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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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    • CommentAuthorbogal2
    • CommentTimeJan 23rd 2024 edited
     
    Im really sad to hear this forum may be closing as its been a big help to me. Hi, just wanted to run this plan for insulating a suspended wooden floor with a good ventilated crawl space below in a victorian house. Ive had a good read of all the posts on here and still feel a bit unsure

    The plan I have is to:
    Lift boards
    fix 35mm woodfibre boards to underside of joists.
    Fix and seal breathable windtightnesss membrane below.
    Fill 180mm space between joists with steico zell loose fill wood fibre.
    Airtightness membrane on top sealed to perimeter of room with tape.
    Replace boards.

    Grateful for any feedback.
    •  
      CommentAuthordjh
    • CommentTimeJan 23rd 2024
     
    Posted By: bogal2fix wood to bottom of joists.
    I'm not clear what you intend here. What is the product? Are these fixed from above or below? Do they provide continuous cover underneath the joists, and if so what is the windtightness membrane for? If not, what do they do?
    • CommentAuthorbogal2
    • CommentTimeJan 23rd 2024
     
    I was going to use steico universal wet fixed from below to reduce thermal bridging and hold the loose fill insulation in. Maybe the wind tightness membrane is a bit over the top!
  1.  
    Posted By: bogal2fix wood 35mm fibre boards to bottom of joists.

    I presume are there so that the steico zell loose fill wood fibre can be poured in as a full fill. But I also don't see the need for a wind tightness membrane if the boards cover the underside of the joists.

    I woud use a VCL membrane instead of the top air tightness membrane - to perform both functions.

    Edit to say cross posted with bogal2
    • CommentAuthorGreenPaddy
    • CommentTimeJan 23rd 2024
     
    What do the mice think about the wood fibre boards and the loose fill. Are they in favour of it?
    • CommentAuthorbogal2
    • CommentTimeJan 23rd 2024
     
    I should imagine they would love it as with most other insulation materials or membranes! My wetsuit got eaten in the shed a few years ago, so I don’t think they’re on an organic diet!
    •  
      CommentAuthordjh
    • CommentTimeJan 23rd 2024
     
    Posted By: bogal2My wetsuit got eaten in the shed a few years ago
    Perhaps they were just breaking it up to use as nesting material?
    • CommentAuthortony
    • CommentTimeJan 23rd 2024
     
    I would prefer to see a vb/air tightness barrier in the warm side of the insulation
    • CommentAuthorbogal2
    • CommentTimeJan 24th 2024
     
    I was planning on proclima intello for the vb/air tightness under the floorboards.
  2.  
    Can I add a bit? Additions are *between asterisks*

    Lift boards
    *Check masonry and joist ends for moisture*
    *If concerned re results (a) investigate source and remedy as necessary/possible*
    *If joist ends <20% moisture content but any residual concern re moisture to walls themselves (external and internal) consider using XPS or similar so that wood-fibre cannot 'suck'.*
    fix 35mm woodfibre boards to underside of joists.
    Fix and seal breathable windtightnesss membrane below.
    Fill 180mm space between joists with steico zell loose fill wood fibre.
    Airtightness membrane on top sealed to perimeter of room with tape.
    Replace boards.

    I like the use of Intello and I suspect that the wind-tight membrane below the 'rigid WF is not necessarily required. However if doing without it I would prime and seal the joints in the WF layer. You want to seal perimeters too, of course, which brings me back to the point re any moisture in the sub-floor walls, since the WF will 'suck'. Again, unless you find the walls absolutely dry as a bone I might come back to my XPS idea (tightly sealed) and then seal the WF to that.
    • CommentAuthorbogal2
    • CommentTimeJan 27th 2024
     
    Thanks Nick. Just been looking at how Es Tresidder did his Highland passivhaus retrofit suspended floors.It seems really good to me. Can be done from above, cheap eco friendly materials. Less risk than wood fibre exposed to damp.
    • CommentAuthorbogal2
    • CommentTimeJan 27th 2024
     
    Thanks Nick. Just been looking at how Es Tresidder did his Highland passivhaus retrofit suspended floors.It seems really good to me. Can be done from above, cheap eco friendly materials. Less risk than wood fibre exposed to damp.
      suspendedfloorshrink.jpg
    • CommentAuthorjms452
    • CommentTimeJan 27th 2024
     
    Have you thought of this system to avoid the need to lift the boards?:
    https://q-bot.co/
    • CommentAuthorbogal2
    • CommentTimeJan 27th 2024
     
    The ground below
    is very uneven and would prefer not to use foam. Looks very useful though!
  3.  
    It's a matter of opinion, but my understanding is that the cold soil below a Victorian suspended floor is supposed to act like a dehumidifier for the room above. Moisture vapour from the room, diffuses into the underfloor and either is removed by the through flow of air, or condenses in the cold soil and drains away. So when insulating my suspended floors, I have tried to keep them breathable without a vapour barrier. I see other people using vapour barriers to keep the moisture within the room, in which case the room ventilation needs to be up to scratch or there will be condensation on wherever the next-coldest surface is.

    It's like an upside down version of a loft space. Some folks like to fit their insulated ceiling with a vapour barrier, others like to use breathable loft insulation and keep the loft well ventilated.

    Either way, the airtightness is important, particularly round the skirting boards, improving this made a big difference to our floors.
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