Aug. 1, 2022

Retrofitting to EnerPHit standard - Gervase Mangwana (1/3) - BS083

Retrofitting to EnerPHit standard - Gervase Mangwana (1/3) - BS083

This is the first of 3 episodes with Gervase Wangwana - a Retrofit specialist,  Airtightness tester and reformed DJ.

Part 2 will look more into ventilation and part 3 is all about air tightness.

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a small squalid or simply constructed dwelling.

"people were living in rat-infested hovels"

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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 the podcast. This is episode 83 With Gervais mangwana This is actually the first of three episodes with Gervais I'm going to trickle these out over the next week or so. This episode is about Gervais his backstory about his own retrofit projects, and particularly about his inner fit that he did a few years ago on a little cottage in Herefordshire. The next episode, Episode 84 will be about ventilation and more of a sort of general retrofit, how deep to retrofit and then part three will be all about air tightness. It was a wonderful three hour conversation that just flew by. Yeah, I'm excited for you to hear it. So I first met Gervais when he was doing his Herefordshire and if it project on his own house, and I was brought in to do an earth floor. And we chat a little bit about this in this episode. It was I think it was the last day when we were sat around at lunchtime, and we were talking about our previous lives. And Gervais told me that he'd probably been a globe trotting DJ superstar and I actually realised that I danced to him DJing in London many years before, and in fact, he was quite heavily involved in the music scene that I was into. So that was a lovely little surprise. Also, we found that we had a mutual connection in meditation. Both of us have done for Pastner sittings that comes up a little bit over the next few episodes. So a little bit of background is it's a 10 day meditation. You can do longer ones, I think Joey's did a 20 day one. And you go and you sit in silence and you meditate. Yeah, I've I've done a couple now. One in Canada and then one in Herefordshire. Just down the road from Jabez. As I mentioned at the end of the last episode, I am going to take a little break and enjoy not building my house for a little while. Hopefully go on a long, long bike ride. So yes, no podcast episodes for a little bit, or what else to say patrons. First of all, welcome you and McCaffrey, thank you so, so much for supporting over forward slash building sustainability. There's a link in the show notes. Everyone who supports is a total hero. And I really struggled to express just how much it means to me. So thank you, everyone, you and all the existing supporters. I've got a competition running throughout August. So if you've been on the fence about supporting, then maybe this can lure you in. And it's a beautiful hand woven pack basket. And that is a woven backpack. It was hand woven by me. And if you want to win it, all you got to do is become a patreon supporter in the month of August 2022. And I'll draw a name from that. And it could be you. Yeah, there'll be pictures on my Instagram on the building sustainability podcast website. And on the Patreon page as well, just in case you don't know what a backpack is. Also, because I always feel bad about all the people that are already supporting. I've got a bowl that I hand turned I think it's my best ever bowl. So I will give that away to one of the existing supporters. Okay, I think that's everything. I should also say up front there are a couple of little squares in this chat there. So do be mindful of sensitivity is enjoy Jabez.

Gervase Mangwana  4:21  
So I'm sure that he's gonna go on. That's the how that's the way I say it most of the time.

Jeffrey Hart  4:27  
Most of the time.

Gervase Mangwana  4:29  
Always asked me, How do you say your name if you don't know. And I say I don't really know. My mom knows. Right.

And I don't think I've ever quite got it right. So I kind of I've given up caring I generally I'm focused on retrofit. That's my that's my big passion really. But I'm also accredited air tightness tester. And I do yeah, so I also look after fairly well, a modest sized district heat network at the meditation centre that we are both familiar with, to biomass district heat networks that they have there. Because I live just up the road from them. And, and because of that I've kind of got much more Genda on building services than I was before. I used to be a DJ and music producer till about 2008. Until, in fact, I start my first meditation course.

Jeffrey Hart  5:32  
Oh, well, that was the turning point, was it?

Gervase Mangwana  5:35  
Oh, yeah, definitely. Wow. And I went to my first course, I was struggling a bit, I'll be honest. And I think my agent of kind of waging was a friend of mine, he was and it's been a promoter in Leeds. And then he sort of started working for an agency that I was with. And he'd kind of basically asked me to write another anthem, so that he could get me gigs. And I was quite cautious about it. And so I wrote him like a uncharacteristically mean and harsh email, like, and then got on the train to my first ever meditation course, and spent the next 10 days feeling very bad about the fact that I've done this to escape, nowhere to escape. But at the same time realising that it was also it was just a product of, you know, knowing that wasn't really what I should be doing anymore. It took a little while after that, to kind of extricate myself from it. And I did that by moving from London out of my studio and moving up to Manchester to help out a friend who was in quite dire need, who's having a bit of a midlife crisis. And in the middle of a flat conversion, so I've been helping them out for for a while when I was just taking some time off every now and again and doing some stuff and you had one to finish off. And then him spent nine months in the cellar, we're doing this, this flat in a very, very environmentally friendly way. So I had only intended to go out there for a short period of time actually. Then met my wife through through the meditation, we were just we just sat together. And I'd always say I did a I did a degree when I was in my 20s on standard time made a complete hash of it. Complete and utter hash of it was very bad time learning how to make music instead. And so I'd always have a degree in mathematical physics. Okay, right. Yeah. And I was way out of a depth and I kind of wish I was just talking about this quite a lot because I had massive mental health problems basically leaving kind of go to university. And I just was completely unprepared and didn't really realise it. I never realised that I was like chronically depressed and didn't have there was no, there was no support. It wasn't a narrative then at all. So I just kind of ploughed through failed every year, they gave me a degree of shame, I think more than I think it was more because they wanted, it was a very new course. And they didn't have enough people on it. And they failed us all. And they wouldn't have any funding for the next time. So somehow, I literally got like 20% in every year's exams, and they gave me a certificate said you've got a degree, it was ridiculous. But I always had this idea that I really would like to study, but I didn't really know what I wanted to do. And then some friends of my parents suggested I go to cat. Alright, so in 2009, I did the Ruby masters at cat part time, living in Manchester, expecting to be going into wind farms and solar and all of that. And having chosen to do the renewable energy rather than the Harry builders course. Instead, and because I sort of identified more with the maths and engineering stuff, but very quickly, the kind of built environment side of it was the thing that kind of tweaked me more. And living in Manchester, this massive solid wall Victorian housing stock I just, every every module, I did somehow seem to focus on retrofit. So yeah, I kind of came out of there just sort of retrofit focused in 2011 wrote a thesis on moisturing walls, did an experiment in a friend, fellow graduate who was did a retrofit in Manchester and I stuck to the monitoring edge wall and did a did a sort of an assessment of that very, very badly. Probably. Looking back on it, you know, it was just a thesis master's thesis or just an exercise in doing the system not, not really that the research itself isn't as important as you think it is at the time. Yeah. And then I got involved with another cat graduate that was kind of locally funded, local energy funding schemes. And we used that I use that to fund purchasing thermal imaging camera and air tightness fan. And we did a whole load of basically sort of sat based assessments. In talking you mentioned where I lived at the time with the idea of kind of mapping the housing stock there so that we did like like 20 or 30 of them. And the idea was we tried to do as many different types. And then people could kind of identify with the house that was like there's the see the report of it, which is an idea that sort of coming back around a lot more now. And then I retrofitted our house in Manchester, quite deeply, but very much on a budget was quite small place. Which you can see online because the carbon carp did a bit of an interview about it.

And then I started working for the carbon carp. You're probably familiar with how Joe knows what they do. Carbon carp is a member of coal up in Manchester, it sort of thing, it started out more as a kind of energy focused thing, but there was a very distinct sort of retrofit aspect to it. And they do an assessment project, they have an assessment process, and a tool, which is it's basically a facsimile of SAP, the standard assessment procedure, but built into a web based piece of software, so much easier and more user friendly than than sack itself is, and much more. It's not a black box, you can kind of look at all the bits of it and play around with it much more easily. It was developed by Tristan Lee. Okay,

Jeffrey Hart  11:18  
don't interest, you know,

Gervase Mangwana  11:20  
the open energy monitoring.

Jeffrey Hart  11:22  
People know,

Gervase Mangwana  11:24  
opens open source, I don't know about it too much. But they're a bunch of wonderful geeks developed a bunch of monitoring stuff. That's all open source. So there's, there's lots and lots of info, I've got work car charger, but basically, you kind of need to be a bit of a programmer to be able to kind of do it, which is why I've always shied away from getting too much involved in it. But it's it's quite big in the same the, you know, I think it's yeah, it's well liked, but it's, I think it's, it's, it's liked by people who thought it's open source aspect, and it's freely available kind of pneus Yeah, but, but as a kind of robust, kind of very widely applicable, kind of just dumping it on a bunch of ignorant people not going to work so much. That's my understanding of it anyway. Anyway, so I helped them sort of developing the tools so that it was more and more useful and then started doing assessments for them sort of 2015 and that is the carbon carp is now people powered retrofit and lo ha,

Jeffrey Hart  12:28  
yeah, cuz because you're a director or trustee and

Gervase Mangwana  12:33  
the trustee of them now you're a board board member. Yeah, so they launched last year. So they had a couple one of them were one of the base funded pilot schemes there were seven or eight around the country was one in Bristol, Bristol, CSC future proof that lot, so they were one of them. And and they'd be bad retrofit was one of them. So it was a base funded thing for a couple of years that ended last March. And then they decided to sort of go it alone and went out for shares, got a massive load of money together and launched in sort of November. Great. So yeah, it's just so for me it's to sort of carried on from what we were doing and it's just got a lot more serious. They've got a full staff now. We had a staff and board away day in in some otter Seagull houses in a youth hostel in Chester.

Jeffrey Hart  13:26  
Right. I think I think that might have been what I saw a photo. Yeah. So

Gervase Mangwana  13:29  
I was somehow weirdly sort of front and central in that photo. I found myself wearing orange as well. Yeah. So yeah, it's just such a wonderful thing to be involved in. It's so brilliant. And they really kind of so I moved down to Hereford in 2018. A place that I knew because the meditation centre, but we came here so the children could go to the Steiner School here. There's a state funded Steiner School here. And we knew a lot of people who already had kids there from the meditation centre and like in their local community. Plus, it's like it's a real energy hotbed around here. There's Mike work field and diaries, who are both Passivhaus new builders. We've got Nick grant. And Alan Clark. We've got Andy siblings. All gone. George as well. You're just just up the hill.

Jeffrey Hart  14:18  
He popped down when I was working on your floor. Oh, did he? Yeah.

Gervase Mangwana  14:22  
I don't think I knew. And then he

Jeffrey Hart  14:25  
just said, Oh, I heard you're working down here. And I thought I'd come and say hello. And and he said, I just built this little little straw bale house out of panels. Yeah. And I thought oh, that's wonderful. Yeah, really wanted to go and see it. But yeah, it was I think we went a couple of days over on the floor instal so it was did you take over what I what I wanted, maybe but

Gervase Mangwana  14:48  
yeah, sure, I can imagine.

Jeffrey Hart  14:51  
But yes, so it was funny to find out that he's, you know, his strawberry house is is sort of one of the you know, the benchmarks of Africa. You're a passive natural.

Gervase Mangwana  15:01  
Yeah, absolutely. Yeah. clay plaster as well, isn't it? Yeah. Yeah. So he's like, we go riding on Sundays he lives. You know, I can I can walk there. Yeah, he's the nearest. Yeah. Although just Mike's just building another Passive House from the people around the corner from me. So there's, you know, there's a really good I don't know what it is like density wise, but I kind of always was fantasise a little bit that we're kind of got for a rural location. I guess we've got a bit of a passive house and low energy hotspot. Yeah. So yeah, we moved down here. And I initially thought maybe we'd buy somewhere. We had ideas about community getting small, holding a few people together. And so we sort of went somewhere until we saw where the landlord, but I just couldn't quite face living in a non retrofitted house. Right. So we ended up looking for something that was definitely a door upper bound something and initially wasn't going to go for benefit, but I got to Martel who's not that far away, over in Stroud to come over and kind of do a quick PHP period. He said, I don't think you'd be able to get it there. And I said, Well, this is what I'm planning to do. And he went away and came back and said, Actually, it's not that far away. So at that point, we're like, right, well, okay, maybe we will. So we'd say,

Jeffrey Hart  16:18  
can you describe the house? Oh, yeah.

Gervase Mangwana  16:20  
So yeah, it was it was what have I've just recently done assessment for people who said that the original cottage was a hovel, which is obviously it's, there's an actual definition of what a hovel is, which I keep meaning to look up. But I suspect this is what it was here. And I think it was probably one room with a fireplace and possibly a bit of a loft upstairs that maybe you could sleep in when it was originally built. 1838 Yeah, it's called reformed cottage. So it was it was built around one of the reform acts at that time, and I do actually have a lot more information about it, but I haven't yet had the time to I've got the deeds from pretty much every sale since the one after that excluding the one people that I bought it off. I've got everything else. Just stuffed at one time and retired. I'll look through but yeah, so it's, that's the original cottage is tiny. It's sort of like, I don't know six metres by three metres or something. Solid sandstone, and it literally just sits on mud. It's that was one of the things of Andy and I first found out I got Andy Timmons to come out here especially when I first met him properly because he lives in Hereford needed his he did have one of the first retrofits Passive House retrofits in the country, if not the first lady's house in Hereford. So I paid him for some time to come out and we better poke around, see if it was a goer. Basically, I'd done the CLR course, which he was feeling carbon light retrofit the ACBS retrofit course excellent, you know, really good level of information, a lot of levels about retrofit that the ACB runs. And I've done that just after doing my house administration. So I knew him a little bit from that. But yeah, I got him out for like an hour and we kind of poked around the weeds and tried to work out whether it was worth doing. And one of the things we found out was that the stone walls were literally five centimetres, 10 centimetres on clay, no footing. Yeah, just sat there, which was going to make insulating the floors very challenging. And we're muddy, it's Clay, it's very as you know, it's clay. Yeah. So that was the original dwelling. And then in 1900, they extended it doubled the size of it with a solid brick extension. And then it had a double pitched roof. And then sometime in the 70s they lifted that up and put it onto a single roof. So then they got a proper upstairs, left a lot of the original roof inside. We had leaked a lot of the original sort of chestnut beams and stuff were just sort of inside the loft space and kind of very weird and even some of the slates and bits of tar and this is how people building I don't know how people do it elsewhere. But in Herefordshire. As far as I can make out from most assessments I've done there's an old little stone building somewhere in the bottom that people have just slapped stuff on with not much care to kind of tidying up you know, it's just literally it's functional, kind of add it on, add it on, very hard to kind of work out and obviously very little record of them. So that kind of double that and then in 2000 just affordable when I bought it off bought it. Somebody stuck a pretty disgusting brick and concrete block cavity. almost doubling the size of it on the end was and uPVC windows.

Jeffrey Hart  19:47  
Oh, is that the bit sort of far end from the Yeah, from the drive? Exactly. Yeah. With

Gervase Mangwana  19:51  
a weird slanting wall to make the Yeah. So the drive could come down. Yeah. So altogether, quite a mishmash. And I went to the planners with a pre AP to say, look, I want to wrap this totally, I was expecting initially, because PPIs carbon carp are very Woodfibre oriented. And I've done some jobs in Manchester where we used wood fibre, I was quite wedded to wood fibre. But it does particularly then have the disadvantage of cost and poor performance for thickness. But I was expecting to do that. And I was expecting on the sort of front facade of the cottage, which was sort of the nicest off the lot to not really be able to do it on the outside, I was expecting to have to internally insulate that was kind of my initial plan.

Jeffrey Hart  20:36  
Because it because it changed the character of the

Gervase Mangwana  20:39  
Exactly, yeah. But actually, it was a bit of a mess, there was a massive bulge on the front wall. And you could see where they'd lifted it up. So there was this sort of seam across and then the person who have done it in the 70s, it was sort of bits of rough stone in that but it was clearly not the same original wall. Yeah. And the gable end was just a big, which is was the bit that was exposed to anybody you could see the only bit that anybody could actually see was his gable end. And it was just a patchwork of, you know, bricks, bits of concrete, you know, like, you know, not a beautiful old preserve or stone wall. And yeah, the the planning people were great. And they said, Yeah, kind of get it. Now, initially, they said, No, you're gonna have to keep that. And you're gonna have to keep the windows and said, well, which windows, you want to keep the brand new PVC windows or the ones that are in the house that are different from that. She's okay. I said, Well, I want them grey. Because I don't know why. She said, Well, if you can find me, somebody else has got grey windows in her foot and take pictures of them. Turned out Andy had grey windows. So he sent me pictures of his house perfect. Yeah, so. So that kind of gave us the Go ahead. And then we are now moving into my house. So I decided I was going to go for an affair. And Woodfibre was now a wouldn't going to get to with five wasn't going to get to airfield Woodfibre. So I started looking at EPS. And this is one of the things I wanted to talk to you about is actually because obviously we ended up the reason I met you is because you came at dinner floor for me with your team of I don't know, it was like a mix of volunteers. And no, no, they're all They're all paid. They were my they were all paid. But we're on a course or something with a with a learning.

Jeffrey Hart  22:21  
No, no, there was there was a few people that didn't have as much experience that were training up.

Gervase Mangwana  22:28  
And they were Yeah, they were kind of I still use the beam that you can't Hey, and it's because it's got a flap on the top of it. Right? Because you cut the flap out. Yeah. And then put the lid back down again. So I That's great. I just, that's my workshop in schoolwork. Got a freebie now.

Jeffrey Hart  22:48  
I wonder whether

Gervase Mangwana  22:52  
it's just like a thing. You just bought one for every job and left it

Jeffrey Hart  22:54  
Oh, yeah, that's how you just Yeah, single use plastics.

Gervase Mangwana  23:00  
Yes, right. Yeah, of course. So yeah, I, I knew some people who'd had an earth floor. So die diaries is a guy now builds passive houses around here. But he had a renewable energy company called green earth over Galway. And they put their own Earth floors in. I knew they'd done that. The earth floor was a thing. Now we've been aware of it. But because of sequencing, I really need to get the floor in. Something to work off quick. Yeah. And because of the what I've mentioned about the the walls being sat on the ground, I had got a structural engineer who saw who'd I had gone through back to Earth down. Yeah, that's what I used to get my Woodfibre stuff from. So I was talking to him about the potential for doing floors, like glass foam glass floor or something like that. And he'd said that you knew a structural engineer who had had a way that could be possible where you kind of ramped floors where you had you kind of left a kind of 45 degree Hill underneath the wall, inside and outside. Okay. Which obviously, is still going to have bridging issues. Yeah, but but it still means that you can get depth in the middle of the floor, although albeit that's sort of where you need the installation less. Anyway, he was a structural engineer from down in Cornwall somewhere, but somehow I managed to persuade him to come up here. And he came up and said, No, you can't do because of the ground because the ground conditions. So then it was like the only way to insulate the floor was going to be underpin the house, which was a deeply scary or what friend of mine from Sheffield describes those expensive jobs that are very scary and you never get to see.

Jeffrey Hart  24:54  
Yeah, like, you can't really appreciate that everyday

Gervase Mangwana  24:58  
and yet Yeah, so it was, it was a it was a five figure job. Right.

Jeffrey Hart  25:04  
And the job is literally dig a little bit out from beneath

Gervase Mangwana  25:08  
fill sites. 900 mil at a time, I think. Right. Leaving, is it 900 mil segments. I think it's 900 mil segments leaving to 900 mils in between. So you do it in thirds. Yeah. And we went down two feet. I think we went down 600 mil. And I mean, I didn't do this I got somebody yesterday, who was very experienced kind of hands on build retired, you know, like not, you know, not a big firm or anything. Didn't bother him. It didn't appear to bother him that much. And how much he worried about it scared the willies out of me. Yeah, of course. This these still kind of box section Steel's just holding up like 400 500 mil pretty badly built as well. stone walls. Yeah. And and then the brick as well as the solid brick was also just sat. No footing. So like much thinner. Yeah, like, to me it was more like a knife sitting on play rather than, you know, a spoon sitting on clay.

Jeffrey Hart  26:07  
Understand the wide, you know, spread? Yeah, exactly. Yeah,

Gervase Mangwana  26:11  
but the brick, I just couldn't. And yet they've been no problems at all. And there's still there still isn't. So that was pretty much the first job, write the floor out. And then and then get that dug out. But the brilliant thing that it gave us because there was quite a lot of damn problems in the world event that we could put a mechanical, you know, a physical DPC. Okay. Yeah, so damp proof course, an acronym busting. You can buy you can buy like damp proof course that is 600 mil wide, thick stuff. So they, you know, they put this linen laptop for every 900 mil. So where we had walls, like there's a, if you remember, but there's a retaining wall, just on the end of the house and sort of a kind of ditch around the outside of the house. And it's been a lot of moisture, a lot of runoff from the road. And so that corner of the house is sort of the north corner of the house was sopping wet. But because we stripped the plaster on the inside, and because we took the bottom out of it, and it was like that for almost a year before it got rendered. That all dried out. And the new damp proof course means that the big problems that were there would have been with externally insulating with EPS, which was what I decided I was going to do was what is left in the wall, what still can get into the wall, and therefore what will not be able to get out of the wall. And all of that just disappeared without being able to put in a stamp of course. So it was a kind of silver lining in what was otherwise a very expensive, scary job. Because it made a lot of other things possible. But what we wanted to then do was to put the, you know, kind of I now started to use traditional to mean, concrete and and

Jeffrey Hart  27:57  
yes, that's a common thing. You foam. Yeah. Invention is how I would call it conventional. Yeah,

Gervase Mangwana  28:04  
I mean, I use it slightly tongue in cheek. Traditional method is concrete and PU foam. So that's what we did we put PIR in a concrete base. I know maybe, I'm not sure if I'm not sure if I managed to persuade the building neutral, to go for just hardcore, which is what I've done in Manchester, just put hardcore under my PU foam, and then put a screed over the top. Because I didn't want to dig out very much. I think here we were sort of forced into putting a hard concrete base down, huh? Yeah. And then I think we put concrete on top as well. And I was expecting so I would sort of written off that the earth floor. And then a friend of mine who was helping me out another meditator friend of mine is dead is Prof depot cat as well as the architect now. He came down to visit and help out for a bit and he'd been to see John Christopher's house in Birmingham. You know, John Christopher's are no. No, so I don't I don't know him well, but I have actually just coincidentally started working with him on a on a project. But anyway, he apparently had he's got both floors, downstairs and upstairs on suspended timber upstairs floors. And this friend of mine happened to come down and sort of say I've just mentioned it. I mentioned it to the project manager was helping me out. He knew that you just done Ed and marinas place. Yep. So that was that was how you sort of came to all of a sudden it was like, Oh, God, we can have a school. I always feel like we have a bit of a pretender floor because it's a finish.

Jeffrey Hart  29:43  
Yeah. You've got what I would call brown washing.

Gervase Mangwana  29:48  
Yeah. So I'm kind of aware of that. Yeah, so this is one of the things I really wanted to touch on is like my approach. I always think my approach is is it I'm not a purist. I, I am a pragmatist. And so I'm kind of, yeah, I think I try to find a balance between lots of things. It's kind of my nature. I'm a Pisces. I've just yeah, there's otherwise I find it hard to make decisions, I can get quite extreme. And I have found myself getting down quite extreme extreme kind of viewpoints in the past. I try and avoid doing it for my own sanity these days, because I don't think I wear it. Well, yeah. So yeah, I tried to kind of I end up kind of with a sort of mixed and matched approach. So yeah, I Graham washed off laws with with a, and you know, to be fair to me, like, the, I absolutely wasn't going to have it, if the if the clay didn't come out of the garden, which are, which ended up being quite stressful because you needed samples. We were on a schedule. As all these building projects, I mean, it was spring 2018. And we were moving in in July, and we had we had a moving in date. And you needed samples in front to test so that you knew what mix of sand you're going to be putting into it, which you know, with the kind of plays that you'd more traditionally used. So there was a Friday night, we had a digger on site and previously mentioned builder, who'd also done the Wi, Dave, I've been asking them for days can you can you'd like we had a septic tank to put in a treatment plant to put in. And so I knew that down there, there was going to be some clay that we use and been asking them for days, even weeks, like can you just get me a few bits of the clay out of the ground and nobody managed to do it. So it was there on this Friday nights for me as it was getting dark. I mean, Dave had the bigger out. And we kind of scraped off a bit. And then we got to a bit of like, this stuff's a bit, it's not great, but you know, it's gonna have to do kind of thing. And then we went a bit lower. And we got to the kind of, you know, the really good stuff. And then I got that off the year when I knew that down there, there was going to be enough to do the rest of the floor, and I still got bags of it like fine and lying in the garden.

Jeffrey Hart  32:18  
Yeah, because I remember that initial conversation because the difficulty is I mean, as you discovered your your DIG was a really good example. It's like you there are different seams of of Earth, you take, take away the topsoil, and then you go down and you thought like, Oh, this is, this is something, but then you went a bit further and it changed. You went from that grey to brown. And there was

Gervase Mangwana  32:38  
no, it's red, it's all sort of red. It was just, it's a bit mixed. On the top. It had other stuff in it, basically. Yeah, I don't know, if it had been, it wasn't so much that had been turned over, but it just wasn't as pure, you know. And then I think we broke through a tiny kind of bit of, it's hard to call it even rock here, but a little bit of a, there was a little bit of mud stone kind of shelf. And then underneath that was something a bit more. And in fact, going back to the structural engineer, you know, he obviously he had a look at is geology maps for the air. And he said, It is very much there's vehicles themselves themselves have of clay around them. You know, the it's, it's very sort of dispersed. I mean, it's all very red around here. It's very, very red. Well, I was cycling on Sunday and the other side of the river. It's quite, it's quite grey. Actually, there's a bit where they put something on the fields here. It's not red, but then I look to the ground. It's like it's a bit of a different colour. Yeah, it is the other side of the river.

Jeffrey Hart  33:40  
I was Yeah, cuz I was very nervous about using your world leaving you to dig the clay. But then I think you might have sent me a picture or I think I came over maybe, but you were showing me in this hole. And it's like, these guys doing it properly. You know, they're because Yeah, didn't want you to dig a load of one clay and then move to a different thing and dig dig me something else up. Yeah. Could have thrown everything out. So.

Gervase Mangwana  34:06  
So yeah, I mean, my memory of it is that you? You were kind of expecting with your normal staff. You had a mix of like five to once and 20 Something like that. And that's what I sent you this stuff off. And you ended up a 15 to one

Jeffrey Hart  34:23  
yes. Yeah. Well, I it's, it's not a fair comparison, like for like, because I was I was mixing your stuff up to a wet consistency, when we started changes, changes how much clay goes in into one sort of volume? Obviously, but yes, I was very surprised when I didn't expect it to be that strong.

Gervase Mangwana  34:46  
Right. So that's strong, so I've never quite understood that. That's like is the clay was strong. Yeah, yeah. Really strong. So yeah. And then we got we got local sand as well, which is quite a lot of around here. So I was happy you know, so that Is that something that makes me happy makes me fuzzy makes me feel something like that. No, I brown wash my floor but I brown washed it from my garden.

Jeffrey Hart  35:09  
Yeah, I call it brown washes. I mean it's still better than doing a concrete screed or

Gervase Mangwana  35:15  
Yeah, but you know there's a concrete floor underneath it.

Jeffrey Hart  35:18  
I feel I feel bad saying

Gervase Mangwana  35:21  
Don't Don't worry about it. So I it's something that I hold yourself now the the other option was going to be engineered oak because we knew we were having underfloor heating. And I'd had I'd put solid maple down in reclaimed maple down in, in Manchester. Never again reclaimed Yeah, scrape it yourself.

Jeffrey Hart  35:46  
Oh, yeah. Yeah, like a gym floor type.

Gervase Mangwana  35:49  
Yes. I don't think it was the same floor but yeah, that yeah, no notes parquet. Okay. Yeah, I done actually kind of gym floor for previous friend do was that I did the building thing. In Manchester for his in his bar in Manchester. We put gym floor down there and didn't get rid of the lines. feature of the floor. Yeah. Yeah, it was that was real fun. I really enjoyed doing that. I was easy. Like, you're just like, buying it nail it lovely. Yeah, yeah, about it. Really super easy. Yeah, so So there's like a lot of elements about the house, you know, we in order to get it to enter fit, you've got to go pretty hard. So it's got eight inches of squat, 200 mil EPS all the way around. We had to do a mega job on the roof had to be it had reroof anyway retile. But it needed a lot of adjustment rafters needed extending. But that gave us an opportunity on the cavity to do details. A lot of the details around the junctions, which are the really tricky bits in retrofit. So getting eight inches of external wall insulation to somehow meet 400 mil of warm cell insulation in the loft, in a way that is bridge free effectively is is is difficult. And now we're doing I'm doing retrofit involved with mass retrofit schemes. You know, loosely in some, in some cases, social housing stuff that we're doing that that is a really challenging stuff. And when you're doing a one off and you're kind of throwing everything at it, it's not so difficult, but we came up with a word really with detail I'm really proud of that. To deal with that and to tie in the air tightness and everything but it also meant that we could cap the cavity because that's another big problem with external wall insulation and cavity wall insulation is making sure they haven't got thermal bypass in the wall. So you've got to make sure that there's no air getting into the top of the cavity. So all of this was was worked out and we've got really nice detailing on that. But that's all in kind of you know, I've got polystyrene bead, put into the tops of the walls, I've got it all filled up put in to fill the chimney up as well. So that's that's you know, it's nasty stuff, but it performs really well it's got really good moisture profile as long as it doesn't get you know sopping wet compared with like blown mirror wall which is what is existing in the rules. And then you know, I wanted some nice features inside and we've got a huge tree we were cutting one but a new tree that got well out of hands for quite a lot was getting cut down and I knew a green woodworker and he made a beautiful Bannister for us out of the out of a bent piece of view that I found I was like I think this can be think this can be a staircase so Silver's like, yeah, I can make that silver. Yeah. So but so you probably met silver and Ed's.

Jeffrey Hart  38:45  
I didn't actually I met him randomly on a straw bale building course in South Wales. Oh, right. Yep. But yes, I was instantly charmed by him. A one. Yes. He's

Gervase Mangwana  38:57  
instantly charming. Yeah. Very good friend of mine. I love him very dearly. Yeah. And he's actually it was I was talking to you recently was asking you about a tiny home. Yes. Yeah. Trailer. Yeah. That's Sylvan. Yeah. So as is still Vance is is currently designing his is quite a large trailer actually. I think compared to yours. 40 foot it's a 40 foot trailer that is owned. flatbed metal flatbed. Yeah. He's got three children. So yeah, so he's, yeah. So as I said, a lovely little project actually, because I'm obviously membranes, mechanical ventilation, you know, this kind of pragmatic approach. I love my own materials, but I pick and choose and I also like, very high performance. And I yeah, I am probably a bit shy of doing embodied carbon calculations or certainly was when I was doing this during this place. And Yeah, he's doing he's not using any types. He's not using any dunk. Yeah. So it's pretty much all Woodfibre have talked him into warm sell in places

Jeffrey Hart  40:11  
that that was it because you were asking my advice when you and I said, Oh, yeah, I went tape and NBA. Yeah, yeah, yeah, I've gone that route.

Gervase Mangwana  40:21  
Yeah. So I'm not sure where we're up to with ventilation within. But it's really nice that we're, it's an example of actually the what we were talking about before, just before we came on to recording, I think, to people who have, I guess we don't have extreme, not extremely polar. least not on the building sort of matter. But we definitely have different opinions about things. And we have to kind of negotiate that. But it's really nice that we were able to find a way to collaborate on something where we don't, we definitely probably wouldn't have the same approach. You know, he came to me and said, Look, I don't really know that much about this stuff. I know that you do, but I want to do it this way. And I'm really open to you sort of saying, you're just not going to be able to or whatever. Let's, but you know that in itself, then. Okay, right? Well, I kind of go the extra mile for this guy, and let's find a way for it to work the way that he wants to do you know, so I've gone out there and gone like, okay, you know, to all my Willie mates can sort of say that. Okay, well, we really want to actually go as Willy as we can if Sylvan. And we've, you know, we've come up with something that hopefully will, you know, will work well. It's great. It's a lovely little project. There's so nice, tiny things. I mean, it's kind of new build as well, although there is the flat better to work around. It's got lovely limitations, isn't it? It's really nice, because the invitations,

Jeffrey Hart  41:41  
I don't know if I would say they were lovely. Or a headache. But then yeah, as you say, it is nice to have strict, constrained thing to work to is. I mean, I complained about it. But it is, in many ways better than having blue sky to sort of get overwhelmed by

Gervase Mangwana  42:02  
I think this is one of the things that I love about retrofit, actually, because I just have the kind of mind that I do not find choice liberating. I can't go into supermarkets. Unless I've got a very distinct list. Yeah, I in fact, I when I had my music studio in, in London, I think this isn't a false memory. It might be a memory that I have a joke that I made about it. But I used it was a while where I was so down on my life that I was living in my studio, it was literally my that was my home as well as my studio. I had one key in my life. That wasn't rain. I used to go to the Sainsbury's off the road and my champion. And I remember going in there once. It's an hour, remember anyway, I went in there to go and get my dinner. And so repulsive was the experience that I came out without anything. Because I just I just was over faced with the with the choice and yeah, it was just too much. So I kind of I like shut myself down. In choice making, because there was too much of it. My brain doesn't work well with that. So I think that's why one of the reasons why I'm drawn to retrofit because it is inherently limited. It's inherently your there's really there's a there's a framework that you have to work with him. Yeah, give me a totally blank canvas. Albeit you've got plot maybe and you've maybe got I suppose if you've got an outline drawing, but yeah, I think I'd I mean, it's gonna be mild chest pain. So, yeah, so I do like that about rich of it. That it's yeah, it's stuff that's there. That's to work on. So yeah, where we're at, we're somewhere in the middle of the house or

Jeffrey Hart  43:40  
area. We were you talking about the bannisters?

Gervase Mangwana  43:43  
Yeah, so talking about it. So there's that and then we, you know, as I'm sort of saying the kind of the brown, green, whatever washing that we've done here. So although we use the air tightness layer here is the on the walls, at least is the internal render. Okay. So it's an it's a cement, santiment render. And all of this stuff was mostly checked. So it's EPS on the outside sand and cement on the inside. And it's the sort of, you know, Nick Parsons. I don't know Nick Parsons. Yeah. Yeah. So he's, he's very willing to at Sheffield, sustainable building, Sheffield has been doing retrofits since before it was a word I think, probably. In fact, I think he's joking. He says he's now on the third phase, those retrofit of his own home. You know, he's taking stuff out that he did the first time kind of grinding mill of EPs, or whatever it was then, but he's, he's a Woodfibre lime kind of guy. And he came up with my place in Manchester and he helped me out on a couple of other jobs up there, but his is he's a sounding board for common sense and we use each other and I'm very, very honoured that he kind of usually up to for the same purpose so that you can think through problems, rather than the being definitive answers. In retrofit. Almost always this is about moisture, always, almost always. And so that's what we're talking about, because that's the thing that scares the willies out of this. Yeah. In other people's homes. It's a different conversation when you're doing it for yourself. Yes. But it's no same conversation. But the, the risk aversion is, is slightly less because you're taking it for yourself.

Jeffrey Hart  45:29  
Yes. And there's certain things where you're willing to be a bit of a guinea pig, if you want to try something. Yeah. Whereas you wouldn't do that to someone else's production. Yeah.

Gervase Mangwana  45:43  
So yeah, so I had those kind of conversations with various different people. This is generally how I work is I have conversations with people rather than going out and getting with the models even, you know, I will see I don't actually know what that will C stands for.

Jeffrey Hart  45:56  
Oh, I don't know that. It's probably German.

Gervase Mangwana  45:59  
But anyway, it's it's sort of the go to moisture, two dimensional moisture modelling software that's quite expensive to get, like I did have one done for the one in Manchester, actually. But yeah, it's generally how if you feel like there's a risk that's big enough to check, you generally get a check for the wealthy. You get somebody like greengage, who will see for you. Yeah. So yeah, I've been through all of that here. And we ended up in what I would didn't imagine I was going to end up in, which is cement Sander render on the inside, as an air tightness layer and a bunch of petrochemicals on the outside, you know, he started out thinking that it was going to be doing nice, fully Woodfibre and probably lying. In fact, at one point I was imagining doing dialaflight on the on, you know, now internal wall installation, and they've even thought about doing it externally on the other ones, we'd have ended up with a very different performance, you know, it would have been much less well insulated.

Jeffrey Hart  46:58  
So you wouldn't have been able to get any of it. Presumably, well, not without some pretty serious thicknesses.

Gervase Mangwana  47:05  
It just wouldn't be practical. Yeah. Or cost effective.

Jeffrey Hart  47:08  
Yeah. Oh, do you feel like Oh, yeah. Do you feel happy with

Gervase Mangwana  47:13  
the choice? Yeah. Yeah, no, I do. Yeah. But I'm very when I remembered what an ex girlfriend once said, This, to me is like, once you've decided what you're doing, you're almost always happy with it. And it was an interesting observation. Because about you know, something, some people having an insight into you that you kind of thought of at all, mostly because you think that's how everybody is, you just kind of sometimes you just assume if you haven't thought about it, you assume that how you are is I now I'm much more aware that that is not the case. Thankfully, for the world, probably. But yeah, you know, I kind of yeah, there's there's things, there's definitely things I do differently, but generally as the overall approach. Yeah, I'm very happy with it. We love it as a home in general. And Tanya, my wife has many misgivings about the kind of complexity of the technology involved in the basically the heating systems really, which, which will change in time, we didn't put a heat pump in that time, I didn't have confidence in them. And it was one thing too many for me to get my head round. At the time, we were just having, classically having second child during the during the we weren't living in inherited at the time I was coming down here and back up. So it was pretty, it was a pretty stressful year and a half getting it done. But yeah, so it was on. We don't have mains gas here. So it was on bulk LPG at the time. And I didn't really want to keep it on that I knew I didn't want to keep it on that. So I wanted to get the demand as low as possible, hence the benefit. And I know we've been heating it with direct electric. So we have a massive thermal store, which has got three immersion heaters in it. We use octopus, we were on agile until that went silly. And now we're on go. So I get very, very cheap nighttime electricity, we've now got electric cars, we've got a house battery, we've got PV. But you know, I stress that all the other stuff first, obviously. And all that works really well like so my import is very low and I pay naphthol for my for my energy because almost all my energy is is five per night 5pm At night. You know, I can manage to get it all off that but it is a bit of a headache to manage. i It's quite it's quite manual. Yeah.

Jeffrey Hart  49:29  
I think that's probably one of the the reservations about going sort of full Passivhaus. And is is the technology, you know, being able to use the technology. Yeah, and I think I think

Gervase Mangwana  49:43  
I think all the others would say, you know, don't don't do what you always did. Well, you know, mvhr is for me in the HR HR has actually changed my life. So I think it's kind of fundamentally changed my life in a way that I hadn't anticipated so we put it in in the house in Manchester which I you know like i said i we moved over the road to a house that was identical to it was in 1960s length detached 80 square metres small little three bedroom, lots of them in the same area kind of thing. And I very much did it on a shoestring didn't even take the window frames out upstairs. You know, just put new units into them. Did it very much on the cheap used loads of very cheap labour labour, designed it all myself, made some mistakes especially about overheating didn't really think about the overheating but managed to get an air tightness point seven, five and put in a cheap vent Axia mvhr wouldn't say cheap and cheap the mvhr Yeah, but whole house you know, yeah. And I've always suffered in my life, I'd always suffered really, really badly from an allergy of some sort or another. And it mostly seemed to be around dust although animal animal hair was it was definitely a trigger as well. But dust would be a big thing and come the heating season. I could be triggered off and spend two days just sneezing and my nose running pretty much like brine. You know, it wasn't like wasn't mucus, it was just just streaming water out of me, which is horribly dehydrated. Just horribly uncomfortable. Just constantly like, Wait, waiting, snotty hankies. And, and it just, it just went, and I don't, I almost don't get it at all ever anymore. Even if I'm exposed to things that triggered me elsewhere. It doesn't really happen anymore. I was basically cured of a of a lifelong condition, which was, which I put up with, but was was actually pretty debilitating.

Jeffrey Hart  51:48  
So that's that's, you'd say that's because you're just getting fresh air. Now,

Gervase Mangwana  51:55  
I don't know to what extent is due to the air quality, and to what extent is due to much balanced, much better balanced relative humidity. And I suspect it's as much the latter and so it might not just be about mvhr It might be about more even heating. So not needing to have. So it would happen when the radiators would come on. You know there's that kind of you get cold air comes in, it's very dry for your house, we got down to point seven, five, it previously had an air tightness of 13 and 14 or something like that, you know, it was it was a man with it had cavity walls on the side. And the front and back were kind of curtain walls, it was a steel halfway across the middle. And then there was this sort of block work behind plastic cladding above it. When so when we take in the plastic cladding off the front, and the back of the house, and we taken all the rooms out upstairs, we ripped it out, you could actually see through the block work all the way through the house. So airtight it was not. So when that when that's in the winter, when the air outside is cold, it might be cold and wet, but it's cold and wet because it's cold. And when that comes inside, and you comes in right up against the radiators, because they're on the outside walls, and there are 80 degrees or 70 degrees or whatever it is, that air suddenly gets very dry. Yeah. So that might have been a bit of a factor as well. But again, that's, that's another thing that you get with mvhr. So I like to put it down to mvhr. It's a nice narrative to me. And I don't think it is not a particularly complicated technology mvhr I guess if you don't know, you have to change the filters. That's really important. But other than that, it can be set up in a way where it should just work by itself. And heating, heating can be done by any method really can't it. I think there's a bit of a struggle at the moment, in in a way in that. passive houses are almost too low energy for heat pumps to do to find heat pumps that can kind of cope area and work efficiently. Yeah, that might be slightly controversial. But yeah, I mean this, this house, this is 167 phpp square metres floor area. So it's actually in a sap sense. It's more like 100 and 180. It's a big house and a peak heat loss. So, you know, worst condition heat loss is barely two kilowatts, two kilowatts, something like that. So at the coldest time, the whole house only needs to take two kilowatts to keep it up. Now, the smallest air to water heat pump that you can get is five kilowatts, and they say they modulate down to 30%. So, that's You know, not, you know, that's not much less than two kilowatts, and most of the time, two kilowatts is way more than you need. Yeah. So, you know, just by those, I don't know if you followed those that simple kind of reasoning, but yes, yeah. You know, so it's never likely to be wanting to work at full capacity. So yeah, I'm in the process of kind of designing a system for the heat pump to come in at the moment. And we're still I'm still going to use the thermal store that we've got, which is quite large. So but I've been I've been advised don't heat off the thermal store. Just run the heat pump stupidly low temperature into the underfloor heating. We don't currently up to the winter heat the upstairs of this house at all. Same with water Manchester has kind of been the strategies we put the tails in for the radiators within we never put the radiators in. And yeah, I might change that. So that's, that's one of the things that I think I've been I might do differently. I don't really like radiators, they take up space.

Jeffrey Hart  55:59  
They're not particularly beautiful things. They're not

Gervase Mangwana  56:01  
particularly beautiful. No. And you know, and once you've put them there, you can't really move them, you know, so it's like you can't change your mind. You just build a house so you don't know how you're going to use it. You can't you can't talk all right, and we're going to put the radiators over there now. Yeah. But what I'm looking at as a system where I can, because almost all the supply air for the mvhr is is upstairs or one room the room I'm in now which is north facing in my study so I wouldn't own be in a bit warmer anyway. So I'm going to put a bit of heat into the supplier of the.

Jeffrey Hart  56:45  
Many thanks to Gervais for sharing his knowledge and experience. I'll be releasing part two of this chat very soon. So keep your eyes peeled. That's a weird phrase. reminder that the Patreon competition is open until the end of August when you sell for packed basket. photos on social media. And if you're listening but can't support for whatever reason, then please take a moment to share this podcast to your networks. It would absolutely make my day. Okay back with Part Two soon. See you later.


Gervase MangwanaProfile Photo

Gervase Mangwana

Low energy, Retrofit, airtesting, monitoring, ventilation, Passivhaus. Keen to learn and teach. Reformed global Dj and huge bird lover