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Roof insulation Q (condensation risk) value

  • 24-06-2009 11:46pm
    #1
    dafeens
    Registered Users, Registered Users 2 Posts: 9 ✭


    Folks,
    Got the following value from an insulation manufacturer in relation to the warm roof we will be constructing on our house.

    Single ply membrane
    200mm insulation
    vapour check
    18mm WPB deck

    U Value = 0.12 W/m2K
    Calculated 'Q' value under notional winter conditions over 60 days = 0.006kg/m²

    Are these values good or bad???


Comments

  • #2
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    Flat roof - right ?

    The designed U value is very good . The insulation must be PUR .
    Ask how the membrane is fixed . That may wreck the u value if metal fixings conduct heat through all that expensive insulation .
    Worse it will cause localised condensation and the fixings will fail by rotting the ply deck

    No idea what they mean by the Q value


  • #3
    dafeens
    Registered Users, Registered Users 2 Posts: 9 ✭dafeens


    Yep flat roof.

    Then insulation boards will be mechanically fixed and the membrane then fully adhered to the insulation.

    I think the 3 manufacturers boards that I am considering seem to be only available in PIR.


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