Question: are people making use of wood pellet stoves? I've seen those used in an apartment-style building in Italy before by plumbing the exhaust out of a window. They do need a bit of power to operate. But some are as low as 75W continuous.
Catalytic propane heaters are another option that might work well. They can be run indoors. Though they do add humidity to the air so might not be on balance a solution for mold.
Catalytic propane heaters are another option that might work well. They can be run indoors. Though they do add humidity to the air so might not be on balance a solution for mold.