Building an additional stone wall into what was a big archway and would like to insulate if I can. Old solid stone building otherwise no damp course etc. so need it to breathe. While it seems pointless as the rest of the wall is uninsulated if there’s something that could be done then its better than nothing? Id like to leave stone both in and out so it needs to be cavity or nothing. I suspect Im just going to end up making it solid but if anyone has any suggestions please let me know 🙂

Ben

Check out the Ty-Mawr website, might give you some ideas – or give them a buzz.

100mm kingspan in a cavity is what is in most modern houses

Not a cavity and kingspan….

Go to Natural Building Technologies or Green Building Store. They will sell you breathable Pavatex or heraklith. Pavatex is woodfibre rigid insulation , Heraklith is wood and wool. Both breathable, both you use a (modern, dry bagged) lime-based plaster from Baumit on existing wall, stick and screw boards on, then plaster straight on top like a plasterboard, again with a Baumit finish.

Very common on the continent (Baumit are huge), unusual in UK.

Its was my understanding that it really is pointless unless you do the whole lot. It won’t make it any warmer than it is now because the uninsulated wall will still be cold.