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Housing - New Build: What Block spec with External wall Insulation?

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    Has anyone used 140/150mm blockwork (in conjunction with a smart engineer) with external wall insulation say neopor EPS to get a passive house wall construction of minimal thickness? If so what block did you use. I don't like aircrete type blocks especially as i am looking to plaster the inside for airtightness. What is the best lambada value for a block that receives wet plaster well without cracking? Its a balance! your views would be welcome.
    • CommentAuthortony
    • CommentTimeOct 27th 2012
     
    I hate aircrete, how about recycled aggregate blocks?
    • CommentAuthorjamesingram
    • CommentTimeOct 27th 2012 edited
     
    I used 150mm fibolite (they have a good key for wet plaster , and are in my mind , half way between AAC and conc. blocks in terms of weight, density and strength ) , 200mm graphite eps , ( U=0.15 approx ?)
    though medium dense recycled agg. would be better due to the recycled element and denser so better thermal mass ?
  4.  
    jamesingram - How many stories did you build? Did you have to do anything special in order to use 150mm blocks instead of 200mm ones?
  5.  
    Thanks didn't realise Plasmoor do an expanded clay aggregate block.
    Just been reading about the ravenscroft wimbish passive house scheme in Essex where they did use aircrete.
    http://www.wimbishpassivhaus.com
    Not much detail on the 2 coat plaster system used although they do appear to have used expanded metal mesh in places.
    If done in dry conditions with suitable plaster and mesh around windows etc maybe aircrete could be ok? Dare i risk it for my own house!
    • CommentAuthortony
    • CommentTimeOct 28th 2012
     
    nope, it moves about too easily and cracks too with resultant problems like aesthetics, air tightness, repair costs etc
  7.  
    Not really a full answer why does it move and crack using thin bed mortar? Bramhall construction who built it for Hastoe housing association are part of a very large group. Doubt they would do something that would result in cracks loss of airtighness etc. They have done a lot of monitoring of it post completion. I will find out !
  8.  
    phfan , only single storey extensions so far with that method. No nothing special was done.
    Could you say first floor joist tide wall at 2.4m so second storey could be 150mm also ?
    I know on other discussion here, people have had trouble doing that ( getting it passed/design/calcs etc. for B regs )
  9.  
    Neil , interesting link , lots of construction details to look at .
    • CommentAuthorseascape
    • CommentTimeOct 28th 2012
     
    Tarmac Homes did a couple of homes at University Nottingham - they used 215mm Top Block Toplite aircrete. They were on the Zero Carbon Hub website, which I presume still exists.

    On the web it says they used 150mm EPS - but when I spoke to them they said it was Kingspan - not sure who to believe. There maybe other builds on that site that used 150 blocks.
  11.  
    Hi Neil,
    I've built to Passive House standard with externally insulated 150mm Aircrete, with ext ins 100mm concrete block for an extension, with ext ins Poroton and with ext ins 210 cavity block and solid block.
    The biggest problem with block construction is that the airtightness is done to late to do anything about it, that's why we've developed an airtight concrete block with an Irish block manufacturer.
    The Aircrete blocks didn't crack for me but they did for a friend of mine.
  12.  
    Posted By: neilgorswiftHas anyone used 140/150mm blockwork (in conjunction with a smart engineer) with external wall insulation say neopor EPS to get a passive house wall construction of minimal thickness? If so what block did you use. I don't like aircrete type blocks especially as i am looking to plaster the inside for airtightness. What is the best lambada value for a block that receives wet plaster well without cracking? Its a balance! your views would be welcome.


    If you are putting EPS on the outside and looking for airtightness as well as a 140/150mm masonry core on a new build then have you looked at using ICF instead? Less likely to have airtightness problems if done right.... some systems go down to 100mm masonry core giving you bit more room for insulation, poured wall stronger than blockwork wall for any given thickness.
  13.  
    Willie
    I have - both durisol and trad icf
    I some how think block with EWI and thermal mass on the inside will be the cheapest?
  14.  
    Posted By: neilgorswiftWillie
    I have - both durisol and trad icf
    I some how think block with EWI and thermal mass on the inside will be the cheapest?


    Worth double checking that - plain old blockwork may well work out cheaper, but if you need to add anything like wind posts, thin bed jointing, fancy blocks and so on then maybe not.
    • CommentAuthorjamesingram
    • CommentTimeOct 30th 2012 edited
     
    i'd estimate, thin coat render/200mm eps/150 block is approx same cost as block/100mm cavity fill/block to standard regs.
    footing can be 450mm wide rather than 600mm .
    • CommentAuthortony
    • CommentTimeOct 30th 2012
     
    which is better though?
    • CommentAuthortony
    • CommentTimeOct 30th 2012
     
    Think about air infiltration, thermal bypass, problems with air tightness, best insulation scenario etc
  18.  
    My view would be you're getting more for your money with EWI/solid block in all the areas you mention.
    Though I do have concern regarding longevity of thin coat EWI relative to the trad. brick or dash render block external finish and how this might effect the energy input/output over life span of building , if it required renewing say after 25 years
    •  
      CommentAuthorjoe90
    • CommentTimeOct 30th 2012
     
    Posted By: jamesingramMy view would be you're getting more for your money with EWI/solid block in all the areas you mention.
    Though I do have concern regarding longevity of thin coat EWI relative to the trad. brick or dash render block external finish and how this might effect the energy input/output over life span of building , if it required renewing say after 25 years


    This is where I think Tony got it right with his house, block inner, thick insulation and a brick facade. Solid, well insulated and external face should need no maintenance and be as hard as, well "bricks"

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