Efficiency Direct Vent vs B-Vent
We're getting ready to install a pellet stove. It can be either installed with b-vent or direct vent. If b-vent, we'd let combustion air come in through the back and ulimately, from outside. Our house is about 10 years old but by no means anything near airtight. Even our whole house fan grill would provide enough combustion through put and along with all the imperfectly sealed doors and such, it would more than suffice.
However, it occurs to me that direct vent, on a sufficiently long enough run, will be much more efficient because the air coming in will scrub almost all the heat exiting outside and will result in a much less heat loss to the outside. Since I have to get cold air from outside either through imperfectly insulated parts of the house or through a single pipe that that encases a smaller hot exhuast pipe, it seems like a no brainer.