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Insulating Hollow Block Walls

  • 19-06-2014 8:13pm
    #1
    HappyNoel
    Registered Users Posts: 41 ✭


    Hi Folks,


    Just a question about a house I'm buying that's been built with 9 inch hollow blocks.

    I'm looking to improve the house's u-value and lots of people have recommended I get the house externally dry lined.

    However, if I get it dry lined, would I still need to get insulation pumped into the hollow blocks as well? It strikes me that if I don't, the heat will pass through the inside of the block and as soon as it meets the hollow, it'll start to rise up and disappear. Would I need to pump the blocks AND externally dry line the house to do the job properly, or am I misinformed?

    Any suggestions appreciated.


Comments

  • #2
    sydthebeat
    Subscribers Posts: 41,915 ✭✭✭✭sydthebeat


    you cant pump hollow blocks.... you actually make the situation worse.

    either insulate internally or externally


  • #3
    HappyNoel
    Registered Users Posts: 41 ✭HappyNoel


    sydthebeat wrote: »
    you cant pump hollow blocks.... you actually make the situation worse.

    either insulate internally or externally

    Thanks - I had planned to externally insulate the house all right, just wondering if it would be effective without pumping the walls too. Didn't think it would be worse though! Does it cause dampness or something?


  • #4
    sydthebeat
    Subscribers Posts: 41,915 ✭✭✭✭sydthebeat


    HappyNoel wrote: »
    Thanks - I had planned to externally insulate the house all right, just wondering if it would be effective without pumping the walls too. Didn't think it would be worse though! Does it cause dampness or something?

    the reason i wouldnt attempt to pump the walls is because of the amount of pumping needed. Unless you pump ever hollow you can never be assured of filling the gaps. for example, a hollow block wall of 10m x 2.4 m would need 475 separate drill holes !!

    if you are externally insulating, the most important point is to ensure there is a continuous sealing of the top of the hollow block wall. This may already exist, you need to check.
    This is because if you do not, the hollow blocks can vent vertically and out into the roof / eaves. This would be detrimental to your external insulation system.

    this vertical venting actually works to keep the blocks dry in a typical single leaf wall. If you pump the hollows (and dont use external insulation) then you actually remove this natural drying. You also increase the intensity thermal bridges across the blocks when you pump the hollows. every web becomes a river for heat to flow through... rendering the pumping useless.


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