tenovus

Ah that would be very tempting! Sadly, I think we've decided to avoid options with much floor build up because the room is open plan with the dining room which has some much nicer boards that we're likely going to keep in place so we don't want the step up. A rod for our own backs... Thanks for the inspiration though! I too have access to some free mineral wool - mine apparently cleared from a raided weed farm!

Thanks everyone for all the wisdom - it's like winding up a series of clockwork experts and watching them go! Mega reply incoming... On ventilation, this is something I've entirely internalised and become paranoid about so will be making sure of it! As it stands, it feels very ventilated under there but I'll be sure to keep it flowing! When it comes to wall ventilation under the floors, would this be done internally? Apologies for the dodgy sketching - I'm yet to perfect the fast draw! The plan would be to sandwich the membrane between the OSB and the joist then staple and batten to the bottom of the OSB to keep the hammock taut across the gap. Thanks, Nick! Just on the VCL - would there be an issue with using a polythene VCL sheet over PIR so that I don't need to get too exact with the foil tape or does that create issues by having two impermeable layers on top of each other? Luckily no gas pipes in this part of the house (besides the long empty coal gas ones) and, fingers crossed, will be going to an ASHP in future. Much as the idea of a massive balloon of natural gas under the lounge sounds tempting...

Thanks for this - will seek that foam out!

Thanks for this Iceverge! Hadn't considered something so OSB based! Definitely allows me to make use of the massive bags of loftroll I have to hand! Is there a risk of condensation with the OSB at the bottom? And do you think even when glued UFH chipboard will work as a vapour barrier or do you think I'd need to find one with a specific coating? I'm tempted to try a version of the above but with a breathable membrane at the bottom instead of the box base. I guess it wouldn't have quite the same structural improvement!

Ah I see! Absolutely, it should all be accessible for making sure that membrane is airtight. I was thinking I could drape it over some of the joists too though that's not easily shown in the Ubakus. I'd read some people suggest it on similar threads but worried about messing too much with the house as it's managed the last 170 years fairly well! The space would remain cold and ventilated. We also have a small cellar that goes a little deeper than the crawlspace and, as a semi, next door's crawlspace is adjacent to ours - I'm not sure if that has implications for putting in a solid floor.

I can, but I'll be taking the boards up anyway.

Hello all! I'm looking to insulate a Victorian suspended timber floor so I can stop heating the dirt. I'm planning to take most of the boards (not original) and replace with UFH chipboard panels. As my joists are 100mm deep (if I'm lucky - some are shallower), I don't think the Ecological Building Systems route alone is going to be quite good enough. I have some 100mm PIR to hand and plenty of crawlspace. I've put together a bit of a proposal on Ubakus which I'd love some thoughts on. Essentially using woodfibre board to extend the joists, hanging a breathable membrane off those, filling those hammocks with loose fill or STEICOflex (or eq) then a layer of PIR at the top. I'd hope this would combine the hygroscopic and gap filling qualities of the natural insulation with the U value of the PIR. I've also looked at forgetting about using up the PIR and just going for 200mm of natural with the woodfibre board joist deepeners. Would love to hear people's words of warning on this option. Would fixing the woodfibre directly to the base of the joists be more secure? Would anyone have any thoughts on the best way to do that? Thanks in advance!