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Adding second level of insulation to wall cavity

  • 25-11-2020 1:26pm
    #1
    JimFin
    Registered Users, Registered Users 2 Posts: 118 ✭✭


    Hi,

    Unusual insulation query! I have a 10 year old house which has a 100mm cavity with 60m thick foil backed insulation. The internal walls all have cosy board. I am doing some work on the house at present and am considering pumping the remainder of the cavity with bead.

    Does anyone have any views on whether this makes sense or can I expect it to have much impact on heat retention?


Comments

  • #2
    MicktheMan
    Registered Users, Registered Users 2 Posts: 2,880 ✭✭✭MicktheMan


    JimFin wrote: »
    Hi,

    Unusual insulation query! I have a 10 year old house which has a 100mm cavity with 60m thick foil backed insulation. The internal walls all have cosy board. I am doing some work on the house at present and am considering pumping the remainder of the cavity with bead.

    Does anyone have any views on whether this makes sense or can I expect it to have much impact on heat retention?

    More than likely not.

    Reason being, based on your wall description, your primary heat loss mechanism is likely due to convection losses (draughts) rather than conduction losses which insulation addresses.


  • #3
    denismc
    Registered Users, Registered Users 2 Posts: 1,584 ✭✭✭denismc


    Sounds like you may have a timer framed house. If so then pumping the cavity would not be a good idea


  • #4
    JimFin
    Registered Users, Registered Users 2 Posts: 118 ✭✭JimFin


    Thanks for the replies, its a concrete house. With some work going on with the house it seems like the best time to do it if I am to do it at all.
    My thinking is that the current insulation may have gaps in it that the bead will flow into and give more complete solution.


  • #5
    poker--addict
    Registered Users, Registered Users 2 Posts: 1,773 ✭✭✭poker--addict


    No expert but given what is already in place it sounds like the law of diminishing returns would apply in that the gain at this stage would be minimal compared to cost, could be worth putting the investment into another upgrade though.

    😎



  • #6
    JimFin
    Registered Users, Registered Users 2 Posts: 118 ✭✭JimFin


    Just a quick update in case anyone benefits from it.

    Had a good chat with an experienced man in the trade who advised of the risks of doing this. He said to pump insulation in he would need at least 50mm of cavity space available. The reason for this is that when drilling the block many blocks will flake off a large piece as the drill goes into the cavity, this waste needs good clearance to fall to the ground and if it got wedged it could be a real risk to conducting dampness in.

    All in all he said there was also a strong chance the t additional insulation would only make a marginal improvement on the dense insulation already in the cavity. Based on his 10 years in the business he would be reluctant to take it on. I think I will pass on the work!


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