1. I haven't yet seen the Korean Ondol mentioned in this thread: https://en.m.wikipedia.org/wiki/Ondol https://en.m.wikipedia.org/wiki/Ondol 2. It would be int

1. I haven't yet seen the Korean Ondol mentioned in this thread: https://en.m.wikipedia.org/wiki/Ondol https://en.m.wikipedia.org/wiki/Ondol 2. It would be interesting to revive the old Roman hypocaust system, with the benefit of modern rocket-stove design knowledge. 3. Going the other direction, a hyper-modern system based of full gasification, followed by clean combustion of the syngas -- something that looked more like a chemical plant than an oven -- would be interesting, if maybe not actually simple/robust enough to be a good idea. Would like to see it tried though.