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beads versus foam for cavity in redbrick - the porous question

  • 06-04-2013 9:05am
    #1
    laugh gov
    Registered Users Posts: 19 ✭


    Hi folks - looking for a little help. I can almost find the answer on previous threads but need convincing / reassurance

    We are retro a 1993 red bricked bungalow which has a cavity filled with flimsy white board at present. We are going to fill the cavity from inside and then dry line with 82 mm insulated board internally.

    The question of what to fill the cavity with has come up - foam versus bonded beads

    From what I understand here are the pros and cons

    foam
    pros
    lower u value
    better air tightness
    fills the gaps between the filmsy aeroboard as pumped in under pressure

    Cons
    not on grant
    dear - ours is 1500 e dearer
    ?water permeability
    not certified in Ireland

    bonded beads
    pros
    tried and tested
    cheaper
    on the grant
    no water permeability

    cons
    may not fill the cavity as aeroboard kind of gets in the way
    higher u value


    My concerns are if I go for foam how real is the risk of water transfer. Whereas if I go for the beads will the cavity be underfilled dramatically thus defeating the purpose. I know that there is a cash concern here which is always real but which long term would be value for money? I know red brick is permeable. Is this a factor?

    Other information that may be important we are trying for as good air tightness as possible - expanding foam to eves of atic. Also going for mechanical heat ventilation and triple glazing.

    Hope I posted in correct place as first post - have been reading forums for a long time - class tool.

    Thanks for you opinions and expertise :o
    Tagged:


Comments

  • #2
    muffler
    Registered Users Posts: 45,803 ✭✭✭✭muffler


    laugh gov wrote: »
    not certified in Ireland
    You have answered your own question :)


  • #3
    MicktheMan
    Registered Users Posts: 2,823 ✭✭✭MicktheMan


    Why are you considering using a product which is not certified for use here?
    Why pumping from the inside when there is already an insulation board fixed to the inner leaf? If this board gets disturbed by the drilling/pumping, you may well end up worse off insulation wise.
    Where is the house located and is it exposed? This may inform the answer whether it is a good idea at all to full fill brick cavities.

    Have you had your proposed wall make up modelled for moisture build up over time?

    Regarding airtightness:
    1 Who is advising to close the eves ventilation?
    2. who is advising expanding foam as airtightness barrier?

    Do you have any professional input on this project?


  • #4
    laugh gov
    Registered Users Posts: 19 ✭laugh gov


    thank you taking the mick

    Why not consider something thats not certified for use here - Irelands hardly world leading in anything and is very conservative. I think it is certified in uk which has the same climate. Hence I pose the question is it worth it?

    The house has a sheltered site

    not sure what you mean by "Have you had your proposed wall make up modelled for moisture build up over time?" this is a retrofit

    No one is advising to close the eves ventilation. No one is advising foam as an airtightness barrier. Yes there is a professional involved - I thought Id do my own research.


  • #5
    laugh gov
    Registered Users Posts: 19 ✭laugh gov


    muffler wrote: »
    You have answered your own question :)
    Have I?


  • #6
    MicktheMan
    Registered Users Posts: 2,823 ✭✭✭MicktheMan


    laugh gov wrote: »
    thank you taking the mick
    Nobody's "taking the mick"
    laugh gov wrote: »
    Why not consider something thats not certified for use here
    Why don't you ask your bank or insurance company that you are thinking of using un-certified products. Would you buy a house that has un-certified materials in the walls?
    laugh gov wrote: »
    not sure what you mean by "Have you had your proposed wall make up modelled for moisture build up over time?" this is a retrofit
    Building physics. Having insulation on two different planes increases substantially the risk of interstitial condensation and moisture buildup.

    laugh gov wrote: »

    No one is advising to close the eves ventilation. No one is advising foam as an airtightness barrier.
    Good.... then don't do it.


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  • #7
    laugh gov
    Registered Users Posts: 19 ✭laugh gov


    Sorry micktheman - Misread

    Its a fair cop

    I think you are saying what I was thinking - stay away from foam and go for beads (or nothing in cavity). I had a look at it again today and the aeroboard is fitted to the inner leaf which is block lined (outer red brick). Is the danger of disturbing the boards off and causing us to be worse off substantial when drilling from inside in your opinion?

    Building physics. Having insulation on two different planes increases substantially the risk of interstitial condensation and moisture buildup.

    Interesting I have to say. Was not aware of this.


  • #8
    therightangle
    Registered Users Posts: 85 ✭✭therightangle


    MicktheMan wrote: »
    Building physics. Having insulation on two different planes increases substantially the risk of interstitial condensation and moisture buildup.

    Does anyone have a reference for this?
    I would imagine it is still better than keeping all the insulation on the inside?
    Granted it might be true if comparing cavity+ext with just external.
    But its hardly true if comparing cavity+int with just internal?


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