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Housing - Renovation: Internal insulation on solid walls

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    • CommentAuthortony
    • CommentTimeMay 8th 2009
     
    50 mm ??? too thin!!!
    • CommentAuthorSaint
    • CommentTimeMay 8th 2009 edited
     
    NTP,

    The savings would be mid £20s i.e £25- 26/m2 down to maybe £16/m2 so its significant

    CommentAuthorwellburn CommentTime2 hours ago quote
    don't get blown away by aerogel, - it's less than twice as good as kingspaN / pir / pur
    ie - 10mm aerogel is only about the same as 18mm kingspan - which while being an improvement, - is no where near enough !!! - not for building regs, - not for anyone. - and it is WAY expensive. It really is about labour, - not cost of materials UNLESS you choose aorogel, - so just bite the bullet, - do the maths, - and buy big fat foam boards.

    Wellburn is of course mathematically correct. You save 8mm of space by using Aerogel against Kingspan but then then again equally you save 11mm of space by using Kingspan against super cheap old mineral wool and at what cost?
    Of course and again I agree we're not talking just 10mm Aerogel on a solid wall to meet Building Regs, more like 30mm or for Kingspan 54mm or mineral wool 88mm. Then do you need battens? Ultimately how much do you value internal space? In London and inner cities pretty much, in the shires maybe not so
    • CommentAuthorSaint
    • CommentTimeMay 8th 2009
     
    Tony, agree absolutely.
    50mm EPS externally is little better than what we achieve by full filling 1970s built cavities and that costs £400-£500. Admittedly not such a perfect solution but one that would seem to cost just 10% of the external option. Likewise internal insulation would probably be 50% of that cost.

    Isn't it time we got to grips on this forum with what the definition of thermal insulation is?
    Just because the brand name contains a prefix referencing an organic product, a prefix referencing a "state of the art technology", is made from recycled waste, is derived from animals or is credited with a performance not measurable by any internationally recognised norm should not detract from the fact that a thermal insulation should provide a reasonable, achievable and measurable resistance at a given thickness.
    Some so called thermal insulations mentioned herein have thermal performances no better than wood.
    Perhaps we should insist on a thermal resistance no lower than 1.25m2W/k for a 50mm thickness before we can call the product thermal insulation in the true sense. Any thoughts/comments?
    • CommentAuthortony
    • CommentTimeMay 8th 2009
     
    How come the standard thickness for external insulation on the continent is generally 200mm?

    I was doing 50 mm 30 years ago and am embarrassed about that but all the effort of doing external insulation and using so little insulation seems mad!
  5.  
    The law of diminishing returns (all figures in imperial units for ease of reading):

    If you have a solid double brick wall, its R value is about R2. If you add 50mm EPS, the R value increases to about R12. You have now reduced your heat loss by a factor of 6. So, say you were losing $1200 of heat through your walls per year, now you are losing only $200. If you increase the insulation from 50mm to 200mm, your R value is now R42 and so your heatloss is reduced by a factor of 21, so now you'd be losing $57 of heat through your walls per year. The 50mm of insulation saved you $1000 per year, the extra 150mm of insulation only saves $142.

    Now, it's true that labour costs dominate external insulation. Don't forget, though, that the improvements in air tightness will be the same with the 50mm of insulation as with the 200mm. I don't know how much extra material cost the 200mm of insulation would have over the 50mm, but the payback of that extra 150mm is much much longer than the first 50mm. And the lower your heating bills were in the first place, the worse the ROI on the incremental insulation is.

    Paul in Montreal.
    • CommentAuthorSaint
    • CommentTimeMay 8th 2009 edited
     
    Nick,
    Exactly and there's the rub. U value of a solid brick wall is accepted as 2.1W/m2K.
    Adding 50mm EPS takes it to 0.54 W/m2K, allowing for a bit of render then maybe 0.52W/m2K.

    Not quite the 6 times savings as quoted by Paul in Montreal but still substantial.
    Nowhere near building Regs of course which I know is where you're heading. To achieve that you'd need 85-90mm EPS

    ** Leepike, our postings crossed over. How do you get 0.37W/m2K with 50mm EPS???
    • CommentAuthorleepike
    • CommentTimeMay 8th 2009
     
    building regulations are quoting 65mm as more than needed, although 50mm wall insulation is still within the limits
    • CommentAuthorleepike
    • CommentTimeMay 8th 2009
     
    all my U value calculations are done by an independent INCA representetive
    • CommentAuthorSaint
    • CommentTimeMay 8th 2009
     
    Lee there's something wrong with that U value calc. Could be for a cavity wall? Impossible on normal 9" solid brickwork
    • CommentAuthormike7
    • CommentTimeMay 8th 2009 edited
     
    A calculator which I find I am not able to post gives resistances thus:-

    9in solid brick .36, 12mm plaster .08, surfaces int and ext .18, total .62 or u-value 1.62
    As above .62 plus 50mmEPS 1.35 and 12mm render .02, total 1.99 or u-value .50
    As above but plus 100mm EPS 2.70 and 12mm render, total 3.34 or u-value .30

    Hope this helps
    • CommentAuthorleepike
    • CommentTimeMay 8th 2009
     
    cheers MIKE7, very much appreciated
    • CommentAuthorSaint
    • CommentTimeMay 8th 2009
     
    Thanks Mike7, we're just about in agreement.

    If you use the BRE U value calculator you'll get:

    Solid brickwork thermal conductivity 0.77W/mK so at say 225mm thick an R value of 0.292 m2k/W
    An internal resistance (Rsi) 0.130 m2k/W
    An external resistance (Rse) 0.04 m2k/W

    Adding all the R values gives you 0.462m2k/W This converts then to a U value of 2.16 W/m2K
    The BRE, EST and Ofgem all use this figure rounded down to 2.1W/mK as the baseline value for a 9" solid brick wall

    So unless Lee's EPS has a thermal conductivity approaching 0.02W/mK (like phenolic) its impossible for 50mm EPS to achieve a 0.35W/m2K U value
  13.  
    I have a SAP calc for a 225mm masonry wall with 40 phenolic foam showing 0.45.
    • CommentAuthorSaint
    • CommentTimeMay 8th 2009
     
    Thanks Nick,

    Exactly. The same wall with 50mm phenolic would give you 0.35W/m2K (taking phenolic at 0.021 W/mK)
    • CommentAuthormike7
    • CommentTimeMay 8th 2009
     
    I see the figure I took for the brick conductivity was for an inner wall (.62). I should have used their figure for ext. wall (.84), which would give results matching more closely Saint's figures.
    • CommentAuthorNTP
    • CommentTimeMay 8th 2009 edited
     
    Posted By: SaintNTP,

    The savings would be mid £20s i.e £25- 26/m2 down to maybe £16/m2 so its significant

    CommentAuthorwellburn CommentTime2 hours ago quote
    don't get blown away by aerogel, - it's less than twice as good as kingspaN / pir / pur
    ie - 10mm aerogel is only about the same as 18mm kingspan - which while being an improvement, - is no where near enough !!! - not for building regs, - not for anyone. - and it is WAY expensive. It really is about labour, - not cost of materials UNLESS you choose aorogel, - so just bite the bullet, - do the maths, - and buy big fat foam boards.

    Wellburn is of course mathematically correct. You save 8mm of space by using Aerogel against Kingspan but then then again equally you save 11mm of space by using Kingspan against super cheap old mineral wool and at what cost?
    Of course and again I agree we're not talking just 10mm Aerogel on a solid wall to meet Building Regs, more like 30mm or for Kingspan 54mm or mineral wool 88mm. Then do you need battens? Ultimately how much do you value internal space? In London and inner cities pretty much, in the shires maybe not so


    Thanks Saint,

    I have misunderstood you. As mentioned quite rightly, space is important for me and that being due to not fiddling with the window frames. 20 mm aerogel will fit my window frames (30mm off the wall) nicely and to be honest the price wouldn't be a problem since I have only got a few external walls and most of them have big sash windows.


    What do you think is the better/easier option: fermacell or plasterboard ?
    • CommentAuthorNTP
    • CommentTimeMay 8th 2009 edited
     
    Leepike,

    I have got a leasehold and the flat downstairs is still owned by the council so I'd rather do the internal insulation. Thank for the post anyway.
    • CommentAuthorModerator
    • CommentTimeMay 8th 2009
     
    Users need to be reminded that if you want to offer quotes or prices for your services or products to other users then please do it using the whisper facility directly to them otherwise it may be viewed as advertising and get deleted.
  19.  
    Leepike , your ballpark figure looks pretty fair.
    Its nice to see some people giving sensible quotes for external insulation ,its similar to what I'd charge
    I'm a trademen myself and done some eps,xps/external render work in the past
    as you where advertising yourself , I was interested to see what you called ' not expensive'
    As I mentioned I think external insulation needs keener pricing to get a better uptake , otherwise
    it will just be to expensive for the average Jo to consider.
    I'm a bit confused about the 50mm EPS on solid walls though , I thought current UK regs where looking for U =0.3
    on walls , which 100mm EPS approximately achieves.
    I understand why its easier to sell 50mm at a fair price , its not the extra insulation cost , which is surely only several £ per m2 , but the issue of dealing with detailing such as verges, soffit, pipework ,50mm will usely
    slot in without to much greath, anymore and you've got some large additonal costs
    Really though I think we should be looking toward U=0.25 as a minium and better where possible
    I believe in Germany they got a massive program to upgrade the housing stock and 200mm EPS is quite common
    surely we should be following there lead
    what insulation/render system do you use , if you dont mind me asking.

    cheers Jim
  20.  
    Jim, for refurb it's 0.35, but I agree we ought to be going for better.
    • CommentAuthorSaint
    • CommentTimeMay 9th 2009
     
    NTP,

    Apparently the Fermacell laminate is outselling the plasterboard and by some. I'd have thought the other way but what do I know?
    Reasons are given as durability and the fact that cabinets can be fixed to it. Here's a link for the Fermacell
    http://www.xella.co.uk/downloads/gbr/broschures/HandyGuide_s1104.pdf
    • CommentAuthorNTP
    • CommentTimeMay 19th 2009
     
    Hello again,

    I have read some material about cavity wall insulation and was wondering if it would apply to my Victorian flat. I only own the top floor flat so if I were to use cavity wall insulation could it be restricted only for the one of the 2 flats in the house? In other words is there a cut off level between the 2 flats in relation of this space between the bricks? I would have thought that if I were to go for it I might need to get my neighbour to join me.

    Any ideas guys?
  23.  
    Does your Victorian flat have a cavity wall? most are solid wall

    If so really you need to get your neighbour involved , the wont be any cut off point like you suggest, tell them they'll get there money back in 2 years (ish)
    in fuel bill savings ,
    • CommentAuthorNTP
    • CommentTimeMay 19th 2009
     
    Thanks fro your advice Jamesingram,

    Involving the neigbour means not doing it because they are renting the place from the council.
  25.  
    If there on benefits they may be able to get it for free ,

    Councils need to get off there arses and start improving the housing stock for those
    most affected by fuel poverty by organising this as the freeholder/landlords

    http://www.government-grants.co.uk/cavity-wall-insulation-grants.shtml
    http://www.freeinsulation.co.uk/?gclid=CMuyi-efyZoCFRUhnAod3Fz22g

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