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Block reveals in nee houses and cold bridging

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  • 15-05-2024 7:51pm
    #1
    Yellow_Fern
    Registered Users Posts: 2,590 ✭✭✭


    Hi all,

    Driving around seeing new housing I have spotted the method where reveals are formed by having a half block crossing the cavity. I had thought this method had lost favour due to cold bridging concerns?

    Btw in renovations, is it every removing these perpendicular blocks or is too much trouble?



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    #2
    Biker1
    Registered Users Posts: 380 ✭✭Biker1


    Not common or best practice. Blocks returned to within 75mm of the outer leaf and PIR insulation used to fill the gap would be a good detail. Reduces thermal bridging to a minimum, leaves a solid block to fix window straps and makes it easier for the airtightness tape to get a good bond.



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    #3
    the_amazing_raisin
    Registered Users Posts: 11,066 ✭✭✭✭the_amazing_raisin


    I seem to remember Roadstone have some insulated blocks for this purpose, pretty sure they're supposed to prevent cold bridging

    Maybe that's what was seen here?

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost



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    #4
    Biker1
    Registered Users Posts: 380 ✭✭Biker1


    https://www.boards.ie/discussion/comment/122142945#Comment_122142945

    The Roadstone blocks you are referring to would only reduce the thermal bridging slightly. You would still need a thermal break between the inner and outer leaf to make a real difference.



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    #5
    Yellow_Fern
    Registered Users Posts: 2,590 ✭✭✭Yellow_Fern


    https://www.boards.ie/discussion/comment/122142945#Comment_122142945

    Could be this. I iwll try to get a picture



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    #6
    Yellow_Fern
    Registered Users Posts: 2,590 ✭✭✭Yellow_Fern


    Here is an example taken today

    IMG_20240527_181145.jpg



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    #7
    Mellor
    Registered Users Posts: 39,168 ✭✭✭✭Mellor


    https://www.boards.ie/discussion/comment/122191328#Comment_122191328

    That block is most likely not fully crossing the cavity. There should be a section of full fill insulation across the reduced cavity. I would also want it to be an AAC block to reduce the thermal bridge. It's certainly not the optimal detail, but I'd still expect to find it used in spec housing. It's still included in acceptable construction details 2021 (below)

    https://i.imgur.com/txk4ugt.png



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    #8
    sydthebeat
    Subscribers Posts: 41,291 ✭✭✭✭sydthebeat


    https://www.boards.ie/discussion/comment/122191978#Comment_122191978

    a resistance of 2.4 m2K/W equates to about 53mm of PIR insulation

    it doesn't look like they have left enough gap in that photo.

    there only looks to be about a 100mm cavity as well, so i wouldn't be surprised if the spec here is to internally insulate with insulated plasterboard.



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    #9
    Mellor
    Registered Users Posts: 39,168 ✭✭✭✭Mellor


    https://www.boards.ie/discussion/comment/122192953#Comment_122192953

    That's fair, was more so getting at the idea that that older style of closer is still about. Rather than endorsing the build in the photo (which is questionable around the lintel also), or anywhere really.

    If we were being totally fair. The block park of the closer should contribute too. But even with a quinlite, 75mm AAC + 25mm PIR gets you to 1.6m2K/W at best. That approach it really only viable for cavitys in excess of 100mm. Regardless of widths it will never match a full insulated closer.



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