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Advice - insulate suspended floor or ?

  • 14-07-2022 12:37am
    Registered Users Posts: 89 ✭✭ Ropo


    Would really appreciate some input. Budget running tight. 35 sqm of suspended floors , should we insulate between the rafters and lay mdf or would a good underlay below lamiante floor and seal to the skirting in affect do the same job?

    Attic is being done and walls are drylined. New extension has concrete floors.

    Appreciate how much would you expect to pay for insulation and mdf relaid ?



  • Registered Users Posts: 1,300 ✭✭✭ dathi

    is the 35sqm of floors on the ground floor or are you talking about floors in the attic?

  • Registered Users Posts: 89 ✭✭ Ropo

    Hi its ground floor

  • Registered Users Posts: 751 ✭✭✭ C. Eastwood

    A timber suspended ground floor needs through underfloor ventilation to prevent timber decay from occurring.

    It’s very important that whatever you do does not lead to Rot occurring in the timbers.

    Usually because of the underfloor ventilation, draughts will occur up through the open Tongue and Grooved joints in the flooring boards, and also from the margins of the floor up under the skirting boards. These draughts will cause heat loss by Convection. Sealing all of these draughts will have a big savings in heating and will reduce heat loss.

    Remove the skirting boards and seal the gaps under same between the flooring and the walls with expanding foam.

    A sheet of polythene on top of the T&G flooring boards, turned up the walls 75 mm and mastic it on to the walls before fitting the new skirting boards will prevent all of this heat loss by Convection.

    Fit new laminate on underlay over the polythene before fitting new skirting boards.

  • Registered Users Posts: 89 ✭✭ Ropo

    Thanks for the reply.

    So either option : insulate between the rafters with Kingspan v polythene sheet as described above give them same heat loss prevention ?

    We aren't looking for air tightness just to save energy as much as we can .

  • Registered Users Posts: 30,752 ✭✭✭✭ Lumen

    Air tightness saves you money. There's no point in putting down insulation if the cold air just blows around it.

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  • Registered Users Posts: 751 ✭✭✭ C. Eastwood

    Totally agree. Heat will leave the building anytime by Convection rather than Conduction.