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    • CommentAuthorKenny_M
    • CommentTimeApr 30th 2018
     
    I commented on Delprado's bathroom insulation post earlier, but thought it might be better to create a new thread for this. While I love the tea cosy idea of external insulation, as I have mentioned in other threads it's probably not an option for me.

    Due to various issues/plumbing leaks etc, prompting a might as well go the whole hog with this approach and now the bathroom has been gutted. Plumbers are going to reposition the soil pipe and rough out over the next few days but I probably only have a few days now to decide what to do with the walls. There are two external walls, one with a window, one internal stone wall lime plastered on the hard, and an internal wall with an attic stairway protruding into it.

    For the two external walls I am thinking on taking back to stone and then doing, something! I've been reading about internal insulation for years now and it seems to be a minefield with little agreement on what's best. Lots of sites seem to insist that a vapour barrier is essential, although I know on here some suggest that its better to leave the whole structure vapour permeable to a degree. The external walls are currently covered in cement render, but this is boss, so is in the process of coming off anyway, so I am wondering whether with the outside going back to its original vapour permeable state, if it makes sense to do this on the inside too.

    One thought about vapour barriers, is that a lot of the period property/conservation sites/blogs etc, rail against modern paints and gypsum plaster, which they say create an undesirable vapour barrier, if these are impermeable, is there much point having a vapour barrier as well?

    Is it still standard practice to fix a timber stud to the inside of the external wall and insulate between, or are their better ways, such as direct fix of something, or fixing the battens floor to ceiling and putting insulation behind?
    •  
      CommentAuthordjh
    • CommentTimeApr 30th 2018
     
    Posted By: Kenny_Mmodern paints and gypsum plaster, which they say create an undesirable vapour barrier

    Modern paints come in many varieties, some of which are vapour barriers and some of which are extremely permeable, and many others at all degrees in between. Gypsum plaster is quite permeable. So anybody saying it creates a vapour barrier is simply wrong.

    In amongst your consideration of insulation methods, don't forget to plan for good ventilation. In a bathroom that is absolutely essential to make the insulation solutions work.

    If you do go for a 'breathable' solution then I would personally go for as hygroscopic as I could. Maybe woodfibre insulation?

    But what are you using for the surface treatment? Most bathroom surfaces are impermeable (tiles, panels, even paints). No point going for breathable insulation if you're going to tile over the top, unless you expect the vapour drive to be inwards.
    • CommentAuthorKenny_M
    • CommentTimeApr 30th 2018
     
    Posted By: djhGypsum plaster is quite permeable. So anybody saying it creates a vapour barrier is simply wrong.

    See this is the thing that has confused me for a long time. Gypsum and modern emulsions are widely castigated as a cause of dampness in old buildings, and I can't see how gypsum could be the cause, so if there is an issue with this combination then maybe its the paint. Alternatively I wonder also if this theory is coming from the hygroscopic nature of lime versus gypsum, i.e. lime plaster soaks up water and passes it through it without too much issue, but when gypsum gets wet it tends to fall apart.

    Posted By: djhdon't forget to plan for good ventilation

    Already on the case, gonna go straight up above the shower and through the roof, with an inline fan, rather than through the 600mm thick wall. Thinking humidity sensor fan as the bathroom is bright and shower is likely to be used a lot with the light off.

    Posted By: djhBut what are you using for the surface treatment?

    I only intend to have tiles around the shower/splashbacks etc, but this comes back to my question about paint. I've found it difficult to get data on the vapour permeability of paint, and as you say there are lots of different types of paint, and although it might be fairly impermeable, its also a thin layer.

    With paint on gypsum, any gaps well sealed and the bathroom well ventilated, does the vapour permeability and hygroscopic properties of the insulation become less relevant?
    • CommentAuthortony
    • CommentTimeApr 30th 2018
     
    I would not put wood near a shower unless the design is completely fail safe, no pipes in the wall, no joins in the waterproofing systems.
    • CommentAuthorRick_M
    • CommentTimeApr 30th 2018
     
    Posted By: Kenny_MGypsum and modern emulsions are widely castigated as a cause of dampness in old buildings,


    Perhaps because the way plasterboard can be installed, ie dot and dab with gaps for air to pass through rather than the material itself? And AFAIU, a thick layer(s) of lime plaster acts as a better buffer for moisture spikes as opposed to say 12.5mm plasterboard. And woodfibre insulation acts as a buffer as well. I haven't heard of emulsion being blamed for damp problems though.

    Do the woodfibre sheet manufacturers recommend one type of plaster over another in terms of adhesion?
    •  
      CommentAuthordjh
    • CommentTimeApr 30th 2018
     
    Posted By: tonyI would not put wood near a shower unless the design is completely fail safe, no pipes in the wall, no joins in the waterproofing systems.

    Pretty much every house in the country that has studwork internal walls, even just upstairs, has this combination. That includes every house I've ever lived in and I for one have never seen any problems. Neither I suspect have the vast majority of other people.
    • CommentAuthorKenny_M
    • CommentTimeApr 30th 2018
     
    Couple of pics

    This shows the protrusion of the attic stairway. This was all boxed out in plasterboard and the entire window was boxed out so you couldn't see any of the original window panelling.
    https://www.dropbox.com/s/yobcjs4mll29s9d/2018-04-30%2017.28.49.jpg?dl=0

    This is the main external wall that I plan to insulate after the frame and modern plasterboard removed. Pulling some more off since taking this pic shows that there was original plaster directly applied to stone, which must have later been covered over with lath and plaster, which later again was covered with a frame and modern plasterboard. If I rip all of this off back to stone it would give me at least 70mm to play with before the plaster would protrude past the window frame, and more if needed on the east wall.
    https://www.dropbox.com/s/v4bpnhabfun0odv/2018-04-30%2017.30.51.jpg?dl=0
  1.  
    Gypsum gets overloaded with moisture and, when contaminated with salts, becomes more hygroscopic as I understand it, and tends to get more overloaded, etc. (Though I accept there must be a peak saturation point!).
    • CommentAuthordelprado
    • CommentTimeMay 2nd 2018
     
    its not the gypsum that is the problem (although most gypsum products are not pure gypsum anyway, so in theory the vapour permeability is untested), its the PVA used behind it.

    gypsum doesnt like damp environments like in an old cottage and it just turns to mush.

    acrylic type paint is super impermeable, and only needs a very thin layer to block everything. In general its not that bad if you close up the inside using these things, the much better problem is sealing the outside, for the obvious reason that the vapour pressure usually heads from in to out and moisture travels in the same direction, and if it cant get out in stays in the wall, saturates, and comes back in again
  2.  
    After seeing the damage caused by gypsum and concrete in our old farmhouse causing damp both are now banned. Once you get into the permeable way of renovating an old stone house it becomes quite easy and as the walls dry out the insulation effect of the thick stone walls increases. As for the bathroom we used lime plasters to seal the room then a Lunos e2 MVHR unit to control the humidity in the room with electric UFH on 50mm insulation to heat the room together with an electric towel rail.
    • CommentAuthorKenny_M
    • CommentTimeMay 2nd 2018
     
    Another pic now that I am down to the bare stone. Looks like there has been an original fireplace, then made smaller and a 'new' Lintel added at some point in the history of the house.

    https://www.dropbox.com/s/t6tyfft3iu8oifx/2018-05-02%2007.51.04.jpg?dl=0

    So, would it be reasonable to consider insulation boards direct to the wall, then a wooden frame fixed to the floor and ceiling joists, on the warm side to hold the insulation to the wall and fix the plasterboard on the other side, then paint to at least limit the vapour diffusion? The link below has a diagram at the top of the page that seems to be similar to what I am suggesting:

    http://www.superhomes.org.uk/resources/internal-wall-insulation-1/

    The question for me is what insulation type. The link suggests P/U foam. Even though I am attempting to keep the vapour bathroom from the insulation, would it still make sense to go breathable, allow any small amounts of moisture to find their own way through the structure?
    • CommentAuthorgyrogear
    • CommentTimeMay 2nd 2018 edited
     
    Posted By: Kenny_Mthen a wooden frame fixed to the floor and ceiling joists, on the warm side to hold the insulation to the wall and fix the plasterboard on the other side,


    If you use the right adhesive and plastic expansion anchors, no need for the timber frame.
    (No need for the PB neither - tile direct to the insulation...).
    (I personally would not in any case tile direct to PB in a wet-room, all you have holding the tiles is a thin sheet of... cardboard) :shamed:
    (the only plasterboard in my house is for fireproofing to my roof insulation and a (short) staircase soffit).

    gg
    • CommentAuthorKenny_M
    • CommentTimeMay 2nd 2018
     
    I'm not planning on tiling the room, just inside the shower cubicle. I was originally thinking of using cement board here instead of plasterboard, but I am now leaning towards wet wall instead of tiles here. The original lime plaster will remain on the internal walls, its just the external walls where the lath and plaster was damaged and has been taken down that I plan to insulate then plasterboard over.

    I've no strong feelings about using timber, but I wasn't sure how easy it would be to get everything straight as the walls are uneven stone. One thought I had had was to build the plasterboard wall as I mentioned, then fill with loose insulation, like cellulose fibre, from the attic. This would fill all the uneven surface etc, and form a continuous seam of insulation from below the floor to the attic where it would meet with the loft insulation. It would also fall in behind the old window shutter/sash box etc.
    • CommentAuthorgyrogear
    • CommentTimeMay 3rd 2018 edited
     
    OK, thanks for the extra details.

    Posted By: Kenny_Mwould it still make sense to go breathable, allow any small amounts of moisture to find their own way through the structure


    I'm no expert, but given the presence of a large opening window, can't see how or why moisture would make for the (insulated...) wall first: it surely would tend to make for the COLD window, and condense, at which point you would presumably crack the window open :devil:

    Whence my suggestion for XPS...

    You could use metal studs instead of timber, and still board with XPS.
    Then inject "crazy foam" behind the XPS, to fill the void (after adequate propping of the XPS plane).

    (either carefully estimating the quantity of foam to inject, or allowing sufficient escape routes (with soapy water...) to stop the foam from exploding the XPS and/or fixings...).

    Cheers,

    gg

    (I'm renovating my shower room as we speak, so to speak, including two wet walls ! and XPS direct to external wall. No window, just extract ventilation. Will add a small velux when I'm In The Money...).
    • CommentAuthorKenny_M
    • CommentTimeMay 3rd 2018
     
    Thanks gg for the suggestion, I will look into this, metal would work I suppose on the wall behind the insulation. In this scenario would I just bond the plasterboard to the insulation then?

    I suppose I have this thing about materials being breathable or vapour open in old houses as this is the prevailing view amongst conservation folks, and there also seems to be quite a few on this forum who also that vapour tends to get in no matter what you try to do and at least if the material is permeable it can get back out - if I am explaining that right.

    My thought was that by building a false timber wall and pouring something like thermofloc into the void, I would have a continuous seam of vapour open insulation in between the stone and the plasterboard. I am sure I heard of someone doing this with EPS before which would come to the same thing.
    • CommentAuthorgyrogear
    • CommentTimeMay 3rd 2018 edited
     
    Posted By: Kenny_MI would have a continuous seam of vapour open insulation in between the stone and the plasterboard. I am sure I heard of someone doing this with EPS before which would come to the same thing.


    Agree, EPS would work on that, you'd just have to make sure that the dew point would be far enough out, to prevent the timber from getting wet and rotting on the wall...

    As it is, the PB itself should be hygroscopic, vapour moving in and out "under its own steam"...
    The question is, how many cycles will it tolerate and how many years will it last ?

    gg
    • CommentAuthorKenny_M
    • CommentTimeMay 4th 2018
     
    Posted By: gyrogearyou'd just have to make sure that the dew point would be far enough out


    This is the thing that still confuses me about interstitial condensation. If I built a frame out from the wall fixed floor to ceiling as I was suggesting, then had insulation against the wall, or alternatively had insulation fixed direct to the wall, the dew point would presumably be in the stone wall. Would water condense internally within a sold stone wall? If it did what would be the problem, there is nothing to rot, and unless we are talking about copious amounts of water, then surely it would just pass out through the lime mortar or to the surface of the stone.

    Everything I read about internal insulation has warnings about interstitial condensation, and it has me a bit paranoid, to the point of questioning whether I should insulate at all. Given that I generally tend to keep internal humidity levels under control, and intent to ensure the inner skin is well sealed to the passage of water vapour, I wonder if I am worrying unnecessarily.

    The one thing that does have me concerned is the joist ends on the south wall where they terminate. If I don't insulate below the floor here do I risk a cold bridge and condensation, if I do insulate below the floor here do I risk making the wall where the joists terminate colder and risk condensation. There appears to be a bit of a damned if I do, damned if I don't element to this! :confused:
  3.  
    Really pleased with my Lime plastered walls on stone so long as you can find someone capable of using it. Could not find a plasterer willing or capable of doing Lime so went on a course and learnt how to do it myself. Its really easy to get flat walls once you learn the techniques even on stone walls. I am sure the MVHR system is the key element in securing the health of the bathroom.
  4.  
    Renewablejohn, I take it your lime plastered walls are not insulated? Or are they?

    Kenny_M's concerns re interstitial condensation would not apply with no insulation, and lime is obviously the best thing to manage moisture. Something like Diathonite would, subject to a condensation risk assessment, deal with the moisture and reduce heat-loss while minimising interstitial condensation risks.
    •  
      CommentAuthordjh
    • CommentTimeMay 4th 2018
     
    Posted By: Kenny_MEverything I read about internal insulation has warnings about interstitial condensation, and it has me a bit paranoid, to the point of questioning whether I should insulate at all. Given that I generally tend to keep internal humidity levels under control, and intent to ensure the inner skin is well sealed to the passage of water vapour, I wonder if I am worrying unnecessarily.

    You and me are both paranoid. Early in my journey I discovered the potential problems with renovation and internal insulation and that drove me towards a new build. There are two separate problems that you need to manage, both concerned with condensation.

    The first problem is condensation in organic materials. If you have something that can rot in a place where it can experience condensation, then rot is a concern. The simplest solution is not to put anything like that in such a situation. Which leads to rules of thumb about how to keep timber, such as joists, warm enough to prevent condensation. Otherwise, you're into calculating how much time the material will be in a condensing situation versus how often it will be drying out, either to the outside or to the inside. Things get complicated pretty quickly.

    The second problem is condensation in non-organic materials, especially stone and brick. Here the concern is not rot but freezing. If there is water inside stone or brick, typically in crevices, and it freezes then the ice exapands and can break the stone or brick ('spalling'). Clearly the moisture in this case does not have to be condensation from inside but can also be rain from outside.

    For the first problem, one of the best ways to manage it is to provide humidity buffering, using hygroscopic materials. But most (all?) hygroscopic materials are organic and can rot. So its a balancing act between extending the time before rot starts using hygroscopic materials and putting more organic material at risk. Nowadays the way to minimise risk in such situations is to use programs like WUFI to model the situation.

    For the second problem, you basically need to hope that your external wall is not liable to spalling, because IWI is going to make it cooler and thus more liable to spalling.
    • CommentAuthorKenny_M
    • CommentTimeMay 4th 2018
     
    Posted By: renewablejohnCould not find a plasterer willing or capable of doing Lime so went on a course and learnt how to do it myself.


    I found this same problem, not just with lime, but also with the insulating renders that I was looking at before like diathonite and bauwer. No one wanted to know. One of the reasons I pulled down the lath and plaster wall in this bathroom is that I knew I would struggle to find someone to repair it. Unfortunately I have no hope of being able to plaster large areas, I'm confident at turning my hand to most other things, but I am rubbish at plastering anything more than a small patch.

    Posted By: djhHere the concern is not rot but freezing. If there is water inside stone or brick, typically in crevices, and it freezes then the ice exapands and can break the stone or brick

    But surely water must pass through an old house as a matter of course, even without insulation, and as long as lime based, rather than cement mortar has been used for pointing the water should pass out through the joints? Spalling is usually due to cement pointing, on soft stone or brick that was originally lime pointed.

    Posted By: djhhumidity buffering... using hygroscopic materials

    This is one of the reasons I was considering creating a framed warm plasterboard wall out from the stone wall, then filling with cellulouse fibre (thermofloc) which I believe is hydroscopic, and would fill all the gaps avoiding the need to level the wall. As this fill would be open to the ventilated loft, I also figured this might aid vapour transmission. The thing I hadn't really considered until the last 24 hours is how it might affect the joists below the floor.
    • CommentAuthorRick_M
    • CommentTimeMay 7th 2018
     
    My understanding is that the risk to joist ends in walls can be reduced by not using more than around 60-80mm of insulation and making sure no (warm, wet) air is able to reach the ends by making things airtight. One method I've seen is to achieve this is to tape (eg Tescon) the joist ends to the wall and then plaster over that tape before insulating.

    Also, I would favour wood fibre board over cellulose here as it's much denser than cellulose (especially loose fill) so air wouldn't be able to pass through as easily (at all?) so you have a second line of defense against vapour being carried through by moving air (much more of a concern than vapour diffusing through). Also, pouring it down from the attic sounds difficult to me; would you get complete coverage, will the stud wall have noggins in the way?

    How about making the wall flat with a lime plaster then attaching wood fibre boards on top with adhesive and fixings. If no plasterer will do it you could try using battens temporarily screwed to the wall as guides so you can't go too wrong.
    • CommentAuthorKenny_M
    • CommentTimeMay 8th 2018
     
    Thanks Rick

    I am thinking now that the joists might be less of an issue than I first thought. This is a first floor bathroom and I am now thinking that maybe I only insulate from floor to ceiling. The joists below would be kept warm from the room below, and above them would be vapour open wood floor and insulation, and vapour open sandstone to the side. The joists above are in a ventilated roofspace.

    I was starting to think about wood fibre, and maybe just using some loose cellulose in the area behind the shower where there are pipes and the insulation could fit around these. I could put this in before I close the plasterboard above the shower. Your point about the density of fibreboard might well help with air coming the other way too, as a rubble brick wall is not likely to be very airtight.

    I don't think I can do a direct fix as I will need a service space for the shower pipework, so I will probably have to batten out. Maybe the simplest solution is just to batten out from the wall and put say 40mm of wood fibre between the battens.
  5.  
    ''I don't think I can do a direct fix as I will need a service space for the shower pipework, so I will probably have to batten out. Maybe the simplest solution is just to batten out from the wall and put say 40mm of wood fibre between the battens.''


    So where will the pipework be relative to the battens, then? Behind the insulation, in the cold? (In pipe-wrap)?
    • CommentAuthorKenny_M
    • CommentTimeMay 8th 2018
     
    <blockquote><cite>Posted By: Nick Parsons</cite>So where will the pipework be relative to the battens, then? Behind the insulation, in the cold? (In pipe-wrap)?</blockquote>

    I'd have try and get some insulation between the wall and the pipework, that's why I mentioned pouring cellulose fibre into that space. There is no where else for the pipework to go, the internal wall is solid too and plastered on the hard.
  6.  
    <blockquote><cite>Posted By: Nick Parsons</cite>Renewablejohn, I take it your lime plastered walls are not insulated? Or are they?

    Insulated with Hemp Lime Plaster, Could have been slightly better insulated if I had used cork lime plaster but at the time I could not source any locally.

    As for plastering I used to be rubbish using thistle plasters but lime is very forgiving and learning the techniques at Ty Mawr I surprised myself how professional it looks even doing a curved ceiling section using a new lath section.
    I did however cheat by using ready mixed tubs of lime plaster but the extra expense was well worth it.
  7.  
    Posted By: Kenny_M
    Posted By: Nick ParsonsSo where will the pipework be relative to the battens, then? Behind the insulation, in the cold? (In pipe-wrap)?


    I'd have try and get some insulation between the wall and the pipework, that's why I mentioned pouring cellulose fibre into that space. There is no where else for the pipework to go, the internal wall is solid too and plastered on the hard.


    I solved the pipework problem with solid walls by using plastic trunking as a skirting board. Trunking contains hot ,cold and waste pipes together with electrics for mirror lights.
    •  
      CommentAuthordjh
    • CommentTimeMay 9th 2018
     
    Posted By: Kenny_M
    Posted By: Nick ParsonsSo where will the pipework be relative to the battens, then? Behind the insulation, in the cold? (In pipe-wrap)?

    I'd have try and get some insulation between the wall and the pipework, that's why I mentioned pouring cellulose fibre into that space. There is no where else for the pipework to go, the internal wall is solid too and plastered on the hard.

    There are some showers that keep the plumbing on the surface, for such situations. (There is hidden plumbing above the ceiling, but the drop is exposed).
    • CommentAuthorKenny_M
    • CommentTimeMay 9th 2018
     
    Thanks guys. I think I am more or less decided. I am going to build a frame on the main wall and use wood fibre boards behind it. The frame will be on the warm side of the insulation and there will be room for services in it at the shower. The area around the old window surround will be a bit trickier but the frame will cover the main external wall.

    It would be nice idea to render directly on to boards or straight on to the wall with insulated render, but I keep coming up against the issue of getting people who can or are willing to work with something that doesn't fit into the standard practice. I have to stick with something I can do and I know I can make a frame, put plasterboard on it and make it look presentable. If I tried to plaster a whole wall on the hard it would look like a dogs dinner.
    • CommentAuthorRick_M
    • CommentTimeMay 9th 2018
     
    Insulating around the window does look like it will be tricky unless you remove the paneling for access?

    I see the reasoning behind opting for a frame but you could alternatively notch out channels for the hot and cold pipes in the fibreboard, check if standard gypsum plaster is compatible and then just get a plasterer in. Worth thinking about how the shower mixer valve will be attached to the wall.
   
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