"+Kenneth Hemphill: Parker's got it right - thermal mass is a WAY bigger factor in efficiency than playing games with air.
With adequate thermal inertia, the house does not feel 'drafty' - it feels like it's a warm spring day when you wake up, and you are surprised to look out and see fresh snow on the ground outside.
Compare the heat capacity of air to earth, fireclay mortar, or brick. And consider that healthy houses ventilate about 1/3 their volume per hour. You are going to exchange some air through the building envelope - you have to to stay alive. Why breath the stale air yourself, and feed the fire fresh air? Heating with air is a highly inefficient proposition - I think the only reason we do it is it's so easy to circulate, and hard to get it 'too' hot.
You can sit on the warm bench pictured, there is no 'draft' from the windows because an updraft from the bench counteracts the adiabatic cooling, and when the fire is going the barrel radiates like a woodstove. When the fire goes out, the bench is still warm all day and night. Conventional woodstoves tend to be located in the center of a room for best effect, leaving people with their backs to the cold walls and windows. I think that, and the problem of rapid cooling as the fire goes out, are what people complain about when they say the woodstove makes the room 'drafty'. I can have the door wide open, sit on my warm bench, and be cozy.
There are safe, and unsafe, ways to add an outside air intake to one of these mass heaters if it's a concern for a particular situation. There's plenty of room along the back of the warm bench for a heat-exchanging outside air vent, but I'd open it into the room rather than the heater. Mostly it ain't broke, so 'fixing' it causes more problems than it solves."