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Attic conversion insulation questions

  • 31-07-2015 12:33pm
    #1
    wtd2008
    Registered Users, Registered Users 2 Posts: 204 ✭✭


    Hi,

    We are in the process of converting the attic of our 3 bed semi. A builder was recommended who did a conversion for a neighbour.

    My concern is about the insulation depth, he quoted for 50mm foil-back Kingspan insulation to all exterior walls and ceilings and 12.5 foil back slabs to all walls and ceilings.

    Is this going to be enough? We already have floor insulation, should this be taken up the let the heat rise or left in place?

    Just looking at some other threads the 50mm seems very little. The neighbour only has it done since February so hasn't had the test of a cold winter yet.

    What's your advice lads?
    Thanks


Comments

  • #2
    Citroen2cv
    Registered Users, Registered Users 2 Posts: 291 ✭✭Citroen2cv


    The 50mm foil-back is probably insulated plasterboard for the party wall.
    I would imagine he is going to pull up the insulation in the floor, and insulate between the rafters instead.


  • #3
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    suggest leaving the insulation under floor, for acoustic reasons

    what U value will he achieve on the underside of the ceiling (that's what you should care about - not the absolute depth)


  • #4
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    wtd2008 wrote: »
    Hi,

    We are in the process of converting the attic of our 3 bed semi. A builder was recommended who did a conversion for a neighbour.

    My concern is about the insulation depth, he quoted for 50mm foil-back Kingspan insulation to all exterior walls and ceilings and 12.5 foil back slabs to all walls and ceilings.

    Is this going to be enough? We already have floor insulation, should this be taken up the let the heat rise or left in place?

    Just looking at some other threads the 50mm seems very little. The neighbour only has it done since February so hasn't had the test of a cold winter yet.

    What's your advice lads?
    Thanks
    How much space is in the attic? I'd be definitely looking for an air-tightness membrane on the inside the insulation, this would ideally be tapered and sealed to the wall plate- this is difficult but IMO necessary, other option include foam but ventilation is important. All these things need to be considered as well as insulation. Separately the Ventilation of the internal space should be considered as well as window etc as part of the overall fire escape requirements.
    http://www.environ.ie/en/DevelopmentHousing/BuildingStandards/PublicationsDocuments/FileDownLoad,1657,en.pdf

    I'd double the insulation thickness. IMO there's several major surveying/ construction details required (that should be agreed) before a builder starts on an attic conversion. For instance does the stairs and first landing construction meet the regs?


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