@nprofile1q... Moss is super. Most old log houses have it between the log beams. It lasts basically forever. After 90 years ours is brown, no longer green, but keeps on working. I've used moss again to patch any gaps.
If you apply lime mortar (or just sump lime) on top of the moss, it becomes rodent/insect proof and can handle being splashed by rain (i.e. on an exterior wall). Lime mortar works well with other open diffusion materials (wood, moss, etc).