Thanks that's really interesting. We have stone walls that have been sand and cement rendered internally. Ideally would take back to the stone but it would be a heck of a task and have very limited budget. Diathonite purportedly can be applied to cement so hopefully we can go with that.

Did you have any difficulty convincing your builder to use diathonite? We're trying to make our very chilly kitchen a bit warmer when its re-done though our builder is only familiar with non-insulating lime plaster.