Chimney Top to Reduce Blowback

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Jed1124

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I run a Vermont Castings Vigilant that I’m really happy with. I replaced all the gaskets this year but the only problem I have is on really windy days (like today) the wind shoots down the chimney and I’ll get a puff of smoke in the house, especially if the top baffle in the stove is closed and I’m not running it hard.

My question is: is there a chimney top or thimble that is designed to reduce wind flow down the chimney but allows smoke to freely escape?

I suppose a in flue damper would help, but they also reduce flue temperatures so I would like to avoid that.

Thank you for any replies and or suggestions. Hope you all had a great thanksgiving!
 
Government rules on burning wood,

The chimney should be 25% larger diameter than the stovepipe. Example, a 6” stove pipe requires a 8” chimney. For those windless nights.
 
Your comment "not running it hard" leads me to believe you may be loading or opening the stove with a relatively cold chimney.

Prior to reloading, open the bypass and open the damper all the way. Let the coals get glowing red to heat the chimney up. Draft works based on the difference between outside air and the inside air. A hot chimney will draft better than a cool chimney, relatively speaking.

Id try that before replacing the chimney cap. We live on top of a hill, for this area, and the wind is always blowing. The only time I get smoke coming back in the house, windy or not, is when I dont heat the chimney before opening the door.
 
Your comment "not running it hard" leads me to believe you may be loading or opening the stove with a relatively cold chimney.

Prior to reloading, open the bypass and open the damper all the way. Let the coals get glowing red to heat the chimney up. Draft works based on the difference between outside air and the inside air. A hot chimney will draft better than a cool chimney, relatively speaking.

Id try that before replacing the chimney cap. We live on top of a hill, for this area, and the wind is always blowing. The only time I get smoke coming back in the house, windy or not, is when I dont heat the chimney before opening the door.
Thanks Casey for your reply.
No, the stoves been running for days, wind just wipped up today and I had the problem. Your right, if I keep the stack temps high enough it’s not much of a problem, but I’ll be keeping the stove running around 700 degree’s .
I went to three stores today, and nobody had the rotating stove cap. Going to order one online.
Any suggestions of which one to get from those that are running them? They vary in price from $125-$500 plus!
Miss ya in political Casey!
 
I run a Vermont Castings Vigilant that I’m really happy with. I replaced all the gaskets this year but the only problem I have is on really windy days (like today) the wind shoots down the chimney and I’ll get a puff of smoke in the house, especially if the top baffle in the stove is closed and I’m not running it hard.

My question is: is there a chimney top or thimble that is designed to reduce wind flow down the chimney but allows smoke to freely escape?

I suppose a in flue damper would help, but they also reduce flue temperatures so I would like to avoid that.

Thank you for any replies and or suggestions. Hope you all had a great thanksgiving!
I have an insert wood stove with an 8" stainless pipe that goes inside the old 12" sqaure tile chimney, at the top of the flue is a flat plate around the 8" pipe, for a weather cap I made a 1/2" x 8" id x 4" tall steel ring and welded three legs on it and welded an 18" disc blade to the three legs about 6" up from the ring for a weather cap, works great.
 
I don't think this is a simple problem; if there's a fire in the stove and you are getting a backdraft something is amiss. The buoyancy of the hot air in the chimney should be overcoming anything trying to prevent fresh air entering the stove through the combustion air supply damper, not the reverse.

One possibility is that the house is located such that surrounding air currents in windy situations are causing a high pressure at the chimney top, like is the top of the chimney below or too close to a ridge top nearby? The chimney should be greater than 3 feet above any maximum roof height within 10 horizontal feet.

If that's satisfied is there a way that the wind can cause a negative pressure inside the house enough to overcome the buoyancy of the hot air trying to go up the chimney? Is there a fresh air supply system installed, and if so how is wind affecting it, like is it on a downwind side of the house where wind would cause it to suck? (!)

In any event it isn't one of those turbine vents you'd need for the top of the chimney, it might be a weather-vaning one--but that still is only a do-fer fix; something else is wrong. Nothing other than a rain cap should be needed for a good installation.
 
I don't think this is a simple problem; if there's a fire in the stove and you are getting a backdraft something is amiss. The buoyancy of the hot air in the chimney should be overcoming anything trying to prevent fresh air entering the stove through the combustion air supply damper, not the reverse.

One possibility is that the house is located such that surrounding air currents in windy situations are causing a high pressure at the chimney top, like is the top of the chimney below or too close to a ridge top nearby? The chimney should be greater than 3 feet above any maximum roof height within 10 horizontal feet.

If that's satisfied is there a way that the wind can cause a negative pressure inside the house enough to overcome the buoyancy of the hot air trying to go up the chimney? Is there a fresh air supply system installed, and if so how is wind affecting it, like is it on a downwind side of the house where wind would cause it to suck? (!)

In any event it isn't one of those turbine vents you'd need for the top of the chimney, it might be a weather-vaning one--but that still is only a do-fer fix; something else is wrong. Nothing other than a rain cap should be needed for a good installation.
You bring up many good points.

The chimney is about 5’ off the roof of a rear addition. Probably 18’ to 20’ off the slope (horizontally) from where the addition meets the house, but there’s probably a 20’ rise from there. That being said, we were talking about 30-50 gusts today, which is pretty out of the ordinary.

This addition is so loose (not my doing) I could not imagine fresh air supply is a problem. But I did open a window to vent the smoke and it did seem to stop so you may be on to something. I just don’t see how clapboards and pine flooring can be that tight.

After researching a bit I think I’m going to try one of those weather vane directed jobs, and I’ll let you all know how it goes.

Apart from windy conditions the stove drafts like crazy, when getting a fire going if I crack a door it sounds like a freight train.
 
Something like this might be a simple solution for your problem. I bet if under the conditions where the backdraft occurs if you try to visualize the air currents coming over that higher roof you'll 'see' what is causing it.

(Not a salesman, I just happened to do a search for what I had in mind and this site came up.)

https://luxurymetals.homestead.com/wind_directional_caps.html
 
Something like this might be a simple solution for your problem. I bet if under the conditions where the backdraft occurs if you try to visualize the air currents coming over that higher roof you'll 'see' what is causing it.

(Not a salesman, I just happened to do a search for what I had in mind and this site came up.)

https://luxurymetals.homestead.com/wind_directional_caps.html
Thanks! That is exactly what I’m looking to get.
 

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