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Thread: External insulation

  1. #1

    Default External insulation

    Can anybody help?! I live in an old house with single skin walls which I want to get externally insulated. I have looked online to try and get some idea of what product to use, how to manage door/window reveals, roof line extension and so on. I seem to be getting nowhere.

    Anyone on here got any experience or info on this? Any help would be gratefully received.

  2. #2
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    I thing that you could look at is building an external timber frame with something like kingspan in it, and leave a 50 mm gap between walls. The new outer wall could either be timber cladded or use brick slips if you want to keep a brickwork effect.
    This would probably give you enough insulation, if not you could also go the cavity insultation way.
    I have no idea if the building regs would object to this.

    Just had another thought, if you are pushing the wall line out and you will definatly need an architect to check that the extended roof line would not interfere with the first floor window tops. It depends on pitch of roof ect.
    The roof is fully supported and could just have extensions fixed to the rafters.
    As far as the window reveals go, the windows would be removed and repositioned into the outer frame.
    Let me know how you get on as I have never heard it done this way round before.
    Might also be worth a word with the authorities as to if they have a prefered method of doing this kind of thing.
    Ratty (Russ)

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  3. #3
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    Just been looking further into the brick slip system. I have only used it on new builds.
    But it looks like you can use it on existing external walls and it can also come with insulation which would mean that there would be no requirment for a timber frame.

    Do a little research on this system and get a few prices from differant companies, if they dont give you a projected insution rating ask for one. you will need to know what the total will be when its fitted and including your current walls.

    The brick slips are usally 20mm, you will also need to know what the thickness is including insulation, any cavities and anything else they fit to make up the system. You may not even need to alter your roof if the fiquires come out good and your eaves and gables are of a reasonable depth.
    Ratty (Russ)

    I know only that what is moral is you feel good after. What is immoral is what you feel bad after.
    Ernest Hemingway

  4. #4

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    Quote Originally Posted by SandfordSailor View Post
    Can anybody help?! I live in an old house with single skin walls which I want to get externally insulated. I have looked online to try and get some idea of what product to use, how to manage door/window reveals, roof line extension and so on. I seem to be getting nowhere.

    Anyone on here got any experience or info on this? Any help would be gratefully received.

    Contact an insolation company they will be able to give you ALL the options for single skin buildings.
    This is the type of work they are doing in my area now.

    Slab foam 60 or 75 mm thick fixed to the exterior with long plastic fittings then covered in a kevlor cloth and then rendered .

  5. #5
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    I hadn't heard of external insulation. I live in a 1970s timber frame house and cavity wall insulation is not possible so this got my interest, so had a look with Google (external insulation products uk as the search term).

    I see the problem very little practical info but there are lots of manufacturer and installer sites. Maybe this is because the products and systems used are not so DIY friendly.

    Found this little video on one site.

    Planning permission issues associated with this system too and building regs. not doubt, which may account for less on the DIY front and more on trained installers etc.

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  7. #7

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    Quote Originally Posted by Quercus View Post
    I see the problem very little practical info but there are lots of manufacturer and installer sites. Maybe this is because the products and systems used are not so DIY friendly.
    This is the frustration I face. I cannot see why this would be beyond a DIY installation. I would be comfortable extending all the reveals myself and believe that fixing the insulating layer to the stone walls would be okay. I would then just need to get a renderer in.

    Adrian - thanks for the lead to Sto - I hadn't come across it. In my research I have found that it is recommended to have a vapour permeable external insulating layer to prevent moisture build up in the underlying structure. This is the first product I have found which mentions permeability.

  8. #8

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    Do you understand the concept of intersticial condensation? This is usually the potential problem to be guarded against. The problem with external insulation is that the temperature gradient falls greatest towards the inside of the building so, unless the walls can actaully warm up, there is always a possibility of dampness.

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    Quote Originally Posted by SandfordSailor View Post
    This is the frustration I face. I cannot see why this would be beyond a DIY installation. I would be comfortable extending all the reveals myself and believe that fixing the insulating layer to the stone walls would be okay. I would then just need to get a renderer in.

    Adrian - thanks for the lead to Sto - I hadn't come across it. In my research I have found that it is recommended to have a vapour permeable external insulating layer to prevent moisture build up in the underlying structure. This is the first product I have found which mentions permeability.
    Ventilation is critical.

    This any use? We used an Epsicon product about 10 years ago as it was cheaper than the Sto equivalent and AFAIK its still attached to the wall.. I don't know if the actual render is compatible with your average small builder/DIYer as we've failed to persuade smaller outfits to use it in the past. Its applied in very thin coats, allegedly flexible (less cracking) can also be self coloured.

    Is there a reason not to insulate on the inside - no weather proofing issues, no planning issues, easy DIY job and even 25mm made a huge difference to my flat. Have a dig around the Kingspan website for info.

    A

  10. #10
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    Hi. When you say you have only single skin wall, do you mean 9" (1 brick length) solid walls as used in Victorian era construction, or do you mean 4" (1 brick width) thick?

    JP

  11. #11

    Default Thanks so far . . .

    Quote Originally Posted by Adrian Cooper View Post
    Do you understand the concept of intersticial condensation? This is usually the potential problem to be guarded against. The problem with external insulation is that the temperature gradient falls greatest towards the inside of the building so, unless the walls can actaully warm up, there is always a possibility of dampness.
    Blimey Adrian - you're getting technical. My understanding of intersticial condensation is that to avoid it, you need to make sure that your external insulation layer has a higher vapour permeability than the original walls. Is that right?

    Quote Originally Posted by Davy 90 View Post
    Is there a reason not to insulate on the inside - no weather proofing issues, no planning issues, easy DIY job and even 25mm made a huge difference to my flat. Have a dig around the Kingspan website for info.
    The problem with insulating on the inside is that you have nothing keeping the structural walls warm - they will be more prone to frost and thaw damage. Added to that, trying to form a complete insulating layer through partitions and floors will be very complicated.

    Quote Originally Posted by J0LL0 View Post
    Hi. When you say you have only single skin wall, do you mean 9" (1 brick length) solid walls as used in Victorian era construction, or do you mean 4" (1 brick width) thick?
    The walls are stone and approximately 12" - 16" thick (it varies) The main body of the house was built in about 1825 with a gable end extension in about 1860 of similar construction.

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    Wow! that's some heavy duty construction. The good thing about internal insulation (with a suitable vapour check to avoid interstitial condensation) is your house would warm up quicker 'because' you don't have to heat the walls up every time your heating comes on. The sheer mass of that kind of construction would takes kilowatts of heat to warm up, which you really want to avoid if you can. You could reduce frost damage to the stone by using weather proof coatings. If you can prevent the stone getting wet, then frost damage should be minimal, as it's the expansion of the water that causes the damage.

  13. #13

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    Quote Originally Posted by J0LL0 View Post
    Wow! that's some heavy duty construction. The good thing about internal insulation (with a suitable vapour check to avoid interstitial condensation) is your house would warm up quicker 'because' you don't have to heat the walls up every time your heating comes on. The sheer mass of that kind of construction would takes kilowatts of heat to warm up, which you really want to avoid if you can. You could reduce frost damage to the stone by using weather proof coatings. If you can prevent the stone getting wet, then frost damage should be minimal, as it's the expansion of the water that causes the damage.

    My worry is that the house has no damp proof membrane and has some signs of rising damp. This is kept in check partly by heating the walls and drying them out. I know this might be a bit of a cop out, but I think that, without a DPM, this is the way the house was supposed to work. When it was built there would have been 5 fireplaces working which would throw out a heck of a lot of heat into the building. Also, would the walls not work as a big night storage system, slowly leaking heat back into the house?

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    Many people these days are saying rising damp is a bit of a myth, and I am inclined to agree. Before the '60s it didn't exist, but suddenly it was everywhere, coincidentally arriving with a rush of damp proofing companies at the time. The conventional way to measure damp is with a moisture meter, however these are really only conductance meters, and will give a positive result with any good conductor. Cinder blocks for example, give positive results when dry because of high carbon content!

    You're in Somerset right? So would that make your house Bath stone or Ham Hill stone? Both of these are fairly good performers in the damp stakes, especially compared to soft red rubber bricks common to many Victorian era houses. What kind of signs are making you think you have damp?

    By the way I do speak from experience, and despite having the misfortune of being a compulsive DIYer, I do have an 'ology in building engineering.

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    What is the current external wall finish as it will affect the planning situation? The modern polymer/acrylic renders are very different in appearance to trad lime or sand/cement render. If you stick ordinary stuff on a mobile substrate it won't stay on long, no matter how much eml is used.

    Damp is a real bugger to pin down, often its caused by simple condensation. When the 5 fireplaces were working, there would have been a hell of a lot of air moving which would have mitigated the build up of moisture as well.

    As has been stated, the thermal lag of a stone building can be useful once it gets up to temperature, but you will need to stick a lot of energy into the building fabric to get it going and also in your case, a lot of it will be warming up the outside rather than re-radiating back inside...

    I wouldn't be too hasty ruling out the internal insulation route, Kingspan do a plasterboard composite panel and also do calcs for you to keep building control happy, floors and partitions are easy to deal with, even with a bit of quilt stuffed into voids, its not an exact science nor does it need to be provided some ventilation is allowed for - if it were me, I'd price up both options, I'd be interested to see what was most cost effective. I don't work for Kingspan btw, just specify their product a lot (and the builder sticks in Jablite or Celotex to save cash )



    A

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    I have had a interesting conversation with a builder who is working on my daughters house......he maintains that with the advent of double glazing/draught exclusion/central heating/blocking in fireplaces etc what happened was that there was little if any ventilation in these old houses...... and consequently 'Damp' made an entrance in the 60's/70's........he also remarked that during that time builders/occupiers didn't include ventilation in the equation........and maintains that an average adult exhales something like half a pint of moisture into the atmosphere whilst they are asleep.....and without ventilation this is absorbed into the plaster....hence 'damp' appears.....seems plausible.
    When my daughter had the inside walls re-plastered the old plaster came off and plasterboard with some sort insulation was installed.....this was then skimmed.....under the floors on the ground floor the builder installed a reflective insulated blanket above the joists but below the boards (pretty cheap stuff)......he also installed new and additional air bricks......and some sort of damp proof course which is silicon based and simply squeezed into the joint in the bricks and this permeates across the bricks causing a barrier (also cheap).....the outcome of this work was a considerable increase in the 'cosiness' in the downstairs reception rooms.......my daughters next project is to install a dual fuel (wood/coal/coke) fire in the front room, and use this instead of the expensive central heating.
    Another friend of mine has a dual fuel fire in his huge reception room.......I've been round there in the depths of winter and we had to open the windows because it was so hot.......I'm considering knocking a wall down between my kitchen and dining room (which will make a 30x14 room) and installing one.
    I'm quite interested in this topic as I and my wife are starting to make plans for our retirement......so without regular earned income I don't want to be spending my autumn years sitting in front of a single bar fire with a blanket around me......and I'm am not moving into a little square rabbit hutch until I can't walk or see and forget who I am
    Now all the gear but still no idea.

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    Quote Originally Posted by Woody123 View Post
    didn't include ventilation in the equation........and maintains that an average adult exhales something like half a pint of moisture into the atmosphere whilst they are asleep.....and without ventilation this is absorbed into the plaster....hence 'damp' appears.....seems plausible.
    Correct, add laundry, showers/baths and cooking and serious amounts of moisture will be floating about looking for cold surfaces...

    My flat is part of a building dating from 1876 and has 3 external walls. It had had plastic double glazing installed when we bought it but little ventilation and no insulation. The condensation was terrible and my cheapo humidity meter/weather station was showing over 80% if the washing was hanging... Obviously we had a problem with condensation and the resultant mould (especially behind furniture). Lined all the rooms with composite boards on battens (providing an air gap), new skirtings and architraves (no cornices in the flat) and we didn't notice losing a couple of inches of space although hanging heavy things from the walls is a bit of a bind... Heating bills dropped, condensation now not an issue but I run a dehumidifier when the laundry is hanging as ventilation is still poor (not got round to sorting that yet...), a load of washing will yield over a litre of water - 2 small kids = lots of washing...

    Current thinking is to reduce air losses from a building and to recirculate as much as possible through heat exchangers before exhausting it. My take is it is very difficult to make Victorian technology perform efficiently in this respect so compromises need to be made.

    A

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    Quote Originally Posted by Quercus View Post
    Found this little video on one site.
    That video looks really interesting and it looks like something a something a competent DIY'er could do.
    My House was built in 1926 and although the external walls are of 2 brick construction there is no cavity so this appears to be a product worth considering.
    Now all the gear but still no idea.

  19. #19

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    Sorting loss of heat is a good thing but without adequate ventilation, you're sure to get damp. The trick is maintaining an exchange of air, while minimising cold spots & direct draughts.
    May the gentleness of morning, greet your silent passage through endless waters...

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    Useful blog. It started me thinking about external insulation on my 1898 house. I must cut the cost of heating and I can't turn the thermostat down anymore, at least while she is watching, She doesn't approve of my answer for more woolies to keep warm. Women!!!!

    Things have changed in the last ten years.

    It's amazing what comes up on SotP!!!!

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  21. #21

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    Quote Originally Posted by J0LL0 View Post
    You're in Somerset right? So would that make your house Bath stone or Ham Hill stone? Both of these are fairly good performers in the damp stakes, especially compared to soft red rubber bricks common to many Victorian era houses. What kind of signs are making you think you have damp?
    Bath/Ham Hill stone? I wish. I live just down from an old (retired) quarry and believe the stone for the house has come from there. Geologist google tells me that the stone would be carboniferous limestone. The inidcations of damp I am seeing are areas of crumbling plaster at the lower parts of the walls (wall/skirting board interface).


    Quote Originally Posted by Davy 90 View Post
    What is the current external wall finish as it will affect the planning situation? The modern polymer/acrylic renders are very different in appearance to trad lime or sand/cement render. If you stick ordinary stuff on a mobile substrate it won't stay on long, no matter how much eml is used . .

    I wouldn't be too hasty ruling out the internal insulation route, Kingspan do a plasterboard composite panel and also do calcs for you to keep building control happy, floors and partitions are easy to deal with, even with a bit of quilt stuffed into voids, its not an exact science nor does it need to be provided some ventilation is allowed for - if it were me, I'd price up both options, I'd be interested to see what was most cost effective. I don't work for Kingspan btw, just specify their product a lot (and the builder sticks in Jablite or Celotex to save cash )
    Current finish is trad sand/cement render. At present, aside from a few cracks, it's in not too bad condition. I would intend to use fixings which would fix through the render into the stone wall behind.

    (careful what you say - I work for a concrete frame contractor and we use Celotex and Jablite regularly . . .).

    Quote Originally Posted by Woody123 View Post
    Another friend of mine has a dual fuel fire in his huge reception room.......I've been round there in the depths of winter and we had to open the windows because it was so hot........
    We do intend to install a double depth woodburner in the central chimney in the house (approx 11kW) which should help with both heating and air circulation.

    Ventilation is definitely a must (and the way the house is at present, not a problem). I'm still swayed toward external insulation as it seems there would be less upheaval and would be a simper installation than internal. I will have to check with the council to see if I require any sort of planing pemission when changing the render.

    All the discussion so far has been very helpful as it has made me clarify my thinking about what exactly is required.

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    11KW is absolutely huge......my mate has 7KW and my daughter was told that she only needed less than 5KW.......are you sure that you want that much?
    Now all the gear but still no idea.

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