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Airtightness/vapour barrier on Insulated drylining.

  • 18-07-2023 1:31am
    Registered Users Posts: 7,042 ✭✭✭

    I'm renovating a mass concrete 50's bungalow atm.

    Currently I'm preparing for slabbing and doing airtightness.

    All windows are taped and installing the airtight/vapour barrier (isover vario km duplex uv) membrane on the ceilings.

    All external walls are drylined with 75x50 timber studs, filled in between with 75mm PIR insulation. It will be finished with a 50mm (total) insulated slab and skimmed.

    I'm intending taping all the drylining junctions where it meets the floor, ceiling and internal walls. There is a ventilated space between the back of the drylining and the external walls. Ceilings are getting the same slabs with 200mm Knauf Earthwool in the attic.

    There is an MHRV system installed.

    My question....I've been told that an airtight/vapour barrier is not required/advisable on the drylined walls as the slabs have an integrated vapour barrier and having 2 could cause condensation. Is that the case?

    I just don't was to miss an opportunity to improve airtightness but don't want to create another problem.