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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.

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    I've had my floor up, ready to insulate, and I noticed the subfloor in the corner by the door was damp. On closer inspection outside, there's no fall on the pavement gutter, which takes the water from my downspout to the road, so water had been running back into the building through a hole in the pavement.

    I've now filled the hole, so hopefully that's that sorted, but I was about to start putting down insulation. Is it worth waiting for it to dry out a bit, or will it find an equilibrium anyway?

    Many thanks
    • CommentAuthortony
    • CommentTimeDec 10th 2017
    What is your floorbuild up, wood or concrete or floating floor, where will the dpm/vb be located?
    Hi Tony,

    Build up will be-
    pea gravel, eps, dpm, eps, chipboard, floorboards.
    • CommentAuthortony
    • CommentTimeDec 10th 2017
    Ok to do it straight away, I would put the dpm on top of the eps
    • CommentTimeDec 10th 2017
    Putting the DPM in the middle protects it against nails etc.
    • CommentAuthortony
    • CommentTimeDec 10th 2017
    Depending on the thicknesses of the eps there is a risk of condensation on top of the dpm, only thin eps on top of dpm say 25mm then
    Thanks for the comments.

    Currently going for 100mm below dpm and 75mm above.

    Don't quite understand how the thickness of the eps will affect condensation?

    • CommentAuthorRick_M
    • CommentTimeDec 11th 2017
    My understanding is condensation is more likely if the dpm is cold and if moving interior air can reach it, if the dpm is under a lot of EPS it's more likely to be cold. Is it possible to make the chipboard an airtight layer (and join it to the air barrier in the wall)?
    Hang on - where's the VCL? Are you looking to the DPM to do double-duty?
    I can see the importance of the VB when the DPM is beneath a concrete slab, but is it necessary if all that's between the dpm and vb is some eps?

    Not against putting in a vb but thought I might manage without?

    Thanks for the comment rick, it would be possible to airtight the chipboard I think. Might be the easiest solution.
    Normal insulation procedure is for VCL to be on the warm side of the insulation. What you seem to describe is to use the DPM as a VCL *on the cold side*.

    Is chipboard recognised as airtight?
    • CommentAuthortony
    • CommentTimeDec 11th 2017
    Airtight is irrelevant, we are talking about vapour and that will pass straight through chipboard.
    ''Airtight is irrelevant, we are talking about vapour and that will pass straight through chipboard.''

    I agree we're talking about vapour.

    I was referring to Rick_M's comment (re using chipboard as an a/t layer) above.
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