Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

Buy individually or both books together. Delivery is free!


widget @ surfing-waves.com




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthorKenny_M
    • CommentTimeFeb 2nd 2018
     
    Masons arrived today to start work on the sandstone chimney which is being completely rebuilt. I've been quoted £6k for this work, but it needs to be done as there is water ingress and years of cement patches that are not going to get any better. Part of that cost is £1200 for scaffolding, so while the scaffold is up I really need to make a decision on what to do with the render on that gable.

    It looks like about £1k to remove the existing render which is cement based. The base coat is fairly solidly stuck on, but the outer roughcast is hanging off and needs to be removed. Cement render on sandstone is also known to prevent the natural breathing of the walls, leaving them damp and conductive, which is another reason for getting it off.

    Option 1: Is to simply tidy and repoint the wall for which he has estimated £2,400. So the cheapest option available.

    Option 2: Is to remove the cement and re-render in lime, and this probably sets me back about £3500 in total. I don’t really see the point of this, unless of course the original stone below is in too bad a condition to leave exposed.

    None of this improves the insulation of the wall, which is why I have been looking into insulated render and asking about this on the other threads and leads me to option 3:

    Option 3: Diathonite Evolution seems to have the best thermal conductivity (0.045) of the available breathable, insulated renders. 50mm of this stuff would give me a decent improvement but that is about as thick as I could make it for various reasons discussed on other threads. However, the main problem with this stuff is getting someone to do it, and although I have had a quote of around £4500 for that gable, the nearest contractor is hundreds of miles away and with travel/subsidence this quote would get higher, and I have a feeling it would need a lead flashing along the top which is probably going to mean another grand or so.

    So, in summary on top of the work that needs to be done anyway, I am probably looking at a minimum of £2k, and probably more likely £3-4 to insulate one gable wall. When I consider that of the 5 rooms that are on this gable end, 2 are spare bedrooms that are rarely used and so rarely heated, one is a bedroom that is never heated to more than 10-15 degrees, and only the two downstairs ones are used with any regularity - which means some evenings and weekends, I am starting to wonder if I would be better insulating the rooms that are actually used with internal insulation. The internal area of the walls of these two rooms are around 8m2.

    I haven't really researched internal insulation yet. I may be limited to around 50mm internally due to internal features. Old house so it needs to be breathable and I have read that aerogel is breathable and can go on the hard, but this is crazy expensive.

    Sorry for the long ramble, but wondered if anyone has experience of breathable internal insulation or has a view on which is the better way to go?

    One important point is that due to conservation area rules I can never cover the exterior of the house, and this is the north facing wall, so all the north facing rooms would still need to be insulated internally on one wall.
    • CommentAuthordelprado
    • CommentTimeFeb 2nd 2018
     
    Im thinking of Diathonite too. I think any good plasterer could use it, though, I dont think it needs a specialist. Especialyl a plasterer experienced in working with lime (which isnt rocket science either, at last for NHL, which is what Diathonite is). Spray the hell out of walls with water, dont work on a hot day, and crack on! (pardon, hopefully, the pun)
    • CommentAuthorKenny_M
    • CommentTimeFeb 2nd 2018
     
    The suppliers say that any good plasterer could use it, but most that I speak to don't seem very keen. I think that the traditional lime based guys are understandably cautious of using non traditional materials, while the modern guys are only used to using sand and cement - and some of them look at me like I am crazy when I say that the wall needs to "breathe" :)

    I posted on the plasterers forum to see if anyone had used Diathonite/Bauwer/Baumit etc, and there was only one person who knew someone who had used and said it was a nightmare to work with and a poor finish.
  1.  
    If you have render on the wall that has to be removed - why not replace it with standard EWI. That is 50mm EPS with thin coat acrylic render over. (Lots of finishes and a multitude of colours). You get a breathable insulation that is a bit better insulator than Diathonite Evolution (0.037 vs. 0.045) and is well known by builders so should be within their comfort zone and should be cheaper to install.
  2.  
    Even better, Graphite EPS is 0.032W/mK.
    • CommentAuthorgyrogear
    • CommentTimeFeb 2nd 2018
     
    Posted By: Peter_in_HungaryIf you have render on the wall that has to be removed - why not replace it with standard EWI.


    +1

    I have friends that just spent a fortune, rendering a large gable wall; they could not afford EWI...

    When I explained that they will in any case be *PAYING* for the cost of the EWI for years to come, whether they have it or not, they looked somewhat gob-smacked...

    gg
    • CommentAuthortony
    • CommentTimeFeb 2nd 2018
     
    +2
    • CommentAuthorKenny_M
    • CommentTimeFeb 2nd 2018
     
    Is EPS breathable?

    From an English Heritage research report I have just been reading "Both PIR and EPS are impermeable, plastic-based insulants"

    I would say that if I take the current render off I don't plan to re-render if I can help it. My preferred option sans EWI is to simply repoint and put the wall back to it's original condition.

    If I fitted EWI boards I would need to level the wall first as its not a level surface. I would also need something to cover the top I presume, that would mean extending the roof or some kind of flashing. All of this would add to the cost and the complications in getting planning permission (conservation area). Some of this is also true of insulated render, but probably to a lesser extent as the render could be tapered towards the edges, and would fit the form of the original wall so no need to level it before application.

    Just to be clear, I am not considering 'not' insulating, I am just starting to wonder whether the money would be better spent insulating on the inside. Especially as the north facing wall cannot be insulated externally.
    • CommentAuthorTimSmall
    • CommentTimeFeb 2nd 2018
     
    EPS has approximately the same vapour permiability as wood (as does PIR without foil facings).
    • CommentAuthorKenny_M
    • CommentTimeFeb 2nd 2018
     
    I'll admit I am a bit confused by all of this. Obviously there will be degrees of vapour permeability, but I did a bit of searching around and according to Jablite's data sheets EPS has a "significant resistance to the passage of water vapour". On another site it was classified as "semi permeable", but again there is clearly going to be degrees between semi permeable and and permeable.

    Another site suggested a WVT of 1-2 for EPS, and Diathonite's spec says 14, so EPS a lot less breathable by this reckoning.

    I'm working on an understanding that old stone walls are supposed to breathe, in particular through the lime based mortar joints and this was part of my thinking behind taking the cement off in the first place. One of the attractions of Diathonite was its high vapour permeability.

    Even if EPS is appropriate, I don't think I would get it past the planning department, a natural, lime based render might have had more of a chance, especially as it could be tapered off at the front and the top so might not look so stark against the bare Ashlar sandstone at the front.
    •  
      CommentAuthordjh
    • CommentTimeFeb 3rd 2018
     
    What is WVT? (wikipedia doesn't know)

    The plannng department has no say or interest in EPS or not. All they care about is the appearance of whatever covers it.

    The 'traditional' lime guys around me are very happy to experiment and use new materials, because they have to adapt modern materials to a whole host of different traditional situations (not many are too interested in mixing in cow manure or ox blood!).
    • CommentAuthortony
    • CommentTimeFeb 3rd 2018
     
    Water Vapour Transmission
    • CommentAuthortony
    • CommentTimeFeb 3rd 2018
     
    In my view EPS is vapour open but foam sheets like PIR without foil are not.
    • CommentAuthorKenny_M
    • CommentTimeFeb 3rd 2018
     
    As Tony says, Water Vapour Transmission, not something I will pretend to know much about, but I was looking for a value for permeability or breathability that was on the spec for both EPS and Diathonite and this was what I found. It seems it is a bit more complex than that and there are different measures for different kinds of vapour transmission. What does seem obvious is that there are materials that are highly breathable, those that are almost completely impermeable, and those that sit in the middle. Obviously EPS is somewhere in the middle, but whether it is breathable enough for a sandstone constructed period property I don't know and that makes me cautious. In all the technical reports and research published by conservation organisations that I have read I have never heard EPS suggested as a suitable material for external insulation, and that also makes me cautious.

    The planning department here do have an interest, and a say in whether I use EPS. As a conservation area they can pretty much decide what they think is an appropriate alternative material. Their principal interest is going to be how it looks, but 50mm of EPS + render squared off against Ashlar stonework will look odd.

    A potential advantage of the Diathonite is that it can be tapered off at the edges, it will fill around the contours of the original stone, and with no fixings there is no thermal bridging. I could also add it in layers, see how it looks before continuing. On top of that it has the high breathability and the elasticity to match the original materials, and although I can't find anyone locally who has used it, I have found examples of it used on period properties to the north and south.

    I think maybe I need to start phoning around the lime based guys in a radius around me to see if I can find someone who is willing to discuss working with it.
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 3rd 2018 edited
     
    <blockquote><cite>Posted By: Kenny_M</cite>EPS is somewhere in the middle</blockquote>
    True - and variable in different reports. But def OK in say a new 'breathable' wall build-up, which is likely to include for instance OSB, which is equally 'middle and variable'.

    Anyway it's a world away from cement render, which is not only highly absorbent of liquid water via its network of capillary cracks, but also usually (but not always) more or less impermeable against re-evaporation.

    If conservation advice fails to mention EPS as suitable facing, that's prob more to do with purist ideology, and I'll bet there's no alternative insulation type that is recommended.

    It's true that EWI does create detailing problems that can be unsightly anywhere, and utterly verboten in Listed/Conservation work. So yes, how would you treat the corners, if only doing an isolated gable end? Not to say neat solutions can't be found.

    But yes again, 'thick' render like Diathonite has a chance to be craftily tapered off to the verge and to leave those corner stones exposed on the gable face (tho creates an insulation weak point), even softly tapering to nothing if the corner stones are flush, a bit like http://www.repointer58.com/siteimages/photo011%20(640x480).jpg (but in reverse - can't believe I can't find a gd pic).

    Mind you, removal of cement render and knowlegeably done repointing will make that gable a lot drier, after a couple of summers, and therefore less lossy, less mould-prone.

    Worth a close study of Permitted Development rules
    http://www.legislation.gov.uk/uksi/2015/596/pdfs/uksi_20150596_en.pdf (see Part 1 on p13, and read all the rest in that light)
    https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/606669/170405_Householder_Technical_Guidance__-April_2017_FINAL.pdf (see esp p33)

    A lot depends on whether your LA classes EWI as 'cladding' or 'over-cladding', or as simply replacement of existing render.
  3.  
    ''It's true that EWI does create detailing problems that can be unsightly anywhere, and utterly verboten in Listed/Conservation work. So yes, how would you treat the corners, if only doing an isolated gable end? Not to say neat solutions can't be found. But yes again, 'thick' render like Diathonite has a chance to be craftily tapered off to those vertical corners, and verge.''

    For the even less pure non-purist, there's the possibility of an amalgam - for example the majority done in EPS EWI, with tapered edges done in (meshed) Diathonite or similar.
  4.  
    EPS has been used for over 30 years in Germany and there are studies that show no degradation over that time. There are also studies that show that EPS performs better below ground that the often quoted XPS needed for below ground applications.

    There is no reason why EPS has to be installed with a square edge. It would be an easy job to taper or round off the edges either once the ESP is up and before rendering or before placing the edge sheet on the wall.

    I have insulated a stone / rubble wall with EPS without problems. The stone work (basalt rock) was not too flat and the choice was to render flat first or use a thicker layer of adhesive to take up the difference. I calculated that a thicker amount of adhesive would be cheaper. The method used was to put a thick line of adhesive top and bottom of the sheets with 4 good dollops in the middle, the sheet was then pressed onto the wall as far as it would go or to give a reasonable fit to the adjacent sheet. Once the wall was finished the whole lot was sanded (with the tool made for the purpose) to take out any protruding edges prior to rendering. This worked well, the insulated wall is still not flat but has gentle undulations when you look down the wall. (it is 36M long).

    Apart form the obvious the reason I insulated the wall (north facing) was because I have tenants in the house and one room, which they did not use much and only heated when needed was getting black mould all over the wall. They washed the wall with bleach but 2 weeks later the mould was back. 100mm of EPS insulation on the outside fixed the problem! It is now the 3rd winter with the insulation in place and there have been no problems. In fact I only insulated the problem area to start with and this solved the problem so last summer I insulated the rest of the building to match.
    • CommentAuthorKenny_M
    • CommentTimeFeb 3rd 2018
     
    Tom - I'm not able to see the pic you posted - it just keep bringing up an error. Was interested to see this if you don't mind posting again.

    I'm in Scotland so the regs you posted don't apply (but thanks just the same), and the equivalent regs here don't really apply either because as a conservation area I have to make a householder application for any change to the outside of the house, and the council make a consulted judgement on whether to approve. I spoke to a planning officer and I can apply to fit EWI, but he did express doubt over how it would look from the front of the house so I wouldn't be too hopeful.
    • CommentAuthorgyrogear
    • CommentTimeFeb 3rd 2018 edited
     
    Posted By: Peter_in_HungaryEPS has been used for over 30 years in Germany and there are studies that show no degradation over that time.


    I'm in France, and have 50mm EPS EWI on a 1983 construction.
    Got a chance to examine it in detail 2 yrs ago during installation of new windows, looked as good as new.
    It's true I have a few minor repairs (cosmetic) to address on the rendering in places...
    (in fact it is not rendering, but extremely hard cement board, with a sort of Artex facade paint).

    gg
  5.  
    Posted By: Kenny_MI spoke to a planning officer and I can apply to fit EWI, but he did express doubt over how it would look from the front of the house so I wouldn't be too hopeful.

    If the corners are 'feathered in' so that there is no protruding square corner obvious I don't see that it would look much different to the render that is already there - except or course perhaps it might be in better order than the existing. - unless you choose a pale purple colour or similar for the top coat
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 3rd 2018
     
    Posted By: Kenny_MI'm not able to see the pic you posted - it just keep bringing up an error. Was interested to see this if you don't mind posting again.
    I couldn't get it to 'underline' the whole - just copy/paste it into a new tab.
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 3rd 2018 edited
     
    Posted By: Peter_in_Hungaryunless you choose a pale purple colour
    believe it!
      P1000822 med.JPG
    • CommentAuthorgyrogear
    • CommentTimeFeb 3rd 2018
     
    yeurrk !

    perhaps it was the bedroom wall of the neighbouring property forcibly demolished in the meantime...
    :shamed:

    gg
    •  
      CommentAuthordjh
    • CommentTimeFeb 3rd 2018
     
    Posted By: Kenny_MThe planning department here do have an interest, and a say in whether I use EPS. As a conservation area they can pretty much decide what they think is an appropriate alternative material.

    Ah, I'm interested in how Scottish rules differ. Could you post a link to a document that explains how your planning controls insulation material choice, please?

    In England there's a clear distinction between planning and building regs and a separation of concerns.
    • CommentAuthorKenny_M
    • CommentTimeFeb 4th 2018
     
    djh - its the same here, but being in a conservation area changes everything. As far as I am aware there is no document as such covering what can and can't be done in this area. I've asked about this before and they just direct you towards submitting a householder application. What I have been told is that like for like repairs are fine, but anything that involves a change in materials being used requires an application. I know for example that they won't approve PVC frames for double glazing, and they are fussy about the type of glass that is used. I agree that with EWI its more how it looks that they will be concerned with. I'd have to do some drawings to convince them.

    Tom - I see the pic now. Yes, this is what I was thinking about, in reverse as you say.

    Peter - Interesting to know that you insulated a stone built house with EPS. I don't know how the permeability of Basalt compares to sandstone, although from the bits of the old render I have taken off so far it looks like my wall on the side is actually a mix of sandstone and whinstone. I think in at the time of construction Ashlar Sandstone would have been very expensive and only put on the front, with the sides made from cheaper rough cuts of local stone.

    I don't see the weak point in the insulation being a big problem because where it tapers off to the side will be after the point where the uninsulated front wall begins , as they are around 600mm thick. Where it tapers off at the top will be at the roof, so also beyond the point of the heated part of the inside wall. On the gable I am talking about there is a drainpipe which would help to disguise the tapered end. However, on the other gable I have a bigger problem, the fact that this wall borders the next property, so any protruding insulation would be protruding into their space. They are pretty reasonable so would probably be ok, but its another consideration.

    There remains the issue that the coldest wall (north facing) will be the one I can't insulate from the outside and I would have thought this would then become a condensation risk. I can of course insulate that wall from the inside, but then I am back to thinking if I am going to insulate one wall from the inside, would I be as well to just insulate all the walls on the inside and have a uniform insulation in the walls.

    The other thing I keep thinking about is the chimney stack on the gable. 3 of the 4 flues are unused, so it means that I would be insulating the outside and a ventilated cavity in the middle.

    I think all of this needs a bit of planning and I might be better not to jump in now unprepared just because I have a scaffold up. It might be good, as Tom says to let the wall breathe for a bit after getting the cement off, and ensure all the dampness issues are resolved before doing anything more. I actually think the leaky chimney has been the main problem but it will be some time after this is fixed before I can confirm that. Given the limited funds I have available its probably also better to direct these towards CWI in the extension, new condensing boiler, upgrading the glazing etc.

    This discussion has given me plenty to think about so thanks all for your comments.
    • CommentAuthorKenny_M
    • CommentTimeFeb 4th 2018
     
    Completely unrelated to the thread, but I just broke into the original fireplace on the wall being discussed - pic below. Going to get a liner down while the scaffold is up, and add a stove at a later date.

    https://www.dropbox.com/s/m8b924hufxs9hvw/2018-02-04%2014.23.20.jpg?dl=0
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 5th 2018 edited
     
    deleted - mis-posted
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 5th 2018 edited
     
    Posted By: Kenny_MTom says to let the wall breathe for a bit after getting the cement off
    Not necessarily - breatheable EWI can go ahead immediately. I said it would dry in time anyway, after render removal, essentially incl gd repointing, if it's to be left bare.
  6.  
    Posted By: fostertomafter render removal, essentially incl gd repointing, if it's to be left bare.

    If it is to be left bare for any length of time and it matches the front then it might be the devils own job to get the CO to agree to re-rendering. Get agreement to re-render in writing before the works start.
    • CommentAuthorKenny_M
    • CommentTimeFeb 5th 2018
     
    Tom, by "breathable EWI" do you mean EPS or a natural insulation like the Diathonite/wood fibre etc? I am still not clear on whether vapour open and breathable are the same thing, or if EPS is breathable in the way that is normally meant when talking about lime mortar/wood fibre etc?

    Peter - not sure what CO means, presuming compliance officer, called a planner officer here. I don't plan on telling them that I have taken the render off, so that I can keep my options open. In the highly unlikely even that they notice, I will just say that it is work in progress and I am preparing to re-render once it has dried out. They can't stop me from re-rendering, but they could object to the thickess required for insulation.

    I am still not sure about the logic of having the gable wall heavily insulated while the north facing front is completely uninsulated. This might not meet the definition of a thermal bridge, but maybe a thermal 6 lane highway! :) Is this not inviting problems with condensation? To have a warm insulated wall, with the insulation tapering off to a cold corner. I am sure I read on one of the other threads that corners were prime areas for thermal bridges and condensation. Even if I insulate the north wall on the inside, I presume there will still be a path through the wall at the corner that cannot be insulated.

    The decision might be taken out of my hands anyway as the money is running out for this year. By the time the ever increasing bill for the chimney is finalised I will have limited amount left. I will save a lot more energy by getting a condensing boiler, CWI and new glazing in the extension, than I will be losing through that one gable wall, for about the same money so they would be the priority.
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press