Is double wall pipe better for the fire?

CeeDee

New Member
Dec 4, 2018
32
Northern California
We currently have single wall pipe on our old stove. We're getting a new stove and will probably go with double walled pipe so we can push it closer to the wall.

To clarify, though, one store told me that single wall allows more heat to enter your home, while another store said that double wall can help with keeping the fire burning longer. Something to do with air flow, but I'm not sure.

I'm pretty sure I'm going to choose double walled, but is this true about double walled pipe? Thanks!
 

firefighterjake

Minister of Fire
Jul 22, 2008
19,052
Unity/Bangor, Maine
Not sure it would make that much of a difference in terms of keeping the fire burning longer (maybe some) . . . but double wall pipe does often mean closer clearances and they seem to last longer than single wall pipe.

Single wall pipe does tend to radiate more heat than double wall pipe . . . but me . . . I prefer to heat my home with my woodstove and not my exhaust.
 

CeeDee

New Member
Dec 4, 2018
32
Northern California
Not sure it would make that much of a difference in terms of keeping the fire burning longer (maybe some) . . . but double wall pipe does often mean closer clearances and they seem to last longer than single wall pipe.

Single wall pipe does tend to radiate more heat than double wall pipe . . . but me . . . I prefer to heat my home with my woodstove and not my exhaust.
Good point about wood stove heat versus exhaust. To have any length of pipe exposed inside the house, it'd be nice to put it to work and get some heat off of it. But the idea is for the stove to be the heat source.

Also, I think as an investment double wall makes more sense. It should last longer, and it sounds like there's a safety issue. In our smaller home it'll be nice being to move the new stove closer to the wall.
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,729
South Puget Sound, WA
The main issue besides maintaining draft is keeping creosote accumulation low. Double-wall stove pipe helps with both these concerns by keeping flue gases hotter. If one can do this with a lower fire due to double-wall pipe keeping the flue gasses hotter, then that could extend burn time. Additionally double-wall stove pipe is of superior construction having an inner stainless steel liner.
 
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Manly

Feeling the Heat
Aug 8, 2017
478
CT
We currently have single wall pipe on our old stove. We're getting a new stove and will probably go with double walled pipe so we can push it closer to the wall.

To clarify, though, one store told me that single wall allows more heat to enter your home, while another store said that double wall can help with keeping the fire burning longer. Something to do with air flow, but I'm not sure.

I'm pretty sure I'm going to choose double walled, but is this true about double walled pipe? Thanks!
I have used single wall inside, switched to double wall when we replaced the old stove with a Jotul 3cb, then after a few years switched back to a very heavy gauge single wall black with a heat shield attached to the back. This allowed us the reduced clearance and gives us a noticeable increase in radiant heat. Never had a problem with cooling flue gas temperatures. We’re in a ranch with a 4/12 pitch roof and our stack is pretty short but we get a great draft. When we had the double wall pipe I was always thinking about the wasted heat going up the stack. To each their own. Shield attached to backside of the pipe works great in our situation.
 

vwmike

Feeling the Heat
Oct 7, 2013
293
Chilliwack, BC, Can.
It was expensive but the Excel ultra black is guranteed for life, and is made in my Homeland. I like both of those things.
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,729
South Puget Sound, WA
Lots of stoves are made close by you. PE, Enviro, Regency and some BK stoves.
 
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vwmike

Feeling the Heat
Oct 7, 2013
293
Chilliwack, BC, Can.
Lots of stoves are made close by you. PE, Enviro, Regency and some BK stoves.
For sure. Until I joined Hearth.com I had no idea the PNW was such a hot bed for woodstoves! Just took it for granted growing up in a rural area, pretty much everybody had a wood stove.
 
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rtrev37

New Member
Aug 28, 2018
83
New York City
I know this is an old topic but I have a double wall stove pipe on mine because it seems I will not need the extra heat from the stove pipe. Double wall will also provide me the luxury of placing it closer to the wall which is what I need over more heat at this time. if I had a large home and needing all the heat I can get, then a stove pipe heat shield would be the better choice in giving me both clearance and the additional stove pipe heat from a single wall. So it all depends on your needs and wants.
 

UrbanBrnr

New Member
Nov 25, 2019
31
Milwaukee WI
Not sure it would make that much of a difference in terms of keeping the fire burning longer (maybe some) . . . but double wall pipe does often mean closer clearances and they seem to last longer than single wall pipe.

Single wall pipe does tend to radiate more heat than double wall pipe . . . but me . . . I prefer to heat my home with my woodstove and not my exhaust.
Could double wall pipe reduce creosote from clinging to the pipe, because the temperature would be higher?
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,729
South Puget Sound, WA
It helps reduce creosote buildup by keeping the flue gases hotter so that they exit the chimney at a temperature above the condensation point for creosote (above ~250º). Burning fully seasoned wood is the best first step toward keeping creosote accumulation down.
 
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Jackfre

Member
Oct 3, 2011
137
N CA
Back in the mid-90's Brookhaven Nat'l Labs did an analysis of venting options for oil fired equipment, boilers, furnaces, water heaters. They detailed masonry, lined and unlined, interior, ext, single wall, insulated etc in ALL configurations and lengths/heights. This study became Appendix E in the NFPA 31 Oil Installation Code. I was on that committee at the time and recall a conversation with Rich Krajewski who with John Strasser conducted the study. In our conversation Rich offered that no matter the configuration of the chimney, lined or unlined the one thing that made the most positive impact on the performance of the flue was an insulated vent connector. Now, yes we are talking wood here, but the physics are essentially the same. Hot air still rises.
I have always been of the opinion that the stove heats the place and once the heat is out of the appliance it should power an appropriate level of draft. Protecting that heat on its way up the flue keeps the flue cleaner and the stove and you happier.
 
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Highbeam

Minister of Fire
Dec 28, 2006
17,024
Mt. Rainier Foothills, WA
I have 10’ length of single wall above my nc30 noncat. The stove manual says this much is allowed. I have in IR temp gun and notice at least 100 degree drop in surface temperature from 18” above the stove to the end of the 10’ run. Yes, a lot of heat is leaving the pipe and going into the heated space but yowzers, now I need to run the stove very hot to keep the skin temperature above the 250 recommended to avoid creosote. That means running the stove in an inefficient manner. Higher air settings pushing more air through the stove often make the stove even cooler.

A double wall flue would help me run the stove more efficiently. That sweet spot with high stove temps and low flue temperatures.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,753
NE PA
Could double wall pipe reduce creosote from clinging to the pipe, because the temperature would be higher?
Yes. The object is to keep the chimney flue above 250* to the top when smoke is present. Below that temp water vapor from combustion condenses on the flue walls allowing smoke particles to stick. Excessive runs of single wall pipe allows temperature drop below this critical temperature.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,024
Mt. Rainier Foothills, WA
Yes. The object is to keep the chimney flue above 250* to the top when smoke is present. Below that temp water vapor from combustion condenses on the flue walls allowing smoke particles to stick. Excessive runs of single wall pipe allows temperature drop below this critical temperature.
Well said coaly. Can I verify that you were speaking about surface temperatures? Some folks measure flue gas temperatures with probe meters that report an internal temperature that is usually about double the surface temperature.

I can verify that single wall pipe cools the flue gasses fast!
 

Sawset

Minister of Fire
Feb 14, 2015
820
Palmyra, WI
Additionally double-wall stove pipe is of superior construction having an inner stainless steel liner.
I was on a job once, where part of the work was to replace the inside flue piping. The previous owner had used single wall, had put stress on one of the elbows while assembling (not having it turned properly, yet forcing the connection), only to later have the elbow pop open at one of the seams - with a fire going - and while they were away. There was extensive smoke damage to the house. The replacement was still single wall, yet assembled properly. Personally I would not feel comfortable having it in my house connected to my stove. I know many are. Just not here. Seems to be fairly difficult if not impossible to have a double wall elbow come apart at a seam.
 

MoDoug

Member
Feb 3, 2018
72
NE Missouri
I opted for the double wall for the reasons already mentioned. Closer clearances and hotter flue temps for less creosote build up. The thought of creosote build up and a possible burn out scares the heck out of me.
 

begreen

Mooderator
Staff member
Nov 18, 2005
81,729
South Puget Sound, WA
We have about 7' of double-wall stove pipe on our straight-up flue. The stove drafts well in milder temps and stays very clean. We have only had creosote build-up once in 14 yrs with this setup. And that was from burning maple that had gotten wet due to a leaky tarp on the stacks. Normally we get about 1/2 cup of dusty soot per year.