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Garden Room insulation.

Discussion in 'Building' started by commando3, 30 Sep 2021.

  1. commando3

    commando3

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    Im currently building a garden room but I have a question about the insulation between the wall studwork.
    Im using 4 x 2 cls24 timber. If I use 100mm pir boards for insulation how do I go about the electrical wiring channels for the cables and sockets?
    Can i cut into pir boards?
    Or, should I use 75mm or 80mm pir insulation boards leaving me space between the pir boards and plasterboard? Would it be ok to have an air gap here?
    TIA.
     
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  3. Mr Chibs

    Mr Chibs

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    It’s not advised to route cable into insulation.

    You can leave a gap as you’ve suggested, but you may have to deal with condensation/ventilation.

    You could add battens in the inside (warm side) to make a void for cables, then plasterboard.

    Or use conduit and surface mount on top of plasterboard... depending on look you are going for.
     
  4. commando3

    commando3

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  5. commando3

    commando3

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    Many thanks for your reply. The interior finish will be plasterboard and skimmed and all sockets flush so surface mounted conduit on the plasterboard is ruled out.
    I'm thinking now of 100mm insulation board but where the cables run- use 75mm thus creating a channel? There would be minimal loss in insulation ?
    Would this work? I can then cover the studwork with vapour barrier before plasterboard.
    Would there be a reason why I couldn't cut into the insulation board and fix conduit into it?
    Cheers
     
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  7. ^woody^

    ^woody^

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    Cut a slight recess in the board and put some cable capping in the opposite way round. This protects the cable from the foam, but the closeness to the surface gives no heat issues
     
  8. Sorry, but that isnt true.

    Plus this is probably notifiable, so using an electrician (who will know how to size cables) makes most sense anyway.
     
  9. commando3

    commando3

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    Looking on YouTube I can see varied ways that people are putting in 1st fix electrics into garden rooms. The latest one being a 18th edition spark fixing the cabling into the corners between the outer osb and the studs then cutting the lengths of isulation on the long edges to cover the cables.
     
  10. You can bury cables fully enclosed by as much insulation as you like - you just have to make sure they are the right size.

    Simple physics - cables have resistance, thinner ones more, fatter ones less. Resistance means they heat up when current flows so if insulation is going to keep them warm you need fatter ones.
     
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