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Yes, we just did it a couple of weeks ago.
What @Sumo said basically, although we used different materials, basically a budget version of this best-practice guide: https://www.ecologicalbuildingsystems.com/post/suspended-timber-floor-insulation-best-practice-installation-guide
Our build-up is (top to bottom):
Protect Barri-Air Membrane (sits on top of joists and insulation, comes with integrated airtightness tape along one edge, MUCH cheaper than the Pro-Clima stuff) https://insulationmerchant.com/products/protect-barriair-vapour-control-layer-with-integrated-tape-1-5-x-50m
150mm Knauff mineral wool insulation (MUCH cheaper than hemp/wood fibre, MUCH easier to install than rigid PIR, vapour-permeable and won't end up with gaps over time as the joists move)
Standard cheapo roofing membrane (whatever was cheapest in the local builders merchants) wrapped up and over the joists, secured with battens.
All taping done using 'PHS Argo Plus' airtightness tape, using spray-primer when adhering to brick behind skirting boards. This tape is less than half the price of the proper Tescon Vana stuff, and it all adds up as you end up using A LOT of it: https://passivehousesystems.co.uk/product/phs-argo-plus-joining-tape/
The materials cost less than a third of the 'proper' Pro-Clima and hemp bits recommended in the article above, and will be functionally the same.
Be prepared to remove a metric fuckton of rubble/rubbish from your floor voids; ours took up three full skips and cost a fortune in labour to shift. Took much longer to delete the mountains of rubble than it did to actually install the insulation.
Also, sadly less than 20% of our nice original Victorian floorboards were salvageable; most of them splintered into dust whilst trying to carefully remove. Shout out to @Fox for saving the day with local spares.
I've got quite a bit of the Barri-Air membrane left over if you want it.
ectoplasmosis-
Thanks! I have also read that guide as it goes, good to know if you've done it and the hints on cheaper stuff are really helpful.
Just trying to work out if we pull them all up and gamble on saving the boards (when we pulled out 2msq of boards in an en suite room upstairs they all came out intact, but maybe that's easier as they were shorter boards?) or try to add insulation from underneath (+ good to know @Sumo managed it so it is doable).
Will give you a DM on the membrane if we go ahead, trying to come up with our plan asap cheers!
Also how come you needed to excavate so much stuff if you were pulling the boards - was there just insufficient space for air circulation etc underneath?
andyfallsoff
Who on here has insulated under floorboards - any recommendations on what to use + whether it is realistic for me to hope I can salvage / reuse the lovely 1920s floorboards in the house at present, or will they all split and be useless?