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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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    • CommentAuthornstansbury
    • CommentTimeJan 13th 2019 edited
     
    Hi all,

    We're converting our integrated garage into a habitable space with a well insulated, airtight timber frame in place of the garage door. The final detail I haven't resolved fully is the timber frame junction with the existing masonry.

    The timber sole plate will be sitting on Marmox Thermoblocks to avoid thermal bridging with the existing concrete slab at that junction. However, the frame uprights fix into external double skin brick walls, and the frame header attaches to a full width, externally exposed concrete lintel.

    Whilst internally the masonry will be well insulated, I am trying to figure out how to make the timber frame/masonry junctions both airtight and create a thermal break.

    The timber frame will be taped around the masonry junctions internally with the VCL, but I am concerned that the timber frame face onto the masonry will not be airtight at all allowing air around the insulated frame in front of the VCL as well as cold bridging with the masonry.

    I've read somewhere about EDPM tape that you can attach to timber stud faces on masonry, but can seem to find anything online.

    What would be the recommended build up to avoid thermal bridging and seal the timber studs along the masonry junctions?

    Cheers,

    Neil
    •  
      CommentAuthordjh
    • CommentTimeJan 13th 2019
     
    Stand the timber studs away from the masonry, maybe with small blocks to secure horizontally as required. Fill the gap with insulation, either flexible like mineral wool batts, or pre-cut rigid blocks installed before the studs.

    Airtightness either or both of gluing rigid insulation to the wall and to whatever is the airtightness barrier in your stud wall construction or glue the airtigtness membrane to the wall using appropriate products (primer & Orcon F etc or tapes designed for the purpose). Make sure the membrane and tapes are not tight. There should be excess material to allow for subsequent movement.

    Gaskets are another possible way to seal timber to masonry. See http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15167 and https://www.aecb.net/forums/topic/airtightness-timber-frame-sole-plate-solution/

    If you can, cover the outside face of the stud wall and the concrete lintel with some EWI.
    •  
      CommentAuthorfostertom
    • CommentTimeJan 14th 2019
     
    Why not a fat wodge of mastic between stud and masonry? Can anything else really follow the irregular contours of masonry, even modern brickwork?
    Squirty foam doesn't claim to be at all airtight even if it fully fills a gap.
  1.  
    ''Squirty foam doesn't claim to be at all airtight even if it fully fills a gap.''

    Illbruck do one which does.

    What about something like Compriband/Isobloco expanding foam tape?
    •  
      CommentAuthordjh
    • CommentTimeJan 14th 2019 edited
     
    Posted By: Nick ParsonsIllbruck do one which does.

    As do Soudal, Everbuild ...
    • CommentAuthorgoodevans
    • CommentTimeJan 15th 2019
     
    One in particular I've noticed is Soudal Sudafoam SWS flexifoam. It looks like it retains expandability and compressibility post curing - so if the crack expands or shinks the foam should follow it if it remains adhered to the surfaces.
    •  
      CommentAuthorfostertom
    • CommentTimeJan 15th 2019
     
    Well that means a rethink then
    • CommentAuthorDarylP
    • CommentTimeJan 15th 2019
     
    Soudal Fexifoam is good. works well, cheaper than Ilbruck in boxes x 12 cans IIRC.
    • CommentAuthornstansbury
    • CommentTimeMar 11th 2019
     
    Thanks all, decided I would go with this membrane https://obexuk.com/product/cortex-1500-epdm-membrane

    This should be easy to fix between the timber frame and the masonry and then foam fill any gaps after it
    •  
      CommentAuthordjh
    • CommentTimeMar 11th 2019
     
    What is your airtightness barrier for the stud wall and for the masonry wall? Why/how are the studs part of your airtightness barrier?
    • CommentAuthornstansbury
    • CommentTimeMar 11th 2019
     
    It's a taped poly VCL. This is to act as a thermal break between the masonry and timber studs and stop air leaking between the masonry/timber junction and behind the VCL
    •  
      CommentAuthordjh
    • CommentTimeMar 11th 2019
     
    You don't need a thermal break, air is quite a good thermal break. Simply don't put the stud next to the masonry.

    I don't understand your concern about air leaking between the masonry/timber junction if it is covered by a poly VCL. Perhaps a diagram would help me understand.
    • CommentAuthornstansbury
    • CommentTimeMar 11th 2019
     
    The structural design is that the headers are fixed directly to the masonry and concrete lintel, so stand-offs are not an option sadly.

    The VCL will run over the timber frame internally and be taped over the timber/masonry junction - effectively sealing the VCL to the masonry, but not actually sealing the studwork itself. To me that reads that air could pass between the timber and masonry and filter in behind the VCL?
    •  
      CommentAuthordjh
    • CommentTimeMar 12th 2019
     
    Sorry, I'm not sure what you mean by headers?

    Again, I don't understand why the studwork needs to be sealed. It's behind the VCL, so it's of absolutely no consequence. What about the air on the opposite side of the stud? Surely that is free to 'filter in' in huge volumes?
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