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    • #63348
      X Wookey
      Participant

      {no sign of post so trying again – maybe this will be here twice?]

      My 1960s retrofit already has concrete floors so I’ve not done this personally, but as no-one else has offered an opinion, here’s mine.

      Unless the space is too deep to make it practical, I’d fill it in. so you can get a properly insulated floor with some thermal mass. and get decent airtightness. Building control people get very difficult about airbricks, airtightness and suspended timber floors so getting rid of it is both technically and ‘politically’ better.

      Hopefully the space is just right for 200-300mm of insulation. I default to XPS rather than PUR underground just in case it ever got soaked (flooding), but that’s carbon-intensive too, so if you’d prefer to avoid that foamglass agreegate is very green (but also expensive when I looked). https://www.mikewye.co.uk/product-category/brands/geocell-foam-glass/ You’d just pour that in instead of the hardcore, then put a floor on top. Lithotherm UFH floor blocks directly on top of the foamglass is one way to do concreteless solid floor: https://www.backtoearth.co.uk/product/underfloor-heating-tiles/ I’ve not tried it myself but I’ve seen one and it looks like a reasonable plan. Backtoearth are great so I’d certainly have a chat to them about it.

      You could take the view that having this nice space to fill in with some insulation is a bonus. Dealing with an existing concrete floor is a pain because digging it up is a big job and insulation on top is technically limiting, especially with UFH.

    • #63347
      X Wookey
      Participant

      My 1960s retrofit already has concrete floors so I’ve not done this personally, but as no-one else has offered an opinion, here’s mine.

      Unless the space is too deep to make it practical, I’d fill it in. so you can get a properly insulated floor with some thermal mass. and get decent airtightness. Building control people get very difficult about airbricks, airtightness and suspended timber floors so getting rid of it is both technically and ‘politically’ better.

      Hopefully the space is just right for 200-300mm of insulation. I default to XPS rather than PUR underground just in case it ever got soaked (flooding), but that’s carbon-intensive too, so if you’d prefer to avoid that foamglass agreegate is very green (but also expensive when I looked). https://www.mikewye.co.uk/product-category/brands/geocell-foam-glass/ You’d just pour that in instead of the hardcore, then put a floor on top. Lithotherm UFH floor blocks directly on top of the foamglass is one way to do concreteless solid floor: https://www.backtoearth.co.uk/product/underfloor-heating-tiles/ I’ve not tried it myself but I’ve seen one and it looks like a reasonable plan. Backtoearth are great so I’d certainly have a chat to them about it.

      You could take the view that having this nice space to fill in with some insulation is a bonus. Dealing with an existing concrete floor is a pain because digging it up is a big job and insulation on top is technically limiting, especially with UFH.

    • #37381
      X Wookey
      Participant

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    • #37318
      X Wookey
      Participant

      Viking house has used and praised them on the green building forum. 'fraid I can't find the post right now.

    • #36748
      X Wookey
      Participant

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    • #36779
      X Wookey
      Participant

      Proclima Tescon is _much_ better tape than aluminium. It's stretchy so allows for movement and it's very sticky so it'll stay stuck for decades. I wouldn't use foil tape for sealing to anything other than foil/smooth plastic surfaces and I wouldn't use it where there is any possibility of differential movement. I'd avoid using it anywhere where it won't be held in place by something on top.

      So for sticking ply boxes together I'd not use foil tape – it won't stick very well atall, and there could be slight movement which would tear/fatigue it. I'd either use Tescon if taping, or as has been suggested, glue/goop between abutting boxes. This latter is probably the best plan.

      Yes Tescon is expensive, but it's also excellent – it's good value IMHO.

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