You are correct. It's ~85% efficient. It burns the vast majority of the smoke so even when we're using the stove it's very rare to see smoke coming from the chimney.
It provides insulation so the coals will last longer. It also helps the fire get to a higher temperature more efficiently. 1-2" of ash is helpful. More than that and you start losing benefit, 4-5" and the stove doesn't really run as well due to poor air flow.
@@CobyElkins, happy to help. I have a whole series I've done of this stove. You should also check out hearth.com as well as the Facebook group Wood Heat. Lots of knowledge available at both of those.
