Chimney goes all the way to the basement, wood-stove on first floor... is this a problem?

[ganesa_9]

I have a Vermont Castings Dutchwest stove tied into an existing chimney that is in the center of the house. The chimney runs all the way from the basement (used to be used for a coal furnace) and goes up to the top of the house (two stories). The wood stove is on the first floor and is about 10 feet up from the basement clean-out... chimney has a 6 inch lining all the way down to just a couple inches above the clean-out. Altogether the chimney is about 32 feet tall form basement to roof, or about 22 feet long from where the stove is tied in, up to the roof. The basement is ancient, un-insulated, cold and damp (150 year old house), and when it gets extra cold outside (and therefore cold in the basement) stove performance, including draft) tanks. As long as outside temps are in the mid teens and up everything works great... so my question is this:

Is the fact that my flue runs about 9 or 10 feet below where the stove is tied into it a bad thing? I've asked a couple professionals (local chimney pros) to look at it, and they said they've never seen anything like it and honestly don't know. I keep thinking if it gets cold enough in the basement, and with no good way to seal off the clean-out, am I getting some kind of cool air vacuum effect that's killing my updraft when it get really REALLY cold outside? If so... what could be done about it? Could I seal off the clean-out but in a way that would enable me to 'clean' out creosote and the bottom of the chimney, or should the stove be tied into the flue with some kind of elbow so that the flue ends where the stove is tied into it and seal off the clean out in the basement?

Anybody have a similar set-up?

Thanks

 

[gthomas785]

If the cleanout is open all the time as depicted, that's a problem. You should try to close it off when not actively cleaning the chimney. If it's fitted with a well-sealing door then your setup is very typical and shouldn't cause any issues.

 

[gthomas785]

You can start by just taping up a piece of sheet metal with foil tape until you come up with a permanent clean out door.

 

[ganesa_9]

You can start by just taping up a piece of sheet metal with foil tape until you come up with a permanent clean out door.

Thanks. It has one of those loose fitting cast iron doors that never actually work... I'll try your foil idea and see if it makes a difference. This only becomes an issue when the temp in the basement gets down in the 30s. I'm being generous calling it a basement, too. Only about 10 x 12, a dirt floor usually damp or wet, only accessible by outside basement doors that do a lousy job of making the basement remotely weather-tight. Like I said... 150 year old house out in the sticks.

Usually though, wouldn't a proper chimney for a wood-stove have the flue only going down to the wood-stove with maybe a little extra length for a clean-out? That way I'd only have a 24 ft chimney, which unless I'm misinformed, would be a whole lot better!

 

[begreen]

Definitely seal it off. A temporary gasket can be formed by closing the door on a thick bead of silicone adhesive sealant.

Does the chimney have a liner? Usually a 150 yr old chimney does not.

 

[gthomas785]

The chimney height is measured from the stove's flue collar up. If your clean out leg is sealed off it won't make a difference to the draft, it's like having a dead end section on an air duct. The flue cross section does matter, as begreen mentioned if it doesn't have a liner you should really get it lined. And that liner would have a tee with a cap where it meets the wall thimble.

 

[ganesa_9]

The chimney height is measured from the stove's flue collar up. If your clean out leg is sealed off it won't make a difference to the draft, it's like having a dead end section on an air duct. The flue cross section does matter, as begreen mentioned if it doesn't have a liner you should really get it lined. And that liner would have a tee with a cap where it meets the wall thimble.

It has a 6" liner as indicated in the drawing... oddly enough even though the house is very old, the chimney was added IN around 1948. It's very solid brick and has those ceramic rounded off sand colored flue liners inside the brick chimney. I had the metal flue pipe (with the TEE) added when I bought the place in 2008. I regularly sweep (myself) the flue, so it's always pretty clean... usually every two months while in use. The basement has been getting damper, even wetter, and colder the past three years as our winter routine now includes three or four nasty polar vortexes that we didn't used to get. The draft issue I've been having only started with the now regular vortex and extreme cold... it's worse during dusk and early evening, and again in the morning just before the sun comes up. Sometime around 2:30am to 3am the stove will get a wild HOT burn... all of a sudden, so I have to watch for that too. Four or five years ago this stuff never happened.

 

[NickW]

I agree with getting the bottom of the liner sealed off. The heated flue is probably drawing as much air from the open end as it is pulling air through the stove keeping the flue temperature too cool. Sealing it off should definitely improve draft and keep the pipe hotter keeping draft stronger longer.

Note that this may give you too strong of draft and a damper might be needed to control the burn based on the height on the diagram. It will also likely change your air settings on the stove.

Theoretically, say that your flue temperature is typically 350-400 degrees and sucking 1/2 of the air through the stove and 1/2 up the open end. Now you seal the open end and you no longer have cold basement air keeping the flue "cool". All air in the flue is exhaust from the stove and the flue temperature is 500, 600, 700 degrees. The hotter flue will draft stronger requiring the air control to be closed more to control the fire or even a damper added.

Absolutely do it, but be aware of what it can mean. The chimney is the "engine" that runs the whole system. Change the "engine" and it will affect the performance of the system. It may also reduce your wood consumption...

 

[begreen]

It has a 6" liner as indicated in the drawing... oddly enough even though the house is very old, the chimney was added IN around 1948. It's very solid brick and has those ceramic rounded off sand colored flue liners inside the brick chimney. I had the metal flue pipe (with the TEE) added when I bought the place in 2008. I regularly sweep (myself) the flue, so it's always pretty clean... usually every two months while in use. The basement has been getting damper, even wetter, and colder the past three years as our winter routine now includes three or four nasty polar vortexes that we didn't used to get. The draft issue I've been having only started with the now regular vortex and extreme cold... it's worse during dusk and early evening, and again in the morning just before the sun comes up. Sometime around 2:30am to 3am the stove will get a wild HOT burn... all of a sudden, so I have to watch for that too. Four or five years ago this stuff never happened.

Is the Tee capped on the bottom? If so, the cleanout seal is not important. If not, it should have been, or extended with a length terminating at the cleanout door, with a cap there. Without any cap, draft will be erratic with an leaky cleanout door below.

 

[ganesa_9]

Is the Tee capped on the bottom? If so, the cleanout seal is not important. If not, it should have been, or extended with a length terminating at the cleanout door, with a cap there. Without any cap, draft will be erratic with an leaky cleanout door below.

TEE is NOT capped at the bottom... accumulated creosote loosened during a chimney sweep falls down to the basement and can be cleaned out through the clean-out door. If it had been capped I would have indicated that in the drawing.

 

[begreen]

TEE is NOT capped at the bottom... accumulated creosote loosened during a chimney sweep falls down to the basement and can be cleaned out through the clean-out door. If it had been capped I would have indicated that in the drawing.

OK, that's can be a serious issue. Even if the clean out door is sealed, which it will need to be, some chimneys are somewhat leaky, not air tight. The proper solution is to have an extension added to the tee bottom that extends down to the cleanout door with a cap on the end or better yet with a second tee at the bottom with a cap on bottom and nose. The nose cap gets removed when cleaning.
In the short run, seal the cleanout door.

 

[ganesa_9]

I agree with getting the bottom of the liner sealed off. The heated flue is probably drawing as much air from the open end as it is pulling air through the stove keeping the flue temperature too cool. Sealing it off should definitely improve draft and keep the pipe hotter keeping draft stronger longer.

Note that this may give you too strong of draft and a damper might be needed to control the burn based on the height on the diagram. It will also likely change your air settings on the stove.

Theoretically, say that your flue temperature is typically 350-400 degrees and sucking 1/2 of the air through the stove and 1/2 up the open end. Now you seal the open end and you no longer have cold basement air keeping the flue "cool". All air in the flue is exhaust from the stove and the flue temperature is 500, 600, 700 degrees. The hotter flue will draft stronger requiring the air control to be closed more to control the fire or even a damper added.

Absolutely do it, but be aware of what it can mean. The chimney is the "engine" that runs the whole system. Change the "engine" and it will affect the performance of the system. It may also reduce your wood consumption...

I took the suggestion to 'seal off' that clean out door in the basement. I put a bead of Great Stuff around the frame of the door attached to the brickwork, then shut the door and put a bead around door. So far my stove performance appears to have doubled. I'll have to see if this will also apply once evening sets in and get the dusk drop-off in performance that has been happening. If it helps with that dusk drop-off in performance, then I think I can attribute the improved performance to sealing off that clean-out door. I only do a full sweep of the chimney once a year, and there's usually not much creosote, so it won't be too great a nuisance to pry open the door to clean out the fallen creosote. I'll use a wire wheel to clean off the old Great Stuff, and then reapply and shut the door.

 

[stoveliker]

Are you located in a valley?

Having issues at dusk could be related to inversion layers in the air (that I had develop in my previous home) at such times.
Such inversion layers can affect draft if they are low (not too high above the flue cap - don't know what is "too high" here...)

 

[NickW]

I took the suggestion to 'seal off' that clean out door in the basement. I put a bead of Great Stuff around the frame of the door attached to the brickwork, then shut the door and put a bead around door. So far my stove performance appears to have doubled. I'll have to see if this will also apply once evening sets in and get the dusk drop-off in performance that has been happening. If it helps with that dusk drop-off in performance, then I think I can attribute the improved performance to sealing off that clean-out door. I only do a full sweep of the chimney once a year, and there's usually not much creosote, so it won't be too great a nuisance to pry open the door to clean out the fallen creosote. I'll use a wire wheel to clean off the old Great Stuff, and then reapply and shut the door.

Excellent! I bet it would be even better if you can figure out some kind of cap on the liner bottom. Then you wouldn't have to mess with the Great Stuff. Maybe screw it in place or hold it up with a brick or 2 (definitely something non-combustible) so it can't fall off... Heck, a metal coffee can upside down or a metal HVAC duct cap held tight to the bottom of the liner with a brick.

 

[ganesa_9]

Are you located in a valley?

Having issues at dusk could be related to inversion layers in the air (that I had develop in my previous home) at such times.
Such inversion layers can affect draft if they are low (not too high above the flue cap - don't know what is "too high" here...)

Not in a valley in the natural sense... but my property is adjacent to a highway overpass on the east side, and has a very tall and thick windbreak of what I believe are lodge-pole pines on the west. The winds here tend to run (usually) west to east, and I really appreciate that windbreak, but I have wondered if the windbreak and the artificial ramp of the overpass also interfere with chimney function. I've considered if an inversion of air pressure or temperature could be causing the dusk drop-off, too. It also occurs to a lesser extent just before sunrise so... maybe. I'm hoping sealing off the clean-out door will also help with that. I'll see... probably tonight since it's supposed to get down to -2 degrees, and any reduction in stove performance will be felt.

 

[Highbeam]

Normally, colder outside temperatures increase draft.