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Adding R value for air gap

Discussion in 'Floors, Stairs and Lofts' started by LabudMoj, 24 Sep 2011.

  1. LabudMoj

    29 Jul 2011
    Thanks Received:
    United Kingdom
    I was wondering if I can add the R values of an air gap and celotex above like in this:
    ~40cm between joists
    10cm | celotex |
    5cm | air gap |
    plasterboard -----------------

    So if I have an unvented air gap of 5cm at the bottom, the R value is 0.05m/0.024 (thermal conductivity of air) = 2.1

    10 cm of Celotex should have R value of ~ 4.5, so if I add these two I get 6.6, which satisfies building regulations (6.1 if I am not mistaken).

    I think this is the only way I can board my loft without adding more than one layer of anything above the joists.

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