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I've recently been looking into wood burning stoves. Many installations use a stove pipe that goes straight up through the ceiling and out the roof. Most of these use a single walled pipe for the first room (the room containing the stove), and then through the second floor and attic/roof sections a double-wall insulated pipe is used.

My question is, for what reason is a single walled pipe not used for the second floor room? Surely this would allow more of the stove pipe heat to be used to heat the upper floor? (note I mean the upper room, not the attic section).

The only possible reasons I can see are:

  • Fire hazzard. But in this case couldn't a protective guard be placed around the pipe, to stop anything touching it?

  • Increased creosote build up. But we're not talking about a massive temperature difference here - so would this really have such a bad effect?

Thanks

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I'd guess fire hazard. Around the stove, you tend to have a space without combustible materials. But in a room above, someone is liable to put their dirty clothes hamper right next to the flue pipe or try to use it to dry wet towels. –  BMitch Dec 13 '11 at 14:55
    
I'm thinking that could easily be prevented, though @BMitch. For example, via a perforated outer pipe. –  DA01 Jan 11 at 1:32
    
'doh. I need to start looking at dates more often so I'm not responding to a post from 3 years ago. :) –  DA01 Jan 11 at 1:33
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3 Answers 3

You have to use double walled pipe when going through walls and floors and what not because the double wall and the space between the pipes cools enough that it can come in contact with wall materials. Single walled pipe would get hot enough to ignite the surrounding materials.

Also, a lot of fireplace type units use a 2 walled pipe that brings in air for combustion through the outside pipe and exhausts hot air through the inside pipe, but that wouldn't be used in conjunction with single walled pipe.

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I can understand the rational when the pipe is passing though the actual floor/ceiling materials, but what about the room in between? Perhaps it's just a case of keeping things simple... –  UpTheCreek Feb 8 '12 at 7:07
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In a single story their is a giant wood stove protecting people from walking into the super hot pipe, if you continued to run the pipe through normal rooms, it would be a huge fire hazard. You'd have to maintain like 3' of clearance around it which would waste a ton of space in the rooms you'd be running it through. –  Zach Feb 8 '12 at 13:39
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The pipe on the interior of the house is called a connector. It can be double or single wall pipe. The advantages of using double-wall are closer clearances to combustibles, better drafting, and reduced creosote accumulation. As soon as the flue exits the room, be it wall or ceiling, there must be a thimble or ceiling support box that transitions from the connector pipe to either class A, high temperature pipe or a masonry chimney. The class A pipe can be double or triple wall. What is important is that it meet UL 103HT 2100°F standards. For a lot more information on this question visit www.hearth.com.

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Could you add a citation to a code requirement for this? –  Niall C. Aug 24 '13 at 15:34
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To maintain proper drafting, the flue gas must remain hot all the way up until it exits. Suck too much heat out in the upper room and you'll get not only creosote buildup, but potentially draft problems down below.

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In double-high great rooms where you often see a wood stove with a two story vent pipe, would those ever be single walled or are those likely also double walled? –  DA01 Jan 11 at 1:34
    
Those are likely single wall up to the roof line, but it can vary. –  Bryce Jan 11 at 6:44
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