Philxyz

Hello We have a small cottage in Ireland with exterior walls of old stone and 100mm EWI. This is the plan: 100mm EWI (exists) 400mm old stone wall (exists) Breathable airtight membrane against wall 20mm air gap Thermally bridged metal stud frame (with insulation) Plasterboard Does that look like a good plan? Do we need a vapour barrier? The old stone wall is sometimes exposed repointed stone, othertimes several renders. It is extremely uneven. How do we secure the stud tracks to a wall that is all over the place? Any ideas for this appreciated. I imagine an adjustable bracket hopefully providing a thermal bridge but cannot find anything. Many thanks, Phil

OK. Sorry for the delayed response, and thanks very much for the pretty unanimous and clear need to go deeper. Looks like we can get down to 180mm, will try to go deeper but wont know til on site. Will do the 2 staggered layers, foam, tape and polythene. Will look into the price for a top layer of phenolic. Thanks everyone!

We are rebuilding an old cottage and have only 120-130mm available for insulation underneath the UFH (probably in 55-65mm of liquid screed). What type of insulation, what suitable product, will give the most insulation? Thanks!