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Reducing thermal looping while preserving semi cavity

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  • 06-06-2020 2:40pm
    #1
    Yellow_Fern
    Registered Users Posts: 2,576 ✭✭✭


    I have a situation with a semi cavity wall with 110 mm Quinntherm of a completed house. I am doing some work on the reveals and now that the blockwork is exposed and it allowed me to realise that there is a cavity between the inner leaf and Quinn boards, ranging from 2mm to 10mm. It seems like there is thermal looping in action, even in the mild June weather. Given that some of the blockwork is exposed, would it be appropriate to try to fill this cavity with foam beads and diluted PVA to reduce the gap? This would hopefully preserve the cavity on the outer leaf face, so the wall doesn't become full fill.


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    #2
    chooseusername
    Registered Users Posts: 3,600 ✭✭✭chooseusername


    If the cavity is wider than the insulation, the insulation should be held against the inner leaf by the plastic wheels clipped onto the wall ties as the wall was being built.I can't see how you can pump the cavity now.


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    #3
    Yellow_Fern
    Registered Users Posts: 2,576 ✭✭✭Yellow_Fern


    Maybe this shows it better.

    The idea was to just pour the beads myself, not hire a company to pump them in.


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    #4
    sydthebeat
    Subscribers Posts: 41,037 ✭✭✭✭sydthebeat


    Beads aren't certified to be pumped into a cavity less than 40mm


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    #5
    Lumen
    Registered Users Posts: 31,013 ✭✭✭✭Lumen


    Closed cell foam is supposed to push existing insulation tight against inner leaf, but whether it's certified or not is a trickier question.


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    #6
    Yellow_Fern
    Registered Users Posts: 2,576 ✭✭✭Yellow_Fern


    Thanks for the advice. I guess the big risk is that moisture is trapped there. I was hoping to learn if there are other risks.


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    #7
    Yellow_Fern
    Registered Users Posts: 2,576 ✭✭✭Yellow_Fern


    It seems 2 mm expanded glass beads are available pretty cheaply. Might be a good solution for this problem.


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    #8
    Calahonda52
    Registered Users Posts: 12,194 ✭✭✭✭Calahonda52


    Lumen wrote: »
    Closed cell foam is supposed to push existing insulation tight against inner leaf, but whether it's certified or not is a trickier question.

    I don't know whether it would have the PSI to flatten boards that have been distorted in a cavity for a long time, if it did I would worry about the wall!

    I cant see any workable solution getting in behind the boards as you don't have full access so it might just exacerbate the looping

    “I can’t pay my staff or mortgage with instagram likes”.



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    #9
    Lumen
    Registered Users Posts: 31,013 ✭✭✭✭Lumen


    Calahonda52 wrote: »
    I don't know whether it would have the PSI to flatten boards that have been distorted in a cavity for a long time, if it did I would worry about the wall!

    Given the stories of Walltite cracking internal plaster I'd say it probably does!

    As ever though, there's the risk of creating impermeable pockets of moisture around the wall ties. IIRC, Walltite is certified in the UK for holding together walls with corroded wall ties, in which case you don't have much to lose. Putting it into a perfectly good cavity (well, structurally at least) is...brave.

    Are modern wall ties made of stainless steel or what?


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    #10
    Yellow_Fern
    Registered Users Posts: 2,576 ✭✭✭Yellow_Fern


    Calahonda52 wrote: »
    I don't know whether it would have the PSI to flatten boards that have been distorted in a cavity for a long time, if it did I would worry about the wall!

    I cant see any workable solution getting in behind the boards as you don't have full access so it might just exacerbate the looping

    In what way could it make the looping worse? I guess there is a thermal dynamic that I dont understand.

    Glass foam or EPS beads seem a lot safer.


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    #11
    Calahonda52
    Registered Users Posts: 12,194 ✭✭✭✭Calahonda52


    I said might, it's only a might.

    If you drive the panel out further from the inner leaf, without being able to fully fill the void behind, then you may make it worse.
    The other concern is that you don't know how far in the next joint is and you could blow the panel off the wall at the next joint.
    Based on the picture and 45 year in th business I would leave well enough alone and focus on what "battle space you can fully dominate" :)

    You are not domming this one.

    “I can’t pay my staff or mortgage with instagram likes”.



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    #12
    Yellow_Fern
    Registered Users Posts: 2,576 ✭✭✭Yellow_Fern


    Calahonda52 wrote: »
    I said might, it's only a might.

    If you drive the panel out further from the inner leaf, without being able to fully fill the void behind, then you may make it worse.
    The other concern is that you don't know how far in the next joint is and you could blow the panel off the wall at the next joint.
    Based on the picture and 45 year in th business I would leave well enough alone and focus on what "battle space you can fully dominate" :)

    You are not domming this one.

    I see what you mean. Much appreciated. Blowing the panel off would be a disaster. It is a frustrating case. The mason went to the effort of using the GFRP Wall Ties but left this gap.


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