This would be on the leeward side of the house, so I'm sure soot, but maybe it would work okay.
I have two metal chimneys in a chase. One is for the insert on the first floor and has a 6" liner. The other is for the oil boiler. It's Metalbestos of some type, if the literature left behind by previous owner is correct-6" flue on the boiler -assume the flue is 6".
I wonder what the liklihood is I could use that existing oil burner flue anyway. Like I said, the house is 10 years old but the boiler didn't see much use for 6 years or so. There MIGHT be more room for another flue in the chase. It'd involve, I imagine, taking off the chase siding and some, if not all, the sheathing, creating a new chimney cap.
Currently there is a little smokey smell down in the basement from downdraft through the mostly unused oil chimney. I guess a power venter could help with this since the wood boiler would be hot all winter.
Or, I could do a direct vent pellet boiler. More convenient, possible direct vent, more operating cost, less or possibly no storage. But...I have about 35 stacked cords in the yard.
While I have the fever, which for me, historically, is very dangerous, deep down I don't want to do something really dumb. It would be nice to have a more even heat. My plan is to head over to AHONA this morning if he's open (2 hr. drive). I'm sure that'll fan the fever.