Single wall v. double wall stove pipe

[galega]

I posted earlier about my plans for installing a woodstove in a small, uninsulated cement block cottage in a (relatively) mild climate (similar to coastal Northern California) here: https://www.hearth.com/econtent/index.php/forums/viewthread/58741/

Everyone's advice and comments were helpful in narrowing down the right size stove to look at. I'm planning on getting a Jotul F3CB (assuming they are available over in Europe, which I think they are).

This will be an interior metal chimney. I know that the metal chimney needs to be the insulated "HT/Class A" type.

Next thing I'm looking at is the stove pipe. After reading information on this site and a few other sources, it seems to me that double-wall stove pipe is the way to go: a little more expensive, but it will keep the temps higher and reduce the creosote in the stove pipe and chimney.

But I just wanted to make sure I'm not overlooking anything. Is there any reason to consider using single-wall stove pipe instead? As I understand it, besides the lower cost, single wall stove pipe would put more heat into the room. That sounds great, but I wouldn't want to do that if it was going to reduce the performance of my chimney. The winter climate is not very cold (mid 30s to low 40s most nights, rarely going below freezing) but there are prevailing westerly/northerwesterly winds blowing off the coast that I suspect will be the biggest challenge my chimney will need to overcome. Given those winds, it seems to me that keeping the chimney temps higher with double-wall stove pipe will be more important than trying to get more heat out of the stove using single wall stove pipe.

What do you guys think? Am I right to error on the side of caution and go with the double-wall stove pipe?

 

[oldspark]

I have single wall pipe but only about 4 ft of it and it works fine, how many feet of stove pipe will you need, in many cases double wall is not needed, if you have clearance problems it might be justified.

 

[Pagey]

People have nice, safe installations using both types. I used double wall to take full advantage of the Endeavor's very low clearances. Go with what fits your wallet and gives you the most peace of mind at the same time. You can't put a price on peace of mind.

 

[begreen]

Will the flue be exiting near the peak of the cathedral ceiling? If yes, use double-wall for the long, interior, connector pipe to minimize cooling of the flue gases and sustain good draft. It will only need to be class A at the cathedral ceiling support box and out above the roof for a relatively short run.

 

[backpack09]

Considering Jotul is a Swedish company, I would ASSume they are available in Europe.

 

[begreen]

I think they are a Norwegian company and yes the F3CB is sold in Portugal.
http://www.jotul.com/pt/wwwjotulpt/Main-Menu/Produtos-/Lenha/Salamandras-de-lenha-/

 

[vvvv]

prevailing wind will enhance the draft, assuming top of chimney is clear of nearby trees, buildings,etc. 2wall pipe enhances the draft also. combo of both may result in too much draft. creosote results from too much water in the wood mostly or rarely from not enough water in the wood.
detailed chimney description from top of stove to top of chimney?

 

[galega]

Will the flue be exiting near the peak of the cathedral ceiling? If yes, use double-wall for the long, interior, connector pipe to minimize cooling of the flue gases and sustain good draft. It will only need to be class A at the cathedral ceiling support box and out above the roof for a relatively short run.

It will exit near, but not at, the peak -- I'd say the length of stove pipe from the top of the stove to the ceiling will be around 15 feet. Sounds like that's toward the long end of the spectrum for stove pipe runs, and double wall will be best for keeping the stack temp up.

prevailing wind will enhance the draft, assuming top of chimney is clear of nearby trees, buildings,etc. 2wall pipe enhances the draft also. combo of both may result in too much draft. creosote results from too much water in the wood mostly or rarely from not enough water in the wood.
detailed chimney description from top of stove to top of chimney?

No trees nearby so all clear there. What would be the negative effect of having too much draft in the chimney -- faster burn time with less heat in the room?

The chimney description would be:

- stove pipe from top of stove up approx. 15 feet to ceiling
- class A through the wood ceiling, insulation, and out through the terra cotta tile roof (maybe 2 - 3 feet until exiting the roof, another approx 4-5 feet above the roof)
- I'm also thinking about putting one of these "chimney caps" around the outside of the class A chimney on the exterior, to blend in with the local architecture:

http://www.poujoulat.com/gb/par_produits_carac_tech.asp?idproduit=23

 

[begreen]

You might want to try it for a season to see how the strong winds affect operation. It could be you need a special cap to deal with that. I suspect the draft will be fine. Also, you might ask the local chimney sweeps about the wind and about birds like chimney swifts. If they are a problem in the area you may want it screened with a coarse 1.5cm screen.

 

[vvvv]

if overdrafting the stove overfires, then a damper is needed. 2wall pipe clearance is 6" , 1wall is 18"

 

[finncooker]

I have a similar set up. I like the single wall because it's cheap and clearances aren't an issue for me since my walls are non combustable stone veneer. One question I have, I get a real light dusting of black soot on my pipe and it gets all over everything. The single wall pipe is tight, but there are tiny gaps where the pipe exits my stove, Scan 5-2. Would changing to double wall eliminate this soot?

 

[begreen]

Non-combustible stone veneer doesn't reduce the clearances much unless it is installed on cement board and there is a proper ventilated air gap top and bottom.

If clearances really are ok, put some furnace or stove cement in there. Work it into the gaps well and let it set up. If the clearances are not ok, go to double-wall.

 

[galega]

if overdrafting the stove overfires, then a damper is needed. 2wall pipe clearance is 6" , 1wall is 18"

Hmmm - I guess the only way I'd know for sure if I'd be overdrafted is to try it. Clearance from the wall isn't an issue since it's non-combustible cement block. Is there a difference between vertical clearance i.e. how far below the ceiling the Class A needs to come down if I'm using single wall v. double wall stove pipe, going straight up vertically to meet the Class A?

 

[begreen]

Some stove mfgs recommend no more than 6-8' of single wall. But bringing down class A into the room is expensive and unnecessary. With a cathedral ceiling, the class A can be supported by a cathedral ceiling support box that is usually only a couple feet deep. Use connector pipe in the interior.

 

[vvvv]

if overdrafting the stove overfires, then a damper is needed. 2wall pipe clearance is 6" , 1wall is 18"

Hmmm - I guess the only way I'd know for sure if I'd be overdrafted is to try it. Clearance from the wall isn't an issue since it's non-combustible cement block. Is there a difference between vertical clearance i.e. how far below the ceiling the Class A needs to come down if I'm using single wall v. double wall stove pipe, going straight up vertically to meet the Class A?

same clearances from ceiling.

 

[vvvv]

either pipe is up to u but I'd do singlewall,ask for local advise too. @ the stove top, i'd install a fluepipe damper, above the damper I'd install a tee & then continue up. Tee above damper may help in cleaning= open teecap, place al foil on closed damper, close teecap & then brush clean the pipe- creo will land on foil, cap is removed , & creo is vacumned/removed before landing inside stove which might be a PITA to remove....good luck