Since I live in an 1880-era adobe, this is an interesting subject. You can’t just slap insulation on adobe because a moisture barrier causes condensation at the adobe/insulation interface, which over time destroys the adobe.
If fibercrete (hemp, cornstalks, whatever) is vapor-permeable but insulating it could be combined (fibercrete over adobe) to produce a combination with the insulation properties of the fiber and the thermal mass of the adobe. Which would be a serious benefit in large parts of the world.
