I'll no doubt spend 15hrs over-researching this online, but as always STW is likely to point me in the right direction or give me the best solution!
I've got tongue and groove suspended timber floors and the crawl space is too low to get underneath. Last time I took a few boards up it was impossible without breaking the planks so the perfect solution of properly insulating the underside of the floor would be a hugely disruptive and difficult process. When the last occupant rewired the house it appears they made access holes with a chainsaw and pick axe!
So I've reluctantly given up on that idea and the next best thing is to get the best thermally insulated underlay. Looking in the DIY sheds the green fibreboard stuff appears to give the best U value. Tentatively considering having a layer of that plus a thinner foam underlay on top to reduce noise. But I'm just wondering if there are any products I've missed that offer a better insulation value?
The floor is already quite cold and by removing the carpet and underlay I'm probably going to struggle to equal that with laminate and underlay.
Sorry that this isn’t answering your question but thought it might be worth hearing as I suspect you’re right the insulation benefit you get from the underlay isn’t going to be all that much different from the old layers of carpet you’re taking up.
I put solid wood floor down on top of the original boards in half our ground floor about five or six years ago. I now really regret not having put the extra effort in to properly insulate (and make air tight) under there as it’s going to be so much more difficult and expensive to do now. If/when I have to do this again (hopefully moving house soon) I’ve accepted that the extra effort and cost of doing this properly is definitely going to be something we suck up when replacing flooring.
I used this
It is semi-ridged, but point loading will deform it, so you will want to cover with thin ply if you are fitting carpet. Not required if you are using laminate or LVT.
I read something on the green building forum about floating floor coverings over cellotex/kingspan type insulation. So had a go on a very small, cold kitchen floor.
I used 20 mm cellotex , 6mm ply wood then Karndean click type LVT, none of it glued. I did make sure the joints didn't coincide.
Seems ok but I only did this at the end of march, so ask me next year /in a few years time.
It's made the floor feel noticeably warmer, or is it just placebo?
