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Poroton blocks + External Insulation

  • 07-06-2011 2:20pm
    #1
    coolashaker05
    Closed Accounts Posts: 1 ✭


    Hi All,

    I will be starting a new build in the comming months & plan to build the house with Poroton blocks + external insulation.

    I will be using a T8 poroton block that will give me a U value of .21 & will be aiming to reduce this down to about .15/.16 with the extrnal wall insulation.

    Many suppliers seem to be recommending expaned polystyrene for the external walls. (they have said it is breathable to a point, is this true?) Given that breathabliliy is one of the chief benefits of the Portoton system, I am wondering if this willl be lost due to nature of the insulation.

    There are breathable alternatives available for the external insulation, however ideally i would like to have waterproof exteranl walls.
    Am I asking too much for a wall to be breathable yet water proof from the outside. Is there any way of acheiving this? Or would you reccomend an alternative way of going about it.

    many thanks


Comments

  • #2
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    what about a hemplime mix

    or

    rigid mineral wool or insulated wood insulation, battened and cross battened with cement fibre boards plaster painted, leaving vent gaps at under eaves and at the base of the wall (basically some variation of a rain-screen cladding system)

    alternatively, you could go for mineral wool board with cement render from one of the main three EWIS manufacturers (mainly specified on old stone walls to allow for some level of a Vapour open system


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