Maybe. Or in 10 years. Or next year. Possibly never. But it happens often enough that the us and Canada have written codes to avoid the issue. Also often enough that I have personally inspected atleast 10 structure fires caused by the issue.
How bad are bends in flues?
- Thread starter Hawkridge
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There might be something else inside the wall around the ceramic insert. Not sure though. Probably not, given that Japanese houses are very poorly built.
Good to know. I appreciate your input. The installers here have no idea what they are doing with this sort of thing.
Read up on pyrolysis. When wood keeps on getting heated, its ignition temperature drops. Here is an example of what was happening under a hearth pad that the owners said, "never noticed any problems with it.".
![[Hearth.com] How bad are bends in flues?](https://www.hearth.com/talk/data/attachments/298/298277-f32cc66f42eddb5ff718e70d9006c8fe.jpg?hash=5Ii-S2Tfd- "[Hearth.com] How bad are bends in flues?")
And this is an example of window trim where the stove clearances were ignored.
![[Hearth.com] How bad are bends in flues?](https://www.hearth.com/talk/data/attachments/298/298278-07d7e477579fdd5b3cef5ddc1f9671a7.jpg?hash=4HPnrDN9P3 "[Hearth.com] How bad are bends in flues?")
In both of these examples, the homeowners were not too far from having a fire break out. If that occurred while everyone was sleeping, it could have turned out very badly.
Here is a masonry chimney without proper clearances. The wood had started to smolder, but fortunately was stopped in time
![[Hearth.com] How bad are bends in flues?](https://www.hearth.com/talk/data/attachments/298/298280-730e63e04df9e7135380888dc2f7c3ec.jpg?hash=wqDWIyvZe- "[Hearth.com] How bad are bends in flues?")
And finally, here is an example where the fire finally did break out and almost took a couple lives. This was a chimney with improper clearances, connected to a woodstove.
![[Hearth.com] How bad are bends in flues?](https://www.hearth.com/talk/data/attachments/298/298279-3c5891de880df88b45f0175d5a97e962.jpg?hash=zwbWsaVsbR "[Hearth.com] How bad are bends in flues?")
And this is an example of window trim where the stove clearances were ignored.
In both of these examples, the homeowners were not too far from having a fire break out. If that occurred while everyone was sleeping, it could have turned out very badly.
Here is a masonry chimney without proper clearances. The wood had started to smolder, but fortunately was stopped in time
And finally, here is an example where the fire finally did break out and almost took a couple lives. This was a chimney with improper clearances, connected to a woodstove.
This is a classic type of cast iron stove in use in scandinavia. No longer made and obsolete. But they're not really problematic either. Based on the comments I read here, it seems creosote buildup is a huge problem for americans and they need very high flue gas temperatures to combat it.
In scandinavia various types of heaters have been used for centuries that make the flue gasses travel down various paths and also cooling it to extract additional heat. I am not sure why this is such a problem when I read american dominated forums, but it does not seem to be one in swedish or finnish forums. Is the use of green or badly seasoned firewood just that much greater, or are the heaters bad at combusting firewood properly?
As long as the dry firewood has been properly combusted, the flue gasses can safely be cooled to around 100-150 degrees celcius without running risks of condensation or creosote build up. Place a simple flue gas thermometer near the end of the chimney pipe and see what the average temperature is. Have the chimney swept every year (law here).
![[Hearth.com] How bad are bends in flues?](https://www.hearth.com/talk/attachments/1707470005378-webp.324544/ "[Hearth.com] How bad are bends in flues?")
Not relevant to the discussion of safety distances, but a lower flue gas temp would help here. We have a schiedel chimney, it's ceramic and insulated, still surrounded by rockwood insulation w here it meets the structure of the house.
In scandinavia various types of heaters have been used for centuries that make the flue gasses travel down various paths and also cooling it to extract additional heat. I am not sure why this is such a problem when I read american dominated forums, but it does not seem to be one in swedish or finnish forums. Is the use of green or badly seasoned firewood just that much greater, or are the heaters bad at combusting firewood properly?
As long as the dry firewood has been properly combusted, the flue gasses can safely be cooled to around 100-150 degrees celcius without running risks of condensation or creosote build up. Place a simple flue gas thermometer near the end of the chimney pipe and see what the average temperature is. Have the chimney swept every year (law here).
Not relevant to the discussion of safety distances, but a lower flue gas temp would help here. We have a schiedel chimney, it's ceramic and insulated, still surrounded by rockwood insulation w here it meets the structure of the house.
We are talking about the same temps. You need the exhaust gasses to stay above the condensation point 100c or 212f until they exit the chimney. If you don't do that you will end up with creosote.
And yes there are many people who still burn wood that isn't dry enough
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