Thread: vent in chimney flashing?

Can anyone explain the purpose of what appears to be a vent in this chimney flashing?
Thanks

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I must have missed something in attaching the photo. Trying again.

Looks like the fresh air intake.

Should not be there.

I just ran into more or less the same thing. This fresh or combustion air intake is (poorly) mounted way up high on the flue housing of this gas log fireplace. Wouldn't the same rule apply as on a masonry chimney for a solid fuel fireplace, the intake can't be any higher than the firebox? Otherwise it's liable to think it's a chimney too. Thanks for the help!

Originally Posted by Michael Chambers

I just ran into more or less the same thing. This fresh or combustion air intake is (poorly) mounted way up high on the flue housing of this gas log fireplace. Wouldn't the same rule apply as on a masonry chimney for a solid fuel fireplace, the intake can't be any higher than the firebox? Otherwise it's liable to think it's a chimney too. Thanks for the help!

That is permitted by several manufacturers as long as the air intake is below the chimney termination. The only way to know for sure is to check the installation manual for the fireplace.

Interesting! I'll have to do some investigation along those lines. Thanks Jim!

Can you advise what brand and model this is?

Just got back in my office from inspecting this. Never seen this before and was gonna jump on the board and see if I could get some input. Lo and behold a similar thred had been started.
It seems wrong for so many reasons. I'm wondering is there any function for this?

Norm

From the look of the roofing tar, they probably had roof leaks so they cut a drain scupper into the chimney to channel the water away from the leaks!

Seriously, it appears to be a homemade attempt at makeup air. See if it doesn't dump fresh air into the home, most probably into the CAZ.

Where's a cricket when you need one? Just stupid from many angles....

Nice straight courses, too----not! I'll bet there are a LOT more goofy things with this chimney. What does it serve, other than this flood control? ;-)

Originally Posted by Bob Harper

Can you advise what brand and model this is?

Unfortunately no, I don't usually record that information. It looks like I need to start.

Originally Posted by Bob Harper

Can you advise what brand and model this is?

Originally Posted by Michael Chambers

Unfortunately no, I don't usually record that information. It looks like I need to start.

I think Bob was referring to this:

Originally Posted by Jim Brewer

That is permitted by several manufacturers ...

At least I think that is what Bob was inquiring about. Bob has seen a LOT more of those than me, but I have never seen nor heard of a flashing being approved for having ANYTHING through it (basically kills what the flashing was intended to do).

Looks like a rain water wash-out system

Many factory chimneys, whether part of a factory built wood burning fireplace listed to UL 127 or a factory chimney listed to 103HT serving a woodstove or oil flue, often state the flashing or chase cover must be ventilated. Some of these flashings comes with cooling slots right under the storm collar. If this is one of those units (OP photo), then it voids the warranty and listing as it is blocking the chase cooling system.

If the vent shown in the OP indeed serves a combustion appliance, there are several other things to note. The code prohibits the air inlet from originating above the combustion chamber. One exception might be where a mfr. has listed it for a vertical intake, such as shown but with a trap at the base just before it enters the Fp. Heatilator does this. Still, it could back syphon and cause a fire but I'm unaware of any with the trap. I have seen a vid of one with flames shooting out of the intake during wind gusts where it rose about one foot to the inlet.

Vertical air intakes would need to be firestopped and fireblocked per 602.8 in the IRC. Most AHJs want to see it transition to rigid pipe 12" either side of the firestop.

The mfr. will require the intake to commence no less than 36" below the flue gas outlet, which this possibly could violate in the OP.

Functionally, you aren't going to get squat for airflow down a 4" flex duct that far. In the first place, the actual cutout in the side of the Fp only has to be 6 sq. inches so your actual CFM delivered on a good day might be 5-10 CFM.

You can get condensation in the trap, which can grow goobers, which might not be so healthy. Maybe start a mosquitoe ranch??

If that flashing leaks, it will certainly be on the installer. This intakes are designed for vertical flat walls only. I wouldn't be surprised if there was a Fp upstairs that this intake serves. Guess we'll have to wait for the OP to check back with details.

HTH,
Bob

Michael, what you have appears to be a wood burning factory built Fp with vented see-thru gas logs.

That air intake looks like a nice water intake!

Height restriction as noted.

Sad looking logset. ST fireplaces almost always spill smoke. In this case, it would be soot and flue gases. Really bad idea. I don't know of a way to fix these Fps because air will shunt across the opening thus distorting the flames causing soot and spillage. Someone just walking by can cause this or walking into the room. Even with burner perfectly centered under chimney they tend to spill.

Is damper blocked wide open?
Gas knockout properly sealed?
Shutoff within 6 ft.?
Rating plate with listing data attached to burner?

Metalbestos UltraTemp Flashings have vents at the top, storm collar covers them to keep them from leaking

Originally Posted by Bob Boepple

Metalbestos UltraTemp Flashings have vents at the top, storm collar covers them to keep them from leaking

But not anything at all like that vent shown in the original post.

And by the size of those slots, I suspect that takes a special storm collar too.

Well, the OP has not responded since we all spent all this effort to answer his question. Unless he chimes back in, this thread is going nowhere.

Originally Posted by Bob Harper

Michael, what you have appears to be a wood burning factory built Fp with vented see-thru gas logs.

That air intake looks like a nice water intake!

Height restriction as noted.

Sad looking logset. ST fireplaces almost always spill smoke. In this case, it would be soot and flue gases. Really bad idea. I don't know of a way to fix these Fps because air will shunt across the opening thus distorting the flames causing soot and spillage. Someone just walking by can cause this or walking into the room. Even with burner perfectly centered under chimney they tend to spill.

Is damper blocked wide open?
Gas knockout properly sealed?
Shutoff within 6 ft.?
Rating plate with listing data attached to burner?

The meaning of "ST" is eluding me so far (it's late), so I can't comment on that. This fireplace was double sided, with tight fitting doors on both the great room and dining room sides. With the well fitting doors, I wouldn't think that incidental air movement would have much affect on the flame, but you may well be right. There was certainly a lot of carbon built up on the log set.

The damper was open, but not blocked open. It was equipped with a small block that kept it from closing completely, if that's what you were referring to.
The gas knockout was not observable.
Yes, the shutoff was where it should be, but no key/wrench was apparent.
As noted above, I should have looked for the rating plate, and made note of some of the information on it.

ST= See-thru fireplace

Yes, air will move right through those doors unless they are gasketed.


If the damper can close most of the way, it is wrong. The requirement for the damper clamp/ block is to maintain a PERMANENT net free opening. If the damper closes 90% then your perm. net free opening is only a few square inches. Most logsets require at least 50 sq. inches which is an 8" round Wide Open.

If you follow the gas connection, it must exit the firebox somewhere and that is your knockout.

Michael, not busting on you but if HIs get into the habit of shooting the rating plate of every appliance you inspect, it can be invaluable should you need to look it up back at the office.

HTH,
Bob

Originally Posted by Bob Harper

Well, the OP has not responded since we all spent all this effort to answer his question. Unless he chimes back in, this thread is going nowhere.

I didn't know I had to chime in to make this thread go places. I have been reading every post on this thread and learned from them. (There...I chimed in.) I have no problem at all with others posting on this thread with similar sort of situations. The vent in the picture I posted wouldn't leak but the one through the brick chimney is a different story altogether.

Bert, I guess I should have spelled myself out. Unless you can clarify the mfr. of the chimney or the appliance it serves, you cannot draw an accurate conclusion on what is going on or if this flashing must be ventilated or not. That's all.

Thanks for the chime!
Bob

Originally Posted by Bert de Haan

(There...I chimed in.)

Ding-dong goes the chime.

The vent in the picture I posted wouldn't leak ...

Why wouldn't it leak?

Looks like it could leak under the right (wrong?) conditions.

Originally Posted by Bob Harper

ST= See-thru fireplace

Yes, air will move right through those doors unless they are gasketed.

Good to know. I'll look for the gaskets on these from now on.

Originally Posted by Bob Harper

If the damper can close most of the way, it is wrong. The requirement for the damper clamp/ block is to maintain a PERMANENT net free opening. If the damper closes 90% then your perm. net free opening is only a few square inches. Most logsets require at least 50 sq. inches which is an 8" round Wide Open.

This one was wrong. It would close almost all the way.

Originally Posted by Bob Harper

If you follow the gas connection, it must exit the firebox somewhere and that is your knockout.

That much I knew. What I was trying to say was that they had that area buried with a bed of sand, and I couldn't see whether or not the hole the pipe came through was sealed properly.

Originally Posted by Bob Harper

Michael, not busting on you but if HIs get into the habit of shooting the rating plate of every appliance you inspect, it can be invaluable should you need to look it up back at the office.

No problem. That's why I come to this forum. Good common sense tips like that, and this is a good case in point where that would have been helpful.

Thanks for your input!
Mike

Hi (all) &

That's the closest thing I've seen to a roof-top water 'funnel'...

Just wait 'till the Insurance Co. gets a call (claim) for interior water-damage !


CHEERS !

Originally Posted by Glenn Duxbury

Hi (all) &

That's the closest thing I've seen to a roof-top water 'funnel'...

Just wait 'till the Insurance Co. gets a call (claim) for interior water-damage !


CHEERS !

I don't see the problem. While you have the fire going the vent on the backside of the chimney collects water. When you want the fire out pull the lever on the storage container and out the fire goes What more could you ask for.

Originally Posted by Bob Harper

Bert, I guess I should have spelled myself out. Unless you can clarify the mfr. of the chimney or the appliance it serves, you cannot draw an accurate conclusion on what is going on or if this flashing must be ventilated or not. That's all.

Thanks for the chime!
Bob

It serves a wood stove and I know that there is no fresh air coming from there to the stove. I don't know if the flashing needs to be ventilated or not but that kind of flashing usually has a loose fit at the top that is overlapped by the tight fitting flashing around the chimney so ventilation shouldn't be much of an issue. (At least that was my reasoning; hence my question about the possible purpose of this vent.) It became apparent from the replies that this setup is not very common.

Originally Posted by Jerry Peck

Why wouldn't it leak?

Looks like it could leak under the right (wrong?) conditions.

Point taken. It could leak. I was comparing this one to the one in the brick chimney. That one looks like it cannot not leak (except for under the right conditions; dry weather.)