Termination Heights of Multiple Flues in a Chase

[velvetfoot]

I'm getting a new flue installed for a wood boiler in the basement into a chase that already has flues for an oil burner and a first floor insert. When the oil flue is totally cold the draft tends to reverse and I believe some smoke comes down to smell up the basement a bit. The insert flue terminates below and upwind of the oil's, and the other cold day I could see a drifting vapor plume and how it could happen. So, I'm getting the chimney guy to try and do something about it, which I think could include the three flues terminating increasingly higher in the prevailing upwind direction. Am I on the right track. (PS: I'm still tickled that he can fit another flue in there.) I'm including a pic of what it looks like now. Wind flow is approximately from left to right. Waddya think?

 

[BoilerMan]

Generally flue reversing effect is from air leaking from your building envelope in the upper floor. This makes the house a better chimney than the chimney and creates a negative pressure in the basement and pulls down a cold flue.

Try opening a window near the oil boiler a few inches while you have a wood fire going and light a candle in front of the barometric damper of the oil. See if the flame is pulled in the direction of the chimney or the room. Close the window wait a few minutes and repeat.

You may need some make-up air in the basement and some air sealing in the attic/top floor.


TS