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Insulating wide valley

Discussion in 'Roofing and Guttering' started by bsr, 16 Jan 2019.

  1. bsr

    bsr

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    Hello

    See the attached picture. I have a wide lead valley (blue) running the width of my house where two pitched roofs join. The valley is about 400mm wide.

    I have insulated the rest of the roof space with 300mm mineral wool. What should I do here? Can I fill with mineral wool up to the plywood deck (red), or do I need to leave a space for ventilation? Should I use an alternative product? Normally I would leave spaces at the eaves to allow cross-ventilation, but there is none here since there is a pitched roof on both sides.

    Thanks


    bsr
    wall insulation.png
     
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  3. bsr

    bsr

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    Anyone?
     
  4. noseall

    noseall

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    Can't see the point insulating there. You need it closer to the inside of the room.
     
  5. datarebal

    datarebal

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    Condensation is likely to form n the under side of the lead. Slip some pir board under with no gaps
     
  6. bsr

    bsr

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    Noseall, I'm not sure what you mean. The valley is very close to the rooms. At the moment I have only plasterboard, 300mm air space and then the valley. That's why I want to insulate it, but without causing any damp problems.
     
  7. noseall

    noseall

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    The insulation needs to be directly beneath the plasterboard.
     
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