Does the cow manure really make that big a difference in durability?
Jay are you familiar with these products? I've sort of painted myself into the OPC corner and just want something that will work as good as the concrete and keep the mass in contact with the air of the living space.
And by "70mm dead air space" do you mean this gets filled with light clay straw or the studs are 70mm away from the wall and they get the light clay straw and the air space remains between the studs and the wall?
I do want a little mass to store some heat given off from the (pretty inefficient) furnace, but I don't want to answer a lot of questions from an inspector on the of chance that I opt for a more conventional replacement someday.