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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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  1.  
    I have an air tightness issue in my kitchen which I'm trying to find the source of and remediate.

    The outside walls of my kitchen have a combination of outside lights, PIR sensors, outside sockets and a tap. There are 10 in total. I strongly suspect that the builders drilled nice big holes through the walls for the cables and didn't worry in the slightest about air tightness.

    The holes / cables are going to be difficult to get to from the inside as it would involve removing the plasterboard at best and kitchen units at worst which would be quite a big and expensive job. I was wondering if there would be a way to take the external light fittings off and remediate someway from the outside?

    The wall make up (from the outside in) is:
    Brick, air gap, Kingspan, breeze block, parge coat, dot and dab plasterboard.

    To make any difference I'm thinking I would need to try to seal in the breeze block layer, as close to the parge coat as possible. Is there anything I could inject?

    Suggestions from anyone who has done something similar gratefully received.
  2.  
    I completely sympathize, we had a kitchen fitted by fitters who thought that oversized cable holes in the walls and floorboards didn't need plugging if they could be concealed behind units. We only detected them the following winter by the cold draughts.

    Depending which units, it might be possible to unscrew them from the worktop and their neighbouring units, then wind down the height-adjustable feet, then slide the unit out? Have done this several places. It doesn't work for corner units.

    Eye level units are fairly easy to remove, check YouTube how. Same with 'built in’ appliances.

    Or cut out the back board of the unit to get at the area, replace later with a piece of veneered hardboard the whole size of the unit so the edges don't show.

    Then excavate your own hole in the plasterboard, plug the hole in the parge layer and reseal the plasterboard.

    Not tried this from outside but I suspect it will be hard to reach the inner block leaf to repair the airtight layer (parge).
    • CommentAuthortony
    • CommentTimeMar 25th 2021
     
    long nozzle on a foam gun

    it may be possible to identify air leakages behind the plasterboard using a thermal imager and then seal from inside

    good that you have a parge coat, you are one of the few shame about the holes
  3.  
    I suspect the holes were drilled with a long drill - straight line in one go. If this is the case you should be able to remove the outside fitting and inspect the handiwork. If it is one straight hole then I would have thought an extension on a foam gun would work.
    Does squirty foam attack cables the same way as EPS ??
    •  
      CommentAuthordjh
    • CommentTimeMar 25th 2021
     
    The difficulty will perhaps be seeing what you are doing. It might be difficult to see what's in the depths of the hole, and practically impossible to guide a nozzle to make an effective seal around the cable. But it's pretty easy to try that method I'd have thought and resort to Will's more proven technique if it doesn't work well.

    I don't believe foam does attack cables.
    • CommentAuthorMike1
    • CommentTimeMar 26th 2021 edited
     
    Foam might attack cables - best to check with the manufacturer.

    From https://nationalpolystyrene.com.au/wp-content/uploads/2020/11/PVC-Cables-in-Contact-with-Polystyrene-or-Bitumen-2.pdf :

    "Commonly used PVC plasticisers tend to exhibit solubility in polystyrene and polyurethane insulating
    materials, As a result of this there will be migration of plasticiser from the PVC compound where there is a
    direct contact between the two materials, this causes the PVC on the cable to become harder and more
    brittle. There is also potential for plasticiser migration into bituminised building paper, causing the bitumen
    to soften and flow.

    However this problem has been known about for years; surely the standards for cables must have been revised by now? Anyone have access to the relevant EN /BS document?
    • CommentAuthorrevor
    • CommentTimeMar 26th 2021
     
    No cables in EPS other insulants ok but restriction on how much cable can be buried in it. Limit is 500mm in one power circuit but lighting can be more as less likely to overheat but depends on load.

    Don't know whether this will work but as you can remove the fitting could you get an endoscope in the hole to see what is going on. Could you get a length of conduit or similar to bridge across the cavity. Put some foam on the end and push through to the interior wall so sealing at that point then fill around the cable in the tube at the outer wall and finish flush to the brick work. No need to fill the tube. Just something to try.
  4.  
    Thanks for all the comments.

    I'm pretty certain that the holes will be straight, so I was thinking of foam gun but I wanted to get the collective wisdom of the forum. It was a good point to check that the foam is suitable for using with cables.

    I have an endoscope, but I'm not sure if the holes will be big enough for the camera and the electric cable but I'll see.

    Doing it blind won't be ideal, but I should be able to calculate the width of the brick, cavity, Kinspan and breeze block to know how far to push in the foam gun extension.

    I'm just hoping that this is the source of my issue as otherwise the investigations will get a lot messier (and more costly) but I think this will be worth doing regardless.
    •  
      CommentAuthordjh
    • CommentTimeMar 26th 2021
     
    Posted By: Mike1Foam might attack cables - best to check with the manufacturer.

    Fromhttps://nationalpolystyrene.com.au/wp-content/uploads/2020/11/PVC-Cables-in-Contact-with-Polystyrene-or-Bitumen-2.pdf" rel="nofollow" >https://nationalpolystyrene.com.au/wp-content/uploads/2020/11/PVC-Cables-in-Contact-with-Polystyrene-or-Bitumen-2.pdf:

    "Commonly used PVC plasticisers tend to exhibit solubility in polystyrene and polyurethane insulating
    materials, As a result of this there will be migration of plasticiser from the PVC compound where there is a
    direct contact between the two materials, this causes the PVC on the cable to become harder and more
    brittle. There is also potential for plasticiser migration into bituminised building paper, causing the bitumen
    to soften and flow.

    However this problem has been known about for years; surely the standards for cables must have been revised by now? Anyone have access to the relevant EN /BS document?

    That's an unfortunate quote you found - it seems to be wrong.

    https://www.voltimum.co.uk/articles/q-day-should-pvc-cable-be-contained
    https://www.basec.org.uk/

    There are cables that are resistant to attack by polystyrene but the simpler answer is usually to put the cables in a conduit.
    • CommentAuthortony
    • CommentTimeMar 26th 2021
     
    I dont see pu foam containing plasticisers that could plasticise pvc cables. the problem is real but not major

    insulating a cable going to an outside light will not be a problem if it is LED
    • CommentAuthorMike1
    • CommentTimeMar 26th 2021 edited
     
    Posted By: djh
    That's an unfortunate quote you found - it seems to be wrong.

    I'd like it to be, but here's another company saying the opposite:
    https://www.prysmiancable.co.nz/insight/pvc-cables-recommended-installation-practices/

    "It is recommended that installers ensure general market PVC insulated and sheathed electrical cables be installed in such a manner that they do not come in to direct contact with aromatic polymers (e.g. styrene, Styrofoam and polyurethane), bituminized papers and waterproofing"

    Maybe it's a bigger concern in the southern hemisphere than in the northern.

    Unfortunately I can't find anything on the BASEC site in either direction.
    • CommentAuthorMike1
    • CommentTimeMar 26th 2021 edited
     
    Posted By: tonyI dont see pu foam containing plasticisers that could plasticise pvc cables.
    It's the other way round - plasticisers from PVC cables migrating into other materials.
    • CommentAuthortony
    • CommentTimeMar 27th 2021
     
    Yes, sorry, still can’t see them migrating int pu foam
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