Have you ever considered a Rocket Mass Heater? (https://en.wikipedia.org/wiki/Rocket_mass_heater)
I've been fascinated by them since I found out about the concept but renting inside a city has never given me the chance to try one out.
We currently use a wood stove that uses a catalytic combuster, so actually reburns the smoke for even more heat. Silly efficiency and almost no particulate matter so passes even the most stringent environmental laws. Its actually one the greenest ways to heat a place like ours. (it only heats the main living area though, we use small space heaters for bedrooms downstairs)