Minimum chimney height

[firecracker_77]

I'm going to install a 2nd Heritage to heat a part of my space that doesn't get adequate heat in cold weather. I'm thinking the chimney will be 14 feet from top of stove to the cap. Double wall into triple wall. Is this too short to draft properly? The first Heritage has a 24 foot chimney so no drafting issues there.

 

[Backwoods Savage]

It is always difficult to know for certain about chimney height and the draw you get. We've heard of folks having well over 20' of chimney but still a poor draft. On the other hand, I am well below the recommended height and have no problem. Naturally the stove is a factor as some seem to require a bit more draft than others. As for the Heritage, I would not be afraid to run a 14' chimney with it but with more than one stove, you may want to think about an OAK.

 

[mellow]

Being a top vent stove that will help, but as Backwoods mentioned it will be hard to tell, going DW to TW will help, what is limiting you to only 14ft?

 

[Highbeam]

Read the manual. I believe it tells you the minimum stove height.

I have an all vertical, 8' of class A and then a vertical double wall telescoping section vertical to the collar, so probably under 13' of actual flue height and I would like to install a flue damper to slow it down. The heritage is not a draft sensitive stove.

 

[firecracker_77]

It's about 9 feet to the ceiling plus the Class A chimney which is probably only 5 or 6 feet. That's how I'm guessing the length. A flue damper does sound like a good idea.

 

[begreen]

I'd try it without the key damper first.

"This stove requires a minimum chimney height of 13 feet
(4 m). The maximum allowable chimney height is 30 feet
(9m)."

 

[firecracker_77]

I'd try it without the key damper first.

"This stove requires a minimum chimney height of 13 feet
(4 m). The maximum allowable chimney height is 30 feet
(9m)."

Sounds good. Maybe, I'll add an extension of Class A, but then I'd have those ugly brackets. I'll try it out first without extra pipe beyond what is required.

 

[ScotO]

I'm going to install a 2nd Heritage to heat a part of my space that doesn't get adequate heat in cold weather. I'm thinking the chimney will be 14 feet from top of stove to the cap. Double wall into triple wall. Is this too short to draft properly? The first Heritage has a 24 foot chimney so no drafting issues there.

You may want to add one more section of flue pipe. Napoleon recommends a minimum of 16' of flue, if I am not mistaken. My kitchen woodstove flue is 22' from the top of the stove to the cap, the NZ3000 fireplace flue in the living room is 16' on the nose. It doesn't hurt to have a little bit longer flue, if you can, so long as it isn't a hazard or asthetically unappealing.

 

[begreen]

If you have 14' and it is straight up off the stove I'd try it like that first. It may be fine.

 

[firecracker_77]

If you have 14' and it is straight up off the stove I'd try it like that first. It may be fine.

Thanks for all the advice. This install will be battle tested in September / October long before it's too late to make changes. I'll start with 14 feet and see how she does.

 

[Highbeam]

14' is plenty fine. Remember that these stoves are designed to burn well with the minimum chimney in a warm climate, the florida bungalow. On a non-cat, you want the minimum length required and all vertical with double wall and class A.

I brought up the damper only to point out that despite being at the minimum length, the stove still can have too much draft at times.

Of course, you always have to wonder how Hearthstone is measuring "chimney". Is that from the bottom of the firebox, flue collar, hearth level? I assumed it to be flue collar but some brands spec it differently.

I would not add anything to the chimney. Keep it at the minimum.

 

[firecracker_77]

14' is plenty fine. Remember that these stoves are designed to burn well with the minimum chimney in a warm climate, the florida bungalow. On a non-cat, you want the minimum length required and all vertical with double wall and class A.

I brought up the damper only to point out that despite being at the minimum length, the stove still can have too much draft at times.

Of course, you always have to wonder how Hearthstone is measuring "chimney". Is that from the bottom of the firebox, flue collar, hearth level? I assumed it to be flue collar but some brands spec it differently.

I would not add anything to the chimney. Keep it at the minimum.

I never had any draft problems currently and it's double wall for 10 feet and 14 feet or so of Class A. The new one will be 10 feet of double and maybe 5 or 6 of Class A. I'm so relieved to cut-down the run of Class A. That stuff is pricey

 

[Billy Sweet Chimney Sweep]

Naturally you will want to use less chimney, as it costs less. And the commenter who suggesting the installation manual is right on. After installation, if you have smoking issues, consider making the two chimneys the same height. Terminating the chimney tops at the same level can solve some smoking issues related to how your home breathes through the chimneys, and how the wind affects that. Sweeps luck to you!

 

[Backwoods Savage]

Welcome to the forum Billy.

 

[Billy Sweet Chimney Sweep]

Thanks Savage! I'm a passionate enthusiastic unabashed pyromaniac. Hope I can help!

 

[begreen]

After installation, if you have smoking issues, consider making the two chimneys the same height. Terminating the chimney tops at the same level can solve some smoking issues related to how your home breathes through the chimneys...

I'm a bit confused by this, but maybe I am misunderstanding. Terminating two chimneys at the same height is generally a bad practice. We see cases here where folks are getting counterflow with the chimney in the basement pulling smoke from the adjacent, same height chimney down into the basement.

5.17, Masonry Institute of America - "The pouring of smoke from one flue to an adjacent flue occurs where downdraft from interior suction or vertical wind currents force smoke down an inactive flue as it exhausts from the adjoing flue"
5.14, Masonry Institute of America "The top of a flue should have a height differential...as much as 12 inches to prevent smoke from pouring from one flue into the other flue"

(broken link removed)

 

[Billy Sweet Chimney Sweep]

Hey begreen, thanks for bringing this up. My advice for this thread is for two separate chimneys. We find many homes have two separate chimneys with differing heights to the top. Usually the taller of the two will dominate the available draft. The more air-tight the building envelope, the more the taller chimney will dominate. The citations above from the Masonry Institute of America look to be for separate flues in a single chimney. In that case, it is not unusual for smoke to go up one flue, and get sucked right back down the other. Usually when this happens, the flue drawing smoke right back down is providing make up air for the fireplace.

 

[begreen]

How far apart do the flues need to be before this negative effect does not happen?

 

[DAKSY]

It's about 9 feet to the ceiling plus the Class A chimney which is probably only 5 or 6 feet. That's how I'm guessing the length. A flue damper does sound like a good idea.

Don't "GUESS" the length of your chimney. Refer to the manual. Also consider the pitch of your roof & the distance from the peak to the roof penetration, to correctly establish the minimum approved height...

 

[Billy Sweet Chimney Sweep]

Hard to quantify, further apart is better, say a couple feet apart? In older homes, the flues are usually close together to reduce the number of bricks required to build the chimney. In more recent construction, it is not unusual for some large chimneys to be hollow inside. The smoke can sometimes communicate right through gaps and crevices on the inside of the chimney! And we've installed large caps to keep water out, only to find that they can make the smoke hang around under the cap and get pulled down the flue. Any combustion in a home requires a "make-up" or "combustion" air source. The need for combustion air competes with leaky drafty older homes. The need also competes with kitchen and bathroom vents! Unfortunately, while educated guesses can anticipate possible problems, trial and error seems to be the only absolute resolution. Happy fires!

 

[Highbeam]

How far apart do the flues need to be before this negative effect does not happen?

That would be the "suck radius"?

 

[begreen]

LOL, does that apply to people too?

 

[BrowningBAR]

LOL, does that apply to people too?

Yes, but that requires a flow chart, which I have miss-placed at the moment.

 

[firecracker_77]

Height differential with likely be 8 - 10 feet. Horizontal distance between 2 chimneys will be about 17 feet. Chimneys will be more or less lined up on the roof the same distance from the front of my building. The 24 footer exits at the peak and was installed in 2010. The 14 footer will be installed near the outside wall. I'm waiting till October to shell out the money for pipe and install. No sense in using cash reserves for something I can't enjoy yet. I plan on burning both full blast on cold days. At 35 degrees plus, they may be both burning but one will be allowed to cool somewhat so that I can do some cooking inside the firebox either on a grill or in a dutch oven with legs. I'm really excited about making stews and such utilizing coal placement under and perhaps on top of the dutch oven like they did back in colonial times.