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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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    • CommentAuthormichaeld
    • CommentTimeSep 9th 2018
    Hello all,
    I'm in need of a bit of advice regarding condensation issues we have in our home during the colder months of the year. After knocking a few blocks out of the wall I discovered that we have solid foundations extending up about 450mm above ground level outside, which is also internal floor level. (I've included a wee diagram to explain) I had come to the conclusion that EWI was the answer thinking that the exposed solid foundation might be acting as a massive thermal bridge and causing the inner wall of the cavity to cool enough for condensation to occur. (Does this sound plausible?)

    I'm not 100% though so any thoughts?
    I had been told it could be the old dodgy pebble dash render letting moisture in and across the dpc, but we've had some pretty heavy rain this summer and there's been no sign of wet walls.

    Also, can I use EPS down to ground level? or would I have to use XPS? only it's nigh on impossible to get xps in Northern Ireland and delivery charges from the main land are crazy.

    Anyway, any help would be a massive help,
    Many thanks in advance,
    • CommentTimeSep 9th 2018
    You don't say where the condensation is occurring? Also, how old is the building?

    You show a DPC across the base of the wall, but is there also a DPM/DPC under the floor?

    As shown, yes the floor and the solid block wall are a big thermal bridge that will cool the inner wall.

    And yes, you can use EPS all the way down the wall and underground as well if required.
    • CommentAuthormichaeld
    • CommentTimeSep 9th 2018
    Thanks for replying djh,
    The condensation occurs about a foot or so above floor level and I'd say the house was built around the 60s? maybe? There's no sign of dpc under the timber suspended floor in my son's room.
    That's good to know about the eps,
    Many thanks
    • CommentTimeSep 9th 2018
    Ah, suspended floor, I hadn't thought about that :shamed: So presumably there are vents running through the solid blockwork and the floor is cold as well? That complicates things.

    EWI up from the ground or below running up even a metre or so would probably fix the condensation on the walls and could be made to look like a plinth. Obviously insulating the entire wall would be better still, but more work and expense.

    But you also need to think about how to insulate the floor - is there anything there at present?

    The other thing to think about is ventilation inside the house. Even a small amount of continuous ventilation can help to prevent condensation by lowering the humidity and stirring the air.
    ''EWI up from the ground or below running up even a metre or so would probably fix the condensation on the walls and could be made to look like a plinth.''

    Same principle, but a full floor height (and a bit):
      DSCF5848 - Copy.JPG
    • CommentTimeSep 9th 2018
    Good to know I'm not completely mad :bigsmile:
    Or that I am....!

    For a bit of context, I had done IWI for the client about 10 years ago on the 1st and 2nd floors. The ground floor would have been a lot more difficult to do internally, so we chose to run the EWI about 600mm above the level of the IWI to cloak the thermal bridge and, because I hate 'industry standard' cappings (or, more to the point, the mastic - with a 30+ year life, of course.... - that they are 'gunged' in), we did a bevelled top and lead flashing.
    • CommentAuthorbxman
    • CommentTimeSep 9th 2018
    Hi Michael
    You say the cavity is filled

    Do you know what the cavity in the wall is filled with?
    and just as important
    Are there any or were there ever any vents into this cavity that have been closed off ?
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