What height should double wall instead of single wall pipe be used?

[Mr_Super-Hunky]

Well the time has finally come to install my new wood stove; (We were waiting on our final home inspection and had to finish a few things).

I talked to a few local stove shops to give me a bid on installing the stove (and piping) and I am getting very mixed opinions on what type of pipe to use. Some guys say to only use double wall pipe as the height of the piping is 25' and the double wall pipe is needed to maintain the heat all the way up the pipe (thereby keeping the gases from depositing creosote on the pipe if cooled down). Thgis makes perfect sense to me.

A couple of other stove installers suggested that I only go with a single wall pipe as I would be loosing out on all the radiant heat of 25' of piping. They further went on to say that the double wall pipe (as stated above) sounds good in "theory", however, they claim that they see almost zero difference in soot buildup after a year in a single wall vs double wall pipe. They say that after a year, both pipes will need to be swept irregardless of single or double wall and the extra amount of soot buildup in the single wall is very insignificant. They say, those who spend the extra money on double wall pipe are just wasting their money. Again, they say "in theory", the double wall pipe sounds good, but after literally several hundred (or more) sweeping jobs, in "reality", the singlw wall is almost as good, a lot cheaper, you get much more radiant heat from the pipe, and you need to sweep the pipe after a year anyway!.

Now, please realize this is only what installers are telling me. A few of them actually. I don't want to create a fire hazard or anything but now I am not sure what to do; especially that a few of my neighbors have wood stoves with fairly high ridge lines like mine, all using single wall pipe for years now.!!

Your thoughts?

 

[builderbob]

The 25' of pipe you mention---how much of that is inside the heated envelope of you home, and how much is in the attic and above the roof.

Seems like attic and above roof is where you would want the double wall to keep that part of flue warm to reduce creosote buildup.

But inside, in the heated envelope of your house, perhaps there the single wall makes as much sense, and is a bunch cheaper.

Those would be my "theories".

BTB

 

[Mr_Super-Hunky]

BTB:

What you are saying is something I forgot to mention. The stove installers that say to use single wall pipe also said that due to your ceiling height, most of the warm air in the house will be up high anyway keeping the pipe itself nice and warm. I did leave out that they suggested to use 4' of double wall pipe (simpson duratech) on the outside of the house connected to the black "box" mounted in the built up roof and to use 21' of single wall pipe on the inside of the home up to the black box.

 

[webbie]

In general, I would say 10-12 feet of single wall is the max - and I would definitely spring for the welded 22 gauge (not snap lock).

If you have a sloped ceiling type of installation, you can usually hang the insulated class A chimney a certain number of feet below the ceiling.

Considering an efficiency stove and 10 feet of single wall pipe, I think it is a point of diminished returns in terms of extra heat from the pipe above that. I would agree with the sweeps that creosote is unlikely to be a problem given your newer stove and a straight up situation. But I still would hardly trust a 20 foot run of single wall.

And did you mean that 4 feet is the TOTAL length of double class A the system would us?

 

[begreen]

The idea that 90 degree ceiling ambient vs 70 at floor level is going to make a difference to the interior gases in the pipe is pure BS. And don't forget the ceiling fans will be working to even out that stratification. On the exterior, it has to be class A pipe. That is different from the interior double wall pipe (Duravent DVL). Personally, on the interior I'd go double-wall all the way, but it's your call.

 

[jtp10181]

We always install double wall. Don't even offer single wall unless a customer asks about it.

 

[elkimmeg]

Most stove manufactures state the max length of single wall pipe run I read you manual for their recomendations, but they did not make any.

All answers you got are true to an extent. Web had it best 10' is a norm length for single wall pipe. Be green is right about anbience temps.

Jp advice on using only double wall again a good solution..

your installers are also correct simgle wall pipe will radiate more heat to the living space but heat is also needed for smoke to rise if too much heat is lost it will not draft as well and cresote accumulates at lower stack temps.

Web hit another important connector pipe should be the shortest straightest possible length It soulds like you chimney is better than 2/3 connector pipe.. Your chimney really does not start till you enter the class A pipe. Even double wall connector pipe is just that, connector pipe. ITS the chimney part that is tested for safety not connector pipe. I would be thinking about more
class A pipe to reduce connector lengths ..Naturally double wall offers less heat dissipation but better drafting and you are talking a considerable connector run.

Then there are the use of combinations single to double to class A or more class A and less single

Again I agree with WEB 22 gage welded seams pipe is far superior that common 24 snap fit smoke pipe.

Actually all advice is ok its like shopping at sears good, better, and best. Naturally as you improve the installation it cost more. The object it to get it into the class A as soon as possible

 

[Bill]

I have an open ceiling to the second floor, I installed the double wall pipe mostly for safety. I just had more confidence in stainless. Also my pipe has slotted vents to allow a small amount of air to pass between the layers. The black exterior of the pipe is nicer looking than my previous install. I also believe I have better draw, the only difference between the two different stoves I had was the double wall interior pipe. I also have plenty of heat from my stove. The pipe does give off some heat to the room, but I haven't put a magnetic thermometer on the pipe to check temperatures, I use an internal thermometer. But this heating season I will check. It cost a considerable amount of money to upgrade to the better pipe but I have no regrets.