeah. I'm curious. I'm curious about your tiny house. I had a look on your blog. I couldn't find stuff about your tiny house. Am I looking in the wrong place? No, I have you written stuff about it?

Jeffrey Hart  32:14  
I haven't yet. That's why my blog is is years out of date, I think.

Es Tresidder  32:20  
Yeah. So it's mine. As I think, I think what happens is, is you kind of have this thing where, or I had this thing where I was newly qualified as a pacifist designer, I just finished my PhD. But I didn't really have any work. And so I did loads of reading loads of courses, and loads of writing on my blog. And then I got loads of work. And I stopped doing any of those doing those things as much. Yeah. And I think there's a I think I remember Nick grant saying something about how being underemployed was actually very valuable because it allowed you to spend time learning stuff.

Jeffrey Hart  32:58  
And it's true, like learning and broadcasting. Yeah.

Es Tresidder  33:01  
Like now I'm, I'm too busy. And I've started my house retrofit. And I'm doing a Twitter thread on it. But I haven't got any time to do a proper blog about what I'm doing. Because I feel like well, an hour or two spending that is an hour or two not doing my house.

Jeffrey Hart  33:18  
Yeah, absolutely. I feel totally the same. I've got plans to kind of write everything up. At the end. Yeah, not Yeah, I will obviously move on to the next project and be Yeah,

Es Tresidder  33:30  
but yeah, that would be how close to finishing a

Jeffrey Hart  33:33  
I'm pretty close. I have got well, here's my to do list. And half of those gas and waters already. Mostly there. The kitchens mostly there. The electrics are mostly there. Right. So

Es Tresidder  33:48  
what what gas out? Are you have you got bottled gas,

Jeffrey Hart  33:52  
bottled gas. Yeah. So for cooking, and for hot water at the moment. Again, you know, the dream is to go to electric. But I am faced with the reality that I can't afford the solar system to.

Es Tresidder  34:10  
Yeah, I mean, you're you're you're off grid, so you'd have to have a big battery and a big solar system. And you're in some woods, so presumably the solar resources aren't that great. Or if

Jeffrey Hart  34:21  
it's not, I mean, I've got I've got free rein to cut a clearing. So it's, it's alright. And it is yours relatively self facing on a slope. So yeah, it's not the worst it could be.

Es Tresidder  34:35  
And what have you done in terms of ventilation?

Jeffrey Hart  34:37  
I have gone for two Blouberg decentralised units. Okay.

Es Tresidder  34:43  
Is that a decentralised? mvhr? Yes. And are they working? Are they installed?

Jeffrey Hart  34:48  
They are not they? I've actually all I've got to do is put the wire in that one and then working and I will do that first thing tomorrow. Okay, quite exciting.

Es Tresidder  35:00  
And the the mvhr units that you've gone for. I've not heard of them. And they were they good? Do you think like, they're gonna be good?

Jeffrey Hart  35:08  
I really don't know. I spent so long fretting about their ventilation. Yeah. And I spoke to ventilation consultants and they tried to push me into getting a ducted system, which would be ridiculous in this. How big? How big is the house? Two and a half metres by six and a half feet.

Es Tresidder  35:31  
So what why do you need two of them?

Jeffrey Hart  35:33  
Well, that was the one thing that my my consultants said was that they wanted that too for airflow. I mean, I'd have I'd happily see one of those holes up.

Es Tresidder  35:45  
Yeah, I mean, I haven't looked at the numbers, but I would have. I would have thought you could do it with a, like a single. There's a blue Martin, I guess Blue Mountain free air soon? Oh, yes. That one pacifier certified one that I think goes up to like 70 cubic metres per hour. per hour. And usually for one person you'd want, like 30 cubic metres per hour.

Jeffrey Hart  36:12  
I think the concern was that it is one person but it's also a kitchen and a bathroom.

Es Tresidder  36:18  
Yeah. Yeah, that's yeah. So on something very small like that. You end up sizing it on the number of wet rooms rather than the number of people? Yes. So yeah, yeah, that might that might stack up. So you've got a kitchen and a bathroom?

Jeffrey Hart  36:32  
Yeah, pretty much half of my floor spaces, kitchen and bathroom, and half living space with a little mezzanine. sleeping loft

Es Tresidder  36:42  
with good fairy lights on it.

Jeffrey Hart  36:44  
Fairy lights and around with timber frame. Yeah. So yes, I mean, I'm intrigued about the whole mvhr thing, because just I've I was for a long time, I was in the viewpoint that we should just make houses just a little bit leaky. You know, and for sort of part of that kind of hippie building, you know, trained in on the west coast of Oregon, you know, I'm fully in that mindset of Yeah. And it's taken me a little while to, to listen to people and understand and

Es Tresidder  37:25  
yeah, yeah. Did you speak to Judith Thornton about that? When She?

Jeffrey Hart  37:29  
She? Yeah, well, she gave me a schooling on tape.

Es Tresidder  37:33  
Right on airtightness. Yeah, yeah. And that I that changed, changed. Yeah.

She's brilliant. She was she was my kind of one of my favourite lectures, when I did the MSC at cat, Oh, great. But she was very good. I kind of arrived, I kind of arrived is like, some of the thinking chips are great. And that recycling rainwater was a good idea. And like harvesting rainwater was a good idea. And I remember after the first week being like, okay, maybe she was quite convincing.

Jeffrey Hart  38:11  
Yes. She's very convincing. And she's also just very direct.

Es Tresidder  38:15  
Yeah, yeah. Yeah. Yeah. Yeah, she's good. And I, we I did, I did some I helped her with a blog post about air tightness and natural building materials. Okay. That was, I don't know if it was before or after you did that interview with her. But a similar thing, like, the fact that there is this. People who like to build with natural materials tend often tend to have that prejudice that natural, natural ventilation is also better. Yes. And but because they're building with natural materials. They're building with biodegradable materials. And so actually, they should be even more careful about, about moisture risk than an air tightness than than in an old building. And I think it's really I've had this conversation lots with people recently. I've got a friend, I can't persuade him that I'm right about air tightness. And he's like an experienced builder. And it's, I kind of run up against this in my professional life, all the time that that people are like, Well, what do you know, you're not a builder? Or what do you know you're not an architect? Or what do you know you're not an engineer? And that that's a reasonable starting point. But like, I think that the confusion is that people confuse breathability and air tightness. And they think that a building, they think a building must be breathable, which isn't true. And we can talk about that as well. But, but they think breathability is good. And in some instances, it definitely is. And they think therefore air tightness is bad. Yes, and The two things that are different you can have a very airtight building that is also that that is also breathable, because it's vapour permeable. And it's a similar thing to the mass thing, the confusion about temperature and heat. Like that they're related, but they're not the same thing. Yeah, and breathability and air tightness people conflate them they think it breathability is like how easily can water vapour move through a structure? And air tightness is how easy can air move through a structure? Yeah. And in a timber frame, for example, you want you want breathability from the vapour barrier outwards. You want the vapour barrier has been not breathable at all. So that moisture doesn't get into the frame. And then from then on, you wanted to get out as easily as possible. Because you want to stop moisture getting in at any moisture that does get anyone to get out. But you can dump orders of magnitude more moisture into your, into your buildup by air leaking through it, then you can buy vapour moving through it through fusion. And it's really I find that really interesting. Like how do you communicate? Something that is so ingrained? That is basically a misunderstanding of language? I don't know. I don't know what the answer is. Maybe you just need Judith like standing up saying no. You're wrong. Yeah,

Jeffrey Hart  41:20  
I mean, I think the Yeah, I mean, the term breathability is is just confusing, isn't it? Yes.

We think of breathing as breathing air. No moisture. Yes. So

that that's a bad term. And I also think air tightness is it doesn't sound like a good thing.

Es Tresidder  41:38  
Yeah, yeah. It immediately makes you think I'm gonna suffocate. Exactly if we get lots of that. Yeah, I think that I've not thought of that before. But that's a good point. That

Jeffrey Hart  41:47  
so they're too Too bad words for for Yeah.

Es Tresidder  41:52  
For air tightness that makes it sound better. Yeah, we need a new word for natural ventilation that makes it sound worse that I think was it was it was it Kate the selling Court I think called it uncontrolled leaky ventilation or something that wasn't it wasn't catchy, but kind of summed up what it was

Jeffrey Hart  42:14  
intello the intello membrane? Are you saying that doesn't let vapour through? Yes.

Es Tresidder  42:19  
So anything like so vapour permeability is something like a membrane is always got some degree of vapour permeability, it's, it's very hard to have something that's completely vapour impermeable, and the things that are completely vapour impermeable are things like aluminium, okay, which is why they make crisp packets out of, you know, they have an aluminium coating on them. So a standard vapour barrier membrane,

Jeffrey Hart  42:45  
like a sort of plastic sheet type or an into something tougher,

Es Tresidder  42:49  
like I've got pro climer DEA in my floor. Yeah. And that's, that's, it's, it's airtight, and it's a vapour barrier. And it's not variable. So it's always a vapour barrier. So there will still be some vapour diffusion through it, but but very little. And intello is what's called a variable vapour barrier. And so, typical humidities in a room of like 40 to 60%. It's a vapour barrier. And when the humidity goes very high, I can't remember what the threshold is. I mean, it's not a hard threshold, but it's maybe over 70 or 80, or something, when the, when the relative humidity goes high, it becomes vapour open. Right. And so the way it works is that you've got, you've typically got, like your humidity, if you've got good ventilation is, is between 40 and 60, let's say and so it's, it's acting as a vapour barrier in that in that case, and then in the summer, if you've got sun shining on your wall, that can drive a wave of water vapour from the outside to the inside. And, and so you can get very high relative humidities just on the insulation side of the of the vapour barrier, right. And so intello Because it's high humidity there is so it's 80% Intel a will then allow that will become vapour open and allow it will allow it through to dry into the room. So that's, that's that's how that works. And I think it's just a straight material property of the of the type of plastic that you use, and that it becomes the vapour the vapour permeability changes with with the humidity. There's another one that Seger I think do one that's that's directional. So it's a vapour barrier in one direction and it's it's vapour relatively vapour closed in one direction and it's relatively vapour vapour in the other direction. I don't understand how that works, but you You can see why why they do. Yeah, the place that that becomes really important is kind of flat roofs because it's difficult to do well in terms of having a ventilated space above the insulation. So typically you've got like a vapour impermeable EPDM on top of the insulation. And so normally, you know, like in a wall, your your wall or your roof in a pitched roof, it can dry out to the outside. That can't happen. But because it's a roof, it can get lots of solar energy and that can dry it out to the inside.

Jeffrey Hart  45:37  
Blimey, it's far more clever than I thought. I mean, I've just come from a world of I want to clay plaster the inside and I want to live render the outside. And goodness, yeah, that's a simple thing. Although, you know, there's there's all complexities in there as well. So

Es Tresidder  45:58  
yeah, yeah, it's there's a lot, there's a lot to learn. And there's, you know, there's stuff to learn all the time. I think I'm learning all the time, which is good. It makes you feel that maybe when when the overlap, when do you ever know enough?

Jeffrey Hart  46:15  
Yes. Yeah, very true.

Es Tresidder  46:18  
I'm actually not working. So I was, I think my Twitter bio hasn't been updated. But I'm not really doing my own consultancy. Now. I'm working for John Gilbert architects in Glasgow. Okay. And, well, I'm not working in Glasgow, but they're in Glasgow, and I'm working from home. And I'm doing quite a lot of really interesting non domestic projects. And those, like, just another level in terms of what you need to know, suddenly, like, I'm doing doing a leisure centre with a swimming pool. Okay, that's to Passivhaus standard,

Jeffrey Hart  46:51  
right? That's a lot of moisture to deal with. Yeah, exactly.

Es Tresidder  46:55  
There's a lot to know here. Suddenly, you have to become like, nearly an expert in pool ventilation and pool water treatment, and, you know, like filtration, of smooth pool water and all that sort of thing. It's fascinating, but it's like, totally had expanding.

Jeffrey Hart  47:16  

Es Tresidder  47:18  
Like, it's really interesting, like how there's a kind of cascading series of, of benefits to doing the Passivhaus thing on a swimming pool, which, which is fascinating. Like, basically, because you have a super insulated external shell, and the windows are triple glazed. And with insulated frames, you don't have cold surfaces for the condensation to happen. And so that means that you can tolerate higher humidity in the pool hall, without structural risk to the building. Okay. And that means that you can, that reduces evaporation from the pool, which means that you have less water to heat, because you're not losing water. Yeah. And it means that you're, the evaporation itself takes heat. So you're, you've got lower heat losses from your pool. And because you don't have to keep your humidity lower, your ventilation rate can drop. So it's like these series of interlinked things that all cascade towards it being a much lower energy solution. Wow. Which is really interesting. But it's also like, like, if you, you get this quite a lot as Passivhaus designer, you're, you're saying right, we're going to design a building that uses 80%, less energy. And so like, the logical conclusion is you're gonna have to do things differently from what you normally do. And that's the same for swimming pool, like this thing is going to use 80 to 90% less heating than a normal swimming pool. So obviously, we're going to do things a little differently for normal. And normally, the ventilation system, often not always, but they blow warm air over the windows to stop condensation. And so we don't do that anymore. And normally, they supply air at pool level, and they extract it from high level. And that works in terms of buoyancy because the warm air rises. So your ventilation system doesn't have to work as hard. But in terms of humidity, it means that you're you're blowing the driest air over the pool, right itself and increasing evaporation from the pool. And then when the water the air is picked up, the moisture is then going over the fabric. So in a Passivhaus pool, you do it the other way you extract a pool at low level and you supply at high level. And that means that the highest humidity is directly above the water which decreases the evaporation and improves comfort in the swimming pool. Because like if you're standing in the swimming pool, playing with your kid, your shoulders are out. Then the humidity that surrounding your shoulders and head impacts how fast you lose heat from evaporation. So if you're in a humid environment there, that's better for your comfort, but the people watching who are in their clothes want to be in a drier environment, they don't want to be in humid environments, they get too hot. And so you want to you want the highest humidity over the pool and you want it lower elsewhere. So it's it's really interesting, but just like, so, so big, like so many things that you have to keep an eye on. And

Jeffrey Hart  50:31  
there are other examples that are you leading the way in this hour in

Es Tresidder  50:36  
terms of swimming pools, huh? Yeah, yeah. So no, there's just about to be one certified in Exeter? Oh, yes, I did. I saw that. Yeah, that I'm not involved in we went down to see it. When it was just they were kind of half out of the ground. And that was really interesting. And I hope will go down and say it again, actually went and have a swim. Yeah. And yeah, and then there's two in Germany. So two Passivhaus certified swimming pools in Germany and one about to be certified, certified here. So I don't know if there are any other projects underway. I think, if I was when I was getting built, I think it will be the second in the UK. I don't think there are any others in the pipeline. But there might be. So yeah, I mean, really interesting. And, you know, you can imagine a swimming pool is like a big user of energy. So the the, the the, the potential gains are really huge.

Jeffrey Hart  51:33  
And yeah. Do you reckon a 90% reduction though?

Es Tresidder  51:36  
Yeah, I'd say 80%, maybe maybe not 90 in heating demand. So other energy might not go down as much as that but the heating demand is the big thing for a swimming pool. Well, no, that's not true heating demand, but also like pumping water around. It's also high energy demand. So I've had to learn a lot about like how you minimise the the energy demand of pumping water around that you don't think about at all in buildings in domestic buildings, because you're already doing it very much. So yeah, really, really interesting. A long way from Earth ships. How far you've come ships swimming pool.

Jeffrey Hart  52:32  
Es! What a splendid chap, and what a splendid chat, I'm wishing him all the best with his build. The progress he posts on Twitter is inspiring and really beautiful to see such a good job being done. There was lots and lots of discussion around as his last episode, both in the building sustainability community, Facebook group, and also on Twitter. There are links to both of those in the show notes. So do get involved and ask questions, as is in the Facebook group, and very active on Twitter. So you'll get an answer to your questions. So if you've enjoyed this episode, please do give it a quick share. It really does wonders for the podcast reach. And I see big jumps in listenership whenever you do so. So it's really appreciated. And you know what, it'd be good to spread a bit of positivity and a bit of forward focus, doing the right things doing them? Well, I feel like at the moment, it's it's hard is hard to stay positive at the moment, the IPCC report, which states very clearly that we need to act now. And we need to act hard to avoid catastrophic consequences, has been totally ignored by those in power, for what I can only see as reasons of greed is utterly crushing to me. It doesn't fill me with any hope. And maybe it's just because I am at the end of a very long and tiring build project. Maybe I haven't got the energy to stay positive at the moment. But I would say that running away and living in the woods and putting my head firmly in the sand has never felt so appealing. So that's a bit of a downer to end on. I hope you're well. And I hope that you're doing loads of really great things and spreading positivity in whatever you're doing. All the best and until next time, bye bye.


Es TresidderProfile Photo

Es Tresidder

Building Physicist & Certified Passivhaus designer

Highland Passive help self-builders, architects and design teams to meet the rigorous international Passivhaus standard on both new-build and retrofit projects, helping you to live in a cosy, healthy, cheap-to-run home.

Highland Passive is run by me, Es Tresidder. I am a certified Passivhaus and AECB Carbonlite Retrofit designer. I have over ten years of experience in low-energy buildings in both consultancy and academic roles. I also teach on two Masters courses (Developing Low Carbon Communities and Sustainable Energy Solutions) for The University of Highlands and Islands.