insulation question

Discussion in 'Builders' Talk' started by Kaylg, Sep 20, 2018.

  1. Kaylg

    Kaylg Member

    I am looking to use 25mm foiled insulation internally inbetween battens on external facing walls (cavity - inner leaf) and then plasterboard over.

    Celotex, kingspan, xtratherm, etc...

    To the untrained eye, they all look very similar and even reading the technical specifications i can't see much difference.

    Can I use something like this (labelled cavity)

    Or 'pitched roof board'

  2. rogerk101

    rogerk101 Screwfix Select

    I never waste my time with foiled insulation. I just use regular insulation and then add my own vapour barrier wherever it needs to be. When you use foiled insulation, especially between battens, joists or rafters, you still have to issue of what to do at the edges. Better to get them in with as snug a fit as possible, and then put a continuous vapour barrier over the whole lot ... rafters/joists/battens PLUS insulation. Only in that way will you create a true continuous vapour barrier.
  3. Kaylg

    Kaylg Member

    What do you class as regular insulation, rockwool?
  4. rogerk101

    rogerk101 Screwfix Select

    No. Not rockwool. I only ever use rockwool between ceiling joists, and even then it's suboptimal in that you can get better insulation characteristics out of extruded polyurethane panels of the same thickness.
    I use extruded polyurethane panels from the likes of Celotex, Quintherm, etc. They come in board sizes up to 1200 x 2400 and in thicknesses from as thin as 20mm right up to 200mm. I usually buy it in 100mm thick and double up to 200mm but with staggered joints.

    When I did up a house recently I bought a truckload of new, but slightly damaged panels of varying thicknesses, and saved myself a fortune. Since most of the boards get cut into much smaller pieces anyway, it's easy to just cut off some damaged edges, and you end up with pieces that are just as good as the brand new stuff.
    DIY womble likes this.

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