Efficiency of wood stove

[Watson]

How are wood stoves rated for efficiency? Even allowing for 10% heat loss up the chimney an 85% efficiency seems unrealistically high? Is it retained heat at a moment in time or average retained heat over time?

[CanadysPeak]

How are wood stoves rated for efficiency? Even allowing for 10% heat loss up the chimney an 85% efficiency seems unrealistically high? Is it retained heat at a moment in time or average retained heat over time?

It is meaured by dividing the total caloric energy of the fuel into the amount of energy delivered into the room. Modern designs, especially if they use a catalytic converter, can deliver 80 % , or above. Old fashioned stoves tended to run around 20 %.

I'm not sure I understand your use of "retained heat".

[Watson]

I meant retained heat as in heat retained in the room rather than up the stove pipe. The newer stoves have tube above the fire to help burn the smoke. Would this be as effective as the catylitic converter?


It just seems like the old stove really pumped the heat out, compared to the new design?

[CanadysPeak]

I meant retained heat as in heat retained in the room rather than up the stove pipe. The newer stoves have tube above the fire to help burn the smoke. Would this be as effective as the catylitic converter?


It just seems like the old stove really pumped the heat out, compared to the new design?

There is a stove design from Scandinavia which uses the heat of the fire to heat (and burn) the flue gases. I think that might be what you're asking about. They're very efficient, though I thought they also had a catalytic converter to catch what got missed. Not sure. These stoves have a low surface temperature and don't produce much radiant heat. You really have to blow the air out or, as I know one family to do, actually sit on the things.