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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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorandyman99
    • CommentTimeSep 12th 2018
     
    We are having a re-think on our extension construction. What would be the best build up for a single skin wall, with EWI. We already have dwarf walls from foundations to DPC that are 220mm wide? Thanks.
    • CommentAuthorgyrogear
    • CommentTimeSep 12th 2018
     
    How about SIP's, no need for EWI then...

    https://en.wikipedia.org/wiki/Structural_insulated_panel#Benefits_and_drawbacks

    gg
    • CommentAuthortony
    • CommentTimeSep 12th 2018
     
    140 solid concrete blocks, 200 eps, mesh and hightech render , inside simply wet plasrered
    •  
      CommentAuthorfostertom
    • CommentTimeSep 12th 2018
     
    140 won't pass Bldg Regs automatically - 190 is 'deemed to satisfy' (which means 215 in available size). Cd be worth getting a Structural Engineer to calc the structurally necessary thickness - can vary in different parts of the walls.

    Why not stud?
    • CommentAuthorandyman99
    • CommentTimeSep 13th 2018
     
    SIP's first, we did consider, but in practice this is a relatively small extension and nobody was interested. The overheads of transport/cranes seem to make a small project unviable (our experience).

    Next was (is) TF but we are having issues with supplier over what is/isn't included and are turning cold on them. Obviously I dont want to go into this publicly.

    The good news is we have brilliant builders and our structural engineer is happy for a single skin block build on our 220mm walls at DPC. So my aim is to understand the best way forward, best types and size of blocks to use and anything else allowing me to talk constructively with engineer and builder.

    Thanks all.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 13th 2018
     
    OK, not factory-made TF, but why not on site studwork? Multiple advantages esp if single storey, admittedly not so much if multi storey, but still worth checking seriously. I'll gladly give my succesful recipe if interested.
    • CommentAuthorgyrogear
    • CommentTimeSep 13th 2018
     
    or why not HEMP...

    https://www.youtube.com/watch?v=sVlYDWr31fQ

    gg
    • CommentAuthorandyman99
    • CommentTimeSep 14th 2018 edited
     
    FT yes definitely interested, we are considering all options at the moment.
    • CommentAuthorgoodevans
    • CommentTime4 days ago
     
    I was able to get an engineer to sign off on 140mm block single skin - he just needed to check the various failure modes of the wall - provided the wall has returns/buttress walls every 5m or so no wind posts are required.
    • CommentAuthorandyman99
    • CommentTime3 days ago
     
    Our structural engineer has recommended Thermalite Turbo blocks (215mm). He has also recommended both internal and external insulation which seems an unnecessary expense, so we would almost certainly just go for EWI. If we do go for thickish EWI, would it be better to go for a more standard (assume cheaper) block?
    • CommentAuthorgoodevans
    • CommentTime3 days ago edited
     
    Yes - I would go for EWI only. There is no need to have two layers of insulation. If the house is occupied most of the time there is little benefit in insulating inside.

    Thermally a 215 thermolite block and 165mm grey EPS is equivalent to a 140mm lightweight aggregate block (850kg/m2) and 200mm of grey EPS. This extra 40mm affects usable floor area and how much light comes in the windows. For my rectangular house 40mm reduces the 100m2 floor area by 1.6 m2.

    I had to keep the weight of the walls down to keep the foundation/pile loads manageable - if not I may have gone for heavier blocks given a choice - but the builders would not have been happy, at 12.5kg per block for 140mm lightweight aggregate blocks it's already getting hard work - for the cheaper denser blocks you would want to keep below 20Kg / block for the limit on single person handing - this would indicate 140mm blocks.

    Reports are that thermolite blocks will shrink (crack) more that aggregate blocks after the build due to their increased moisture adsorbing capacity and are more difficult to fix things to (windows/doors cupboards etc). Have a google around and see if the advantages of thermolite to you outweigh the disadvatages for your build.
    • CommentAuthorMike1
    • CommentTime3 days ago
     
    Aerated concrete block walls also have a tendency to crack, so be sure to look at the requirements for movement joints and bed reinforcement.
  1.  
    I've done a few small extensions using 140mm+200mm eps without engineer , BC happy after discussion and showing them the AECB Silver standard section drawings of similar.
    most dont like ultralite weight blocks now due to cracking and poor key for plaster.
    I use fibolite usually as they are easier(lighter) to work with and a mid way between thermolite type ACC and fenlite or other medium dense blocks and have excellent key
    • CommentAuthorgoodevans
    • CommentTime2 days ago
     
    For my build I used Interfuse Interlyte-Ultra blocks. These look similar the fibolite blocks that James mentioned. A good compromise between the aerated concrete blocks and the denser medium or dense concrete blocks.
    • CommentAuthorSilky
    • CommentTime20 hours ago
     
    Could look into a deep Poroton style block with thin joint mortar or adhesive + render, simplest solution in terms of trades
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