well 70mm ecotherm, actually (it’s all the same isn’t it?). but can I run it over the joist in the attic and then board over the top or will it crush not being fully supported?

I notice that there is a space board product which felt very similar in a hand squeeze test, but it is 3 or 4 times the price or a sheet of ecotherm.

It’s definitely not specced for this. Not good under load, I wouldn’t. Thought about Triso 10?

thanks. I wasn’t really thinking properly and lobbed a few sheets of 70mm celotex in the attic before plaster boarding the ceilings, along with some 18mm chipboard. i think I’ll lay the chipboard in key areas then the celotex and then work out how much expensive small “loft board” packs I need to cover over the celotex.