B-vent Efficiency

[Ehouse]

Why are b-vent stoves less efficient than direct vent and by how much, in general? Is it because using room air pulls in cold air through infiltration? Seems like this wouldn't cause that much of a difference. I would think they'd be at least as efficient as an air tight wood stove. I have a Hearthstone Sterling B-vent that needs a gas valve and am wondering if I should bother to fix it since B-vent stoves seem to get such a bad rap.

Ehouse

 

[webbie]

Using room are in this case does lower the efficiency quite a bit - especially since the flues on these are usually open all the time - that is, air moves up them constantly even when the stove is not on.
However, it would still be as efficient as most wood stoves! As an example, a good B-vent gas stove might be 60% efficient, while a top direct vent might be 75%.
Most woodstove fall in that range also.