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Internal insulated plasterboard

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  • 08-11-2020 2:43pm
    #1
    porrige
    Registered Users Posts: 38 ✭


    Hi,

    I’m wondering if it’s worth to apply insulated plasterboard on the internal sides of external walls ?

    Reason I’m asking is because I’ve just realized the current spec for our walls only just meets 2011 regulations (applies to this build).

    Our house was specified as follows;

    Block walls with 150mm cavity - full fill bead insulation.
    Downstairs floor: 120mm solid insulation with 25mm insulation at wall perimeter with UFH
    Upstairs floor: 50mm solid insulation with 25mm insulation at wall perimeter with UFH.
    Upstairs ceiling; 150mm solid insulation between joists with 40mm insulated plasterboard at ceilings.
    Downstairs ceiling; 12.5mm plasterboard.
    Triple glazed windows.
    AirSource heat pump
    MVHR
    Airtightness at 3 (yes I know!)

    Current stage, first fix electrical complete, no floors, no plastering, insulation & airtightness complete (membranes & junctions taped)

    If applying the internal insulated plasterboard to external wall, I was thinking of spraying airtightness paint on block walls first, mechanically fixing the boards directly to wall & using PU foam sealing any gaps/junctions.

    Thanks in advance for opinions.
    Tagged:


Comments

  • Options
    #2
    MicktheMan
    Registered Users Posts: 2,823 ✭✭✭MicktheMan


    In the current spec, how are your external walls to be finished internally?
    Imo, you might well be better off to concentrate on getting the airtightness down towards 1 rather than adding extra insulation and introducing interstitial condensation risk as well as reducing your thermal mass materially.
    Is the house ready for a preliminary air tight test? Might be worth considering now if air tight measures are complete.


  • Options
    #3
    porrige
    Registered Users Posts: 38 ✭porrige


    MicktheMan wrote: »
    In the current spec, how are your external walls to be finished internally?
    Imo, you might well be better off to concentrate on getting the airtightness down towards 1 rather than adding extra insulation and introducing interstitial condensation risk as well as reducing your thermal mass materially.
    Is the house ready for a preliminary air tight test? Might be worth considering now if air tight measures are complete.


    Thank you.
    Yes will try to achieve best possible airtightness.
    External walls are rendered sand & cement plaster.
    I doubt thermal mass on walls would be significant ? as the walls do not come into direct contact with a heat source - perimeter wall insulation at floor level through out.


  • Options
    #4
    Biker1
    Registered Users Posts: 369 ✭✭Biker1


    Your walls act as a heat sink absorbing the ambient temperature not the heat source.
    If there is a lot of glazing this thermal mass is effective in regulating the temperature.


  • Options
    #5
    porrige
    Registered Users Posts: 38 ✭porrige


    Biker1 wrote: »
    Your walls act as a heat sink absorbing the ambient temperature not the heat source.
    If there is a lot of glazing this thermal mass is effective in regulating the temperature.


    Ok. Thanks. Windows are not considered large & are 0.8 u-value.


    Any opinions on op appreciated.


  • Options
    #6
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    porrige wrote: »
    Thank ytou
    Yes will try to achieve best possible airtightness.
    External walls are rendered sand & cement plaster.
    I doubt thermal mass on walls would be significant ? as the walls do not come into direct contact with a heat source - perimeter wall insulation at floor level through out.
    Assuming you need to comply with the current building regulations, and ignoring the reasons you are in this situation, what you are proposing in principle is ok, but you need to look at air-testing before the walls are dry-lined and Should push for a lower air-test result.


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