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Wind Noise in Chimney Liner

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Willhound, Apr 25, 2006.

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  1. Willhound

    Willhound Feeling the Heat

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    Well the snow is now mostly gone, and things have warmed up to the point that I've had about a week without having to burn the Summit. Tried a few times at night because I just like looking at it so much, but ended up having to open all the windows....

    Anyway, since I haven't been burning, and it's been windy here the last few days, I'm getting a deep resonant whistling noise as the wind blows across the top of my S.S. liner, just like blowing across the top of a pop bottle. Driving the wife crazy, makes the dog howl, and everybody's looking at me to do something.

    When we installed the liner last fall, it worked out that there was about 16" sticking up above the flue collar. It was dark and cold by then, so I agreed with the installer that we should leave it long and try it for the winter. He agreed to come back this spring if I wanted him to shorten it a bit. Apart from looking a little odd sticking up so far, I figured it might help with additional draw. Now I'm wondering if this is what is contributing to the whistling noise?

    I've also tried different damper settings to see if this helps, but it doesn't. Leaving the door open does, but obviously not a full time solution. I also thought about stuffing something into the pipe, but I'm afraid of forgetting about it when I go to light up the next time. Because leaving the door open helps, it makes me think that the wind passing over the top of the liner is causing a venturi effect that is sucking air up the chimney, and the whisling is actually air passing through my air inlets?

    Any thoughts, or anybody else ever experience this?

    Willhound

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  2. Shane

    Shane Minister of Fire

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    Very well could be. You should first try shortening it. IF that doesn't work then your only option is to leave the door open or to not forget that you stuffed something up in there. Even with the chimney stuffed you may have wind noise still.
  3. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    If you do end up stuffing something in it do like they do with aircraft engines. Tie a long red or yellow strip of fabric onto the top of the chimney to remind you. Lay one in the floor of the stove too so if you go to put kindling in you will go "Oh s***!" and take a trip up top.
  4. wg_bent

    wg_bent Minister of Fire

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    I'm sorry Will, but I only got as far as "dog howl" and started LMAO. Can you put a damper at the top?
  5. Willhound

    Willhound Feeling the Heat

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    Pretty good suggestions so far, thanks. I guess my first step is to get the installer back here and get his opinion. I want to stay away from any solutions that require getting up and down on the roof, only because I know there will be plenty of opportunities to use the insert between now and next fall, so I want to stay ready. (It snowed here last July).
    I'll also look into Dylan's pipe damper idea as it had occurred to me also, but I'm pretty sure that local code doesn't agree.

    Maybe shortening the liner, and perhaps a different cap might do it.

    Willhound
  6. webbie

    webbie Seasoned Moderator Staff Member

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    I think changing the type of cap on the top might fix this.

    Of course, you could make it look good by using a Proper Topper.
  7. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    But when you put a Proper Topper on it then the wind will play Barry Manilow tunes and the dog will go bananas.
  8. Shane

    Shane Minister of Fire

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    I've had limited to no success with reducing chimney wind noise with different styles of cap. Of course you can prevent wind related downdrafts with different styles but I haven't been able to muffle the noise enough for alot of customers. One thing I did with a ZC gas fireplace once is built a chase and horizontally terminated the vent on the least windy side of the chase this worked well. Ocassionally I can get a slight reduction in noise with different styles of cap but rarely am I able to completely solve the problem. Of course we're a little different here in Wyoming as a 30mph wind is a breeze. What types/styles of caps have you had the best luck eliminating wind noise with Craig?
  9. thechimneysweep

    thechimneysweep Minister of Fire

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    Hey Willhound,

    The phenomenon you're describing sounds like one we've always referred to as "Coke Bottle Effect". The wind blows across the top of the liner, catches on the back edge, and flows down the backside of the flue. When it hits the bottom of the stove it rolls back up the front side of the flue, and the friction of the downward-flowing column against the upward-flowing column makes the noise. Two things we've found to work: bust the bottom out of the Coke bottle (like you're doing when you open the door of the stove), or divert the flow of air across the top. Both Metalbestos and Duratech incorporate bands of metal around the cap to solve this problem. The Vacu Stack cap seems to work as well, but also increases updraft whenever the wind is blowing, so it can affect the rate of burn in windy conditions.
  10. Willhound

    Willhound Feeling the Heat

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    Thanks again for the info guys. Wouldn't be so bad if it was just wind noise. I used to get that all the time with my open masonry chimney, but this is a constant (when the wind blows) deep whistle, more like the "coke bottle effect" that Tom mentions. I was going up top for a spring liner cleaning this weekend anyway, so while there, might look at either shortening the liner, or replacing the cap. I'll let you know.

    Willhound
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