Chimney Height question

[GunSeth]

I'm thinking about adding another three feet onto my chimney and I wanted to see what you all think.

We have a stove in the basement. Last year was our first year of wood burning. It went well although in times of high wind it was difficult to get the fire going. There was one incident with carbon monoxide when we had to evacuate the house and call the fire department. By the time they arrived the source of the CO had disappeared, however I attribute the incident to high winds in the middle of the night and low burning coals which caused some smokeback.

Below is a picture of my chimney. Would adding three feet to it help with my draft issues? I imagine that adding a few feet to the existing height could only help my situation. Thanks!

 

[Backwoods Savage]

Probably will help. You'll also need to add some supports and it could be a problem cleaning it.

 

[CrappieKeith]

Length only helps to a certain point. You are further than 10 feet to the peak and you are at least 3 feet higher than the roof line so the flue is ok.
I'd suspect that your backdrafting is due more to eithe too cool of flue or you do not have enough makeup air for the fire to burn properly.
No make air vent can cause a mini vaacume in your basement. So when winds grow it would be easy to expierence a backdraft situation.

The other thing too is that we can not see the inside of the home where the flue runs.
Too much horizontal run can also stop it drafting well.
You really should have at least 1" of rise as a minimum for every linear foot of travel on the horizontal run.

 

[CrappieKeith]

Length only helps to a certain point. You are further than 10 feet to the peak and you are at least 3 feet higher than the roof line so the flue is ok.
I'd suspect that your backdrafting is due more to eithe too cool of flue or you do not have enough makeup air for the fire to burn properly.
No make air vent can cause a mini vaacume in your basement. So when winds grow it would be easy to expierence a backdraft situation.

The other thing too is that we can not see the inside of the home where the flue runs.
Too much horizontal run can also stop it drafting well.
You really should have at least 1" of rise as a minimum for every linear foot of travel on the horizontal run.

Although from the pic your cap looks clean...if it has a screen...it can become coated and partially clogged causing a backdraft.

 

[begreen]

What else is sucking air in the basement? Is there a furnace or boiler there? Dryer, hw heater or bathroom fan?

The stack appears to have about 15' of pipe on top of I'm guessing a couple 90 degree turns. If so, the draft could be improved by another length of pipe, with a roof brace at the 5' level. Also make sure the joints and clean out cap are sealing well. If you can post an inside view of the stove and connection we can see if there is something else that could be improved. This could be something like using double-wall pipe + 2 45 elbows to connect to the thimble?

 

[Wet1]

Length only helps to a certain point. You are further than 10 feet to the peak and you are at least 3 feet higher than the roof line so the flue is ok.
I'd suspect that your backdrafting is due more to eithe too cool of flue or you do not have enough makeup air for the fire to burn properly.
No make air vent can cause a mini vaacume in your basement. So when winds grow it would be easy to expierence a backdraft situation.

The other thing too is that we can not see the inside of the home where the flue runs.
Too much horizontal run can also stop it drafting well.
You really should have at least 1" of rise as a minimum for every linear foot of travel on the horizontal run.

Uhhh? It looks a lot lower than the peak to me. Adding 3' should help the situation. I agree with the other points.

 

[DAKSY]

Looking at your pic, you are no where NEAR what code says for chimney height.
What's the roof pitch? Appears to be at least a 10/12, maybe 12/12?
Either way, code says take the top number, multiply by 10 & add 24".
So if that's a 10/12 pitch:
10 x 10 is 100 + 24 = 124" or 10' 4" from where the class A passes the roof line...
Looks like you have 6'...

 

[GunSeth]

Thanks for all the responses guys, I appreciate the help!.

Yeah, sorry for the misleading picture. The chimney is defintely not higher than the roof line. I'll try to take another pic from a better angle. I'm not sure about the roof grade but it's pretty darn steep. As of now I don't think it quite meets the 10-2-3 rule.

There is one 90 angle from the inside and probably about 3.5 feet of horizontal run between the inside and outside. I'll try to post a pic of the inside when I get home.

Unfortunetly the stove is competing with a boiler in the basement. The dryer is also down there - we try to only use it when the fire has really taken off.

 

[Wet1]

Go higher then.

Also, do you have an OAK installed on the stove? If not, it sounds like you might be a good candidate for one.

 

[CrappieKeith]

The 3.5 feet of run could be the culprit without any rise to it.

Like I was saying and I hope you understand that it could be several things not just the height of the flue.
If you do go longer I'd add an extended roof bracket(support).Anything longer than 5 feet really should have a guide on or roof bracket.
You said it's not 3 foot beyound the roof line. Since it looks like you have 3 foot sections ...you have 6 feet of pipe above your roof line.
What are the actuall dimension?
Do not confuse roof line with peak.
They are 2 seperate things.
The roof line is where the flue meets the shingles. the peak is at the very top of your house.

Let's see what your flue looks like inside the house.

 

[runandjump]

Beware! If you go higher you will need to put up guide wire/support.

 

[Michael6268]

Looking at your pic, you are no where NEAR what code says for chimney height.
What's the roof pitch? Appears to be at least a 10/12, maybe 12/12?
Either way, code says take the top number, multiply by 10 & add 24".
So if that's a 10/12 pitch:
10 x 10 is 100 + 24 = 124" or 10' 4" from where the class A passes the roof line...
Looks like you have 6'...

Im not sure I understand where you are getting these #'s. Its my understanding that most codes are 10-2-3 rule. If he is farther than 10' from where the chimney passes through the roof the the high point on the peak, theroretically he could have a 3' tall chimney from the exit of the roof. Not saying this is a good idea to have a short chimney like that but just saying if he is farther than 10 feet, that chimney is code compliant. Going up may help regardless, but there is a good chance it wont. I would wait till the burning season if possible and just rig a piece of cheap black stove pipe onto what you have, observe the burn for a while and if indeed you feel it helps then extend the class A. No sense spending time, money and making it harder to clean if your not going to benefit from it.

 

[fossil]

Looking at your pic, you are no where NEAR what code says for chimney height.
What's the roof pitch? Appears to be at least a 10/12, maybe 12/12?
Either way, code says take the top number, multiply by 10 & add 24".
So if that's a 10/12 pitch:
10 x 10 is 100 + 24 = 124" or 10' 4" from where the class A passes the roof line...
Looks like you have 6'...

Im not sure I understand where you are getting these #'s. Its my understanding that most codes are 10-2-3 rule. If he is farther than 10' from where the chimney passes through the roof the the high point on the peak, theroretically he could have a 3' tall chimney from the exit of the roof. Not saying this is a good idea to have a short chimney like that but just saying if he is farther than 10 feet, that chimney is code compliant. Going up may help regardless, but there is a good chance it wont. I would wait till the burning season if possible and just rig a piece of cheap black stove pipe onto what you have, observe the burn for a while and if indeed you feel it helps then extend the class A. No sense spending time, money and making it harder to clean if your not going to benefit from it.

If you draw yourself a little diagram, and use DAKSY's guess of 10/12 for the roof pitch, and you figure the height required to be 2' above any part of the structure within 10' horizontally of it, you'll find (with just some elementary trig or just figuring ratios), that using his shortcut thumbrule yields a number which is exactly correct. If it turns out the pitch is actually more severe (steeper) than 10/12, then the chimney's got to go even higher (and vice-versa). Forget the peak, it may or may not be the peak that's 10' horizontally from the chimney...in this case, for example, it doesn't appear to be. At some point along the vertical rise of the chimney, as the roof is "falling away" from it, that horizontal distance reaches 10'. The chimney needs to be 2' higher than that point. Rick

 

[DAKSY]

Code says that you have to be a MINIMUM of 3' out of the roof & then you have to be 2 feet higher than anything within a horizontal distance of 10 feet. Do the math. The numbers are correct. the only time they can be reduced is if you are closer to the peak.
In that instance you would multiply the top number (of the roof pitch) by the distance to the peak & then add the 24"...

 

[daryl]

10-2-3 rule If the roof pitch is 10/12 you take the pitch X 10 =100 Plus 2ft is 124 inchs. that works out to 10 ft aprox. I see only about 8 ft if those are 4 ft sections.You also should have roof brace kit on it also. Not to mention when you have that much exposed pipe the pipe is cooling your smoke that much faster.Build a chase around the pipe and you well see a huge difference. Best of luck.

 

[GunSeth]

The 3.5 feet of run could be the culprit without any rise to it.Do not confuse roof line with peak.
They are 2 seperate things.
The roof line is where the flue meets the shingles. the peak is at the very top of your house.

Let's see what your flue looks like inside the house.

Yep, I did confuse 'em. I had meant to say that the chimney's definitely not higher than the peak.

Wet1, I don't have an OAK installed but it is something that I have considered.

Here's a pic from the inside for you all to dissect. Thanks again for all your help!

 

[summit]

go higher.. you are maybe 6' from the roof to dead even w/ your cap. you will need several sections, and a couple of roof braces to make it all kosher. you probably have a natural "stack effect" anyway (where the inside of the ceilings in the tallest part of your house is taller than the chimney... add to that a basement w/out a lot of air infiltration, and a boiler and dryer vent making it worse.). go taller, and maybe add a make up air kit (there are several easy to install "passive" OAKS that don't req direct hookup to the stove.. check out condar avs 90).. these things should help you out.. And next time install the chim thru the house and out thru the roof - its cheaper and not so prone to bad draft.

 

[begreen]

Dryer next to stove is a sure sign of competition. Have you considered a clotheline in the basement for winter drying?

Add the 3ft + a roof brace at about 5ft over the gutter. Then, add the OAK. Or switch to double-wall on the inside. If double-wall, connect to the stove, with 12-18", then a 45, then a short straight connector, then another 45 into the thimble.

 

[Wood Heat Stoves]

i really dont think vertical pipe will help break his stack effect.
taller pipe wont help with all he has against him ime
draft handout explaining stack effect
(broken link removed to http://woodheatstoves.com/smoking-chimneys-draft-troubleshooting-p-12038.html)

This is especially a concern when this installation is proposed for the downstairs of a two story home. The issue is that you need "draft" for a woodstove to operate and especially to keep smoke and odors out of the home. I have attached some draft related handouts for education on this topic. The draft is strongest when a pipe vents directly thru the roof in the highest portion of the living space, looking at the whole air space as one big bubble of air pressure.

adding vertical pipe doesn't change this, but is worth a try. so is sealing air leaks upstairs!!

 

[GunSeth]

A chimney height problem no more!

 

[cmonSTART]

Great! Higher is better!

I added another 3 feet to our chimney before last winter and completely eliminated our wind issues. Being above roof line is key if possible.

 

[GunSeth]

You know, I didn't even consider this but I'll be able to put the cost of the new chimney towards the 2010 tax credit, won't I? The stove's a few years old and the chimney folks used my existing chimney pipe in the rebuild but the additional materials and labor costs can be claimed since it was necessary to bring the chimney up to code. Am I thinking clearly or crazily?

 

[leeave96]

I'm thinking an outdoor air kit would really help too.

Also, I'm just courious - how do you clean a chimney set-up like you have?

Good luck!
Bill

 

[GunSeth]

Also, I'm just courious - how do you clean a chimney set-up like you have?

I was able to clean the chimney from the bottom in the old chimney set as seen in the first pic of the thread. The chimney was going throught the window in the basement. It's now going through concrete bringing it even closer to the ground. I should still be able to access it from the bottom but it might be a little tricky.

 

[Bella77]

Length only helps to a certain point. You are further than 10 feet to the peak and you are at least 3 feet higher than the roof line so the flue is ok.
I'd suspect that your backdrafting is due more to eithe too cool of flue or you do not have enough makeup air for the fire to burn properly.
No make air vent can cause a mini vaacume in your basement. So when winds grow it would be easy to expierence a backdraft situation.

The other thing too is that we can not see the inside of the home where the flue runs.
Too much horizontal run can also stop it drafting well.
You really should have at least 1" of rise as a minimum for every linear foot of travel on the horizontal run.

I though the 10 feet was to a horizontal structure? and not the ridge.