Fireplace chimney making banging noise in wind gusts

[skyM]

Hi, all:
What might be causing chimney (metal flue) banging sounds during wind gusts? July 2020 professional install of a pre-fab wood burning fireplace (flue construction pictures are below). We had a very windy day here, and with every strong gust the chimney would make a banging sound like this (fireplace was not in use at the time - damper was closed):

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In retrospect, this was going on for some time, but I was never really able to pin-point the source until now and banging was much more muffled before. Appreciate any info. TIA!!

 

[begreen]

Is the roof accessible? If so, on a calm day go up and try to move the chimney back and forth. It looks like it is hanging in a sling made up from the straps which may be allowing movement in the offset. If that is the case I think adding a rigid brace inside of the chase may be warranted.

 

[skyM]

Is the roof accessible? If so, on a calm day go up and try to move the chimney back and forth. It looks like it is hanging in a sling made up from the straps which may be allowing movement in the offset. If that is the case I think adding a rigid brace inside of the chase may be warranted.

Thank you! The roof is not accessible to me (high slope and I don't have ladder tall enough to get up there). The original installer will be here in 2 weeks. I'm concerned about the safety. The straps themselves are there for fail-safe - they do not have any tension on them. In the high wind gusts I can hear high pitch squeaking noise coming from the cap if I'm outside, but don't see any movement.

 

[begreen]

I am not comfortable with the weight of the system sitting on offset elbows. Many chimney pipe manufacturers require bracing to support the elbows. Do you know what brand chimney was installed or what is the make and model of the fireplace?

 

[skyM]

I am not comfortable with the weight of the system sitting on offset elbows. Many chimney pipe manufacturers require bracing to support the elbows. Do you know what brand chimney was installed or what is the make and model of the fireplace?

THANK YOU!! It's a heatilator element EL42 and was put in 8 months ago by an authorized installer. The installation manual is here: https://downloads.hearthnhome.com/installManuals/4044_188.pdf Can you offer some expertise feedback if the install was done correctly?

Here are some additional photos I have. All the drywall since has been closed up of course. I have an R13 insulation in there, so I'm sure the actual sound is far louder than what I could capture on the recordings. The installer came out yesterday and put up an iPhone on a selfie stick up the flue: says that there's no pipe separations, but did tell me that at the top they put in new piping through old flue, so the space between them is what's causing it. They are coming out in 2 weeks to go up on the roof, and if that's not the problem, then drywall has to come down to open up the chase. Many concerns here at this point :/

 

[begreen]

They strapped it, which is proper, but the banging in strong winds implies movement. Roughly how tall is the chimney? Is this a one or two story setup? I'm wondering if there is a firestop at the first floor level.

 

[skyM]

Roughly how tall is the chimney? Is this a one or two story setup? I'm wondering if there is a firestop at the first floor level.

The total chimney length is about 14-15 ft. (from firebox top to the cap). I'm on the top (second) floor condo and it's going directly in the roof (I have vaulted ceiling, hence the total height). Thank you again! I'm just looking for an advice and right direction. Everything passed inspection (I did pull a permit for this).

 

[bholler]

THANK YOU!! It's a heatilator element EL42 and was put in 8 months ago by an authorized installer. The installation manual is here: https://downloads.hearthnhome.com/installManuals/4044_188.pdf Can you offer some expertise feedback if the install was done correctly?

Here are some additional photos I have. All the drywall since has been closed up of course. I have an R13 insulation in there, so I'm sure the actual sound is far louder than what I could capture on the recordings. The installer came out yesterday and put up an iPhone on a selfie stick up the flue: says that there's no pipe separations, but did tell me that at the top they put in new piping through old flue, so the space between them is what's causing it. They are coming out in 2 weeks to go up on the roof, and if that's not the problem, then drywall has to come down to open up the chase. Many concerns here at this point :/

View attachment 277498 View attachment 277499 View attachment 277500 View attachment 277501 View attachment 277502

I am not sure but it looks like there are some clearance issues with that chimney

 

[skyM]

I am not sure but it looks like there are some clearance issues with that chimney

Thank you! I looked over the installation manual, and only chimney clearance referenced there are for the header and maintaining 2" air space around it. I believe all those are met. Is this what you're referring to? Thanks in advance!

 

[bholler]

Thank you! I looked over the installation manual, and only chimney clearance referenced there are for the header and maintaining 2" air space around it. I believe all those are met. Is this what you're referring to? Thanks in advance!

The 2" is what I was referring to it doesn't look like it has 2" especially to the fiberglass

 

[skyM]

The 2" is what I was referring to it doesn't look like it has 2" especially to the fiberglass

Oh, that's just the angle of the photo that makes it seem that way... sorry, it's the only ones I got, but here's a close up. There's 2" minimum clearance there and nothing is touching the flue. Put in the fiberglass/drywall myself, total overkill on the staples - i think I put them in every 4" or so.

 

[bholler]

Oh, that's just the angle of the photo that makes it seem that way... sorry, it's the only ones I got, but here's a close up. There's 2" minimum clearance there and nothing is touching the flue. Put in the fiberglass/drywall myself, total overkill on the staples - i think I put them in every 4" or so.

Good that is why I said I wasn't sure

 

[skyM]

Good that is why I said I wasn't sure

I really do appreciate your input. Thank you. The sound frankly is just scary and it's loud. I'm not sure if this thing can hold for two weeks before they come out.

 

[gthomas785]

This is a long shot but could it be the damper flapping open and shut in the wind?

I'm asking because I have a bath fan with one of those little backdraft dampers that is constantly banging when it's windy out and the sound reminded me of that.

 

[skyM]

This is a long shot but could it be the damper flapping open and shut in the wind?

I'm asking because I have a bath fan with one of those little backdraft dampers that is constantly banging when it's windy out and the sound reminded me of that.

Thank you so much for the suggestion. It was somewhat windy yesterday, and I opened my damper. I thought perhaps wind is getting trapped in the chimney, so with that open it should not have any resistance.... Sure enough the same bang was there.

One of the examples I managed to record... (the gusts weren't even that strong):

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It is a very specific sound. Almost like a gunshot... And that's the only consistency... I'm baffled at to what might be causing it... I thought that if chimney was lose, then there would be some type of a residual rattling sound. But no. It's strong, short, loud, and occurs only with a wind gust.

 

[gthomas785]

Sounds like you have a ghost.

Where does that adjacent chimney pipe go? Basement? Is there a furnace with a baro flap that could be banging downstairs and you're hearing it through the fireplace? Grasping at straws here...

 

[gthomas785]

My only other idea, another long shot. Do you have any square / rectangular ductwork in the house? Sometimes the sides of those square ducts will deflect under pressure changes and create a banging noise. I hear it in my office building when they shut down the hvac to work on it. That could also be triggered by wind if it causes a big enough pressure differential. However, I have never known that to happen with round pipes and it seems unlikely, so it wouldn't be your chimney pipe.

 

[skyM]

Sounds like you have a ghost.

Where does that adjacent chimney pipe go? Basement? Is there a furnace with a baro flap that could be banging downstairs and you're hearing it through the fireplace? Grasping at straws here...

haha, I wish it was paranormal. then I would stop worrying about that thing coming crashing down during one of its bangs! And it would be a far cooler story to share...

The adjacent chimney is from the downstairs unit (and we all have gas boilers/water baseboard heater/through the wall ACs- no furnace/no central air/no ductwork). We're separated by a 12" slab of concrete. The banging noise is definitely isolated to my chimney. I'm 100% certain of that.

 

[gthomas785]

Well then I've got nothing. Look for any pieces with a "hinge" action that could be lifted by the wind and then dropped. That's what it sounds like to me and why I suggested the damper. Kinda like when I forget to latch my screen door before a thunderstorm..

 

[skyM]

Well then I've got nothing. Look for any pieces with a "hinge" action that could be lifted by the wind and then dropped. That's what it sounds like to me and why I suggested the damper. Kinda like when I forget to latch my screen door before a thunderstorm..

Thank you (AND EVERYONE!!) I'm sorry if it seems like I'm "shutting down" all suggestions. I'm really not.. It's just such a bizarre situation. And it's growing worse increasingly. A couple of months ago, I would hear a faint bang, and would think - oh, it's something outside getting unloaded, whatever (I am in semi-urban area). But as of a really windy day we had on 3/28 into 3/29 it's just insane!! I may just open up the drywall because honestly this is far more than just driving me nuts.

 

[gthomas785]

Nah you're fine, you're not shutting anyone down. I just hate being stumped. lol

 

[skyM]

Nah you're fine, you're not shutting anyone down. I just hate being stumped. lol

after work today I'm going out and getting a NEST cam, opening up drywall, setting it up on 24/7 record and will see if it can give me something. Seems to be the only way. Installer won't be here until the 16th, the way it's doing since yesterday (getting bangs in medium strength gusts now), I don't want to wait and see what happens.

 

[gthomas785]

I don't know if you can get close enough, but a camera outside looking at the chimney top might also give insight

 

[skyM]

I don't know if you can get close enough, but a camera outside looking at the chimney top might also give insight

When the loud banging initially occurred in 3/28 winds, I did run outside - I can see chimney/cap from my balcony. There was no visible movement , just a high pitch squeaking sound. It did not show up as anything legible on the recording, so installer just had to take my word for it.

Hey, at least this discussion is motivating me to do something instead of just waiting. Hopefully once I open up the walls I won't find any ghosts doing target practice with cannons. And if I will, then I'll happily share the NEST footage. Stay tuned.

 

[begreen]

Can you roughly determine the location of the sound? Is it up high toward the roof or down low, close to the fireplace?