Outside venting


New Member
Aug 6, 2019
I just purchased a Harmon XXV, planning to vent it through my chimney, do I need outside air or will chimney have enough draft. (1500 ft Cape, pellet stove in living room, chimney runs from basement through attic, three floors. Yes I have separate ceramic flues in chimney, one for furnace, one for stove.)


Oct 11, 2018
New Jersey
Since your pellet stove is forcefully aspirated, the draft in the chimney should not be a concern since the stove is pushing the gasses out by itself...
The Outside air is "just" a nice feature so that the stove does not pull cold air into the house to replace the air that left the house by fan through the chimney...if you have a "good" house (ach50 below 2) you should consider the outside air due to potential vacuum issues by tight house not replacing vented air fast enough...
Even i do not have such "good" house yet, i have the outside air hooked up, that that i dont have a constant air stream coming cold from other rooms towards stove...


Jan 12, 2017
I installed our XXV into existing 8" metal chimney and it runs fine without the outside air kit.
Our house is not very tight however.


Minister of Fire
May 5, 2017
Miller MO
It depends on who you ask but my professional opinion is always that it depends on how tight your house is and how high up you live. If your house is not spray foamed and is less than 1500’ ASL and your not putting it in a box basement or manufactured home, then you probably will be fine without.
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Burning Hunk
Oct 26, 2016
Metrowest MA
My house is not airtight and my stove is in the basement. One season i was not using an OAK, the second season I was venting from the chimney (the clean out and left the ash dump and damper open while using those doors closed in the fireplace). I found no difference whatsoever. I liked the idea of cycling the air in the basement, so no OAK for me.
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Reactions: Overfireinthehole
Nov 20, 2018
The stove dealer convinced me an OAK wasn't necessary. I did buy the parts (threads on here tell where to find them cheap), but the mason baulked at trying to drill through the granite wall of the chimney. I must say, we did all right last year, since the stove is near the door to the basement, but the basement did get rather cold, without the furnace running all the time to warm it up.