Stainless Steel for Exterior Chimney Pipes?

[kharrisma]

Hi Forum Folke,

I'm installing a woodstove to heat a room we just added to our house. The room is 250 square feet, and the stove is rate for 850 to 1600 square feet. Obviously way too much stove for the room, but I couldn't pass up the deal (half-price at a Spring sale to clear it out.) Since I'm already dealing with too much heat output, I plan on using double-walled chimney piping; DVL air-space at least, and possibly DuraTech insulated double-wall depending on feedback from you folks, to minimize heat radiated from the chimney pipe. Clearance-to-walls isn't an issue, as it's a corner installation with about 20" of stove clearance to both walls due to placement of ceiling joists... don't want to cut any of those, so moved the stove location to center the pipe exit between two joists.

I have a few questions... first, the use of air-space -vs- insulated interior piping; second, since clearance-to-combustible clearances are the same for both insulated double-wall and triple-wall pipe, is triple-walled pipe required for passing through walls or ceilings? Both are rated at 2" clearance. Third, is the use of stainless steel pipe required for exterior use by fire code, or is it just a matter of keeping the inner pipe as warm as possible to maximize draft and minimize creosote formation, as well as simple longevity in the elements?

I'm trying to keep costs to a minimum while not cutting too many corners on safety... last thing I want is a house fire, or a chimney fire! Your input is greatly appreciated!

 

[begreen]

Use the double-wall stove pipe. DuraTech is chimney pipe that is used when the pipe exits the room either through the ceiling, roof or wall.

You may be able to move the heat to the rest of the house. How is this room connected to the house? Big opening or little door? What stove make/model?

 

[kharrisma]

Use the double-wall stove pipe. DuraTech is chimney pipe that is used when the pipe exits the room either through the ceiling, roof or wall.

You may be able to move the heat to the rest of the house. How is this room connected to the house? Big opening or little door? What stove make/model?

Hi begreen,

Thanks for the reply!

I'm a little confused (probably a lot confused)... DuraBlack is the single-wall pipe, DVL is the double-wall air-space-insulated pipe, DuraTech is still double-wall but has actual insulation (refractory insulation, whatever that is precisely), and DuraTech Plus is the triple-wall with both insulation (inner space) and air-space-insulation (outer space.) Which one has to go through the structure, the triple-wall DuraTech Plus, or can you use just the DuraTech double-wall/insulated pipe?

The room is weird... had to accommodate existing structure. It's about 12' x 20', and has a single standard door off of the bedroom; this door is directly adjacent to and at ninety-degrees to another standard door that goes into the rest of the house. There is also a small double-sash window right beside and at ninety-degrees to the door (inline with that other door, as they are both on what used to be an exterior wall) that I have removed the sashes from, so it's just an opening in the wall (haven't decided how we're going to finish it yet.) I suppose one or two of those 'corner fans' that are intended to be mounted in the upper corner of a door opening would work well in that window opening.

It's a Drolet "Columbia," model DB03015. As I said, it was about $300 (half of the usual roughly $750 it sells for regularly), and has a window so we can see the actual fire, which was a must-have for me. It was also very close by, so I didn't have far to move it (HEAVY!!).

And I still don't know if the stainless-steel triple-wall is required for exterior use and/or through-structure passage, which is my biggest concern at present.

Again, thanks the reply!

 

[CenterTree]

Hi Forum Folke,

Since I'm already dealing with too much heat output, I plan on using double-walled chimney piping; DVL air-space at least, and possibly DuraTech insulated double-wall depending on feedback from you folks, to minimize heat radiated from the chimney pipe. ...

I have a few questions... first, the use of air-space -vs- insulated interior piping; second, since clearance-to-combustible clearances are the same for both insulated double-wall and triple-wall pipe, is triple-walled pipe required for passing through walls or ceilings? Both are rated at 2" clearance. Third, is the use of stainless steel pipe required for exterior use by fire code, or is it just a matter of keeping the inner pipe as warm as possible to maximize draft and minimize creosote formation, as well as simple longevity in the elements?...
!

DVL is the interior pipe you would use from stove to ceiling. (it is black).
Duratech is the Class A that goes from ceiling through roof. The DVL is air gap only.

Duratech makes Class A (exterior and passing through walls/ceilings) pipe in both Galvanized and Stainless steel. You can choose your type of metal according to your budget. Albeit, the SS will last longer. Heat is not an issue, as BOTH will suffice and be safe.

I assume you will be using 6" ID for your stove????
And I assume you are going straight up through the ceiling??

As far as double or triple-wall class A, that depends on brand really. But, it seems like you "might" do better with the double wall (in Class A) as it is easier to get between the joist/rafter if you set the stove just right. Double wall Class A has an exterior diameter of 8". While triple-wall pipe would be 10" and would be real close to the joists if they are 16" OC. Still doable though.

Duraplus is the triple wall stuff.

 

[CenterTree]

Hi begreen,

Which one has to go through the structure, the triple-wall DuraTech Plus, or can you use just the DuraTech double-wall/insulated pipe?


And I still don't know if the stainless-steel triple-wall is required for exterior use and/or through-structure passage, which is my biggest concern at present.

Again, thanks the reply!

The triple wall is NOT "required" , unless you live in a trailer (mobile home). You can use it if you want though.

And, YES, the Stainless (shiny stuff) or galvanized is needed to pass through structure. Never use BLACK pipe to pass through walls/ceilings.
Bgreen will set you straight...LOL.

 

[kennyp2339]

The room is weird... had to accommodate existing structure. It's about 12' x 20', and has a single standard door off of the bedroom; this door is directly adjacent to and at ninety-degrees to another standard door that goes into the rest of the house. There is also a small double-sash window right beside and at ninety-degrees to the door (inline with that other door, as they are both on what used to be an exterior wall) that I have removed the sashes from, so it's just an opening in the wall (haven't decided how we're going to finish it yet.) I suppose one or two of those 'corner fans' that are intended to be mounted in the upper corner of a door opening would work well in that window opening.

That room sounds comfy, get a few recliners and enjoy staying warm when its a blizzard outside.

 

[begreen]

Duratech makes Class A (exterior and passing through walls/ceilings) pipe in both Galvanized and Stainless steel. You can choose your type of metal according to your budget. Albeit, the SS will last longer. Heat is not an issue, as BOTH will suffice and be safe.

DuraVent is the manufacturer. They make two types of chimney pipe - DuraTech and DuraPlus. DuraTech is double-wall chimney pipe, DuraPlus is triple-wall chimney pipe. DuraTech is their premium line of chimney pipe, DuraPlus is the economy line.

 

[Highbeam]

I too use and prefer the double wall insulated class A duratech instead of the triple wall air cooled duraplus for all of the class A needs. The duraplus is really big, and being air cooled it doesn't warm up as well as insulated duratech pipe. Might be slightly cheaper.

 

[bholler]

The triple wall is NOT "required" , unless you live in a trailer (mobile home). You can use it if you want though.

And, YES, the Stainless (shiny stuff) or galvanized is needed to pass through structure. Never use BLACK pipe to pass through walls/ceilings.
Bgreen will set you straight...LOL.

Triple wall is not required in mobile home applications either. The triplevwall option is a cheaper pipe because it uses half the expensive insulation that the doublewall uses. Yes it is still safe but it is an inferior product

 

[kharrisma]

Pardon... I seem to have created some confusion here. The following is taken directly from DuraVent's "All Products" catalog (paraphrased):

DuraBlack is single-walled "black stove pipe." Plain steel or stainless. Clearance to combustibles is 18". OD is very close to 6".

DVL is double-walled with air-space insulation. Clearance to combustibles is 6" to walls, 8" to ceilings. Inner wall is stainless, outer wall is black-painted galvanized steel. Pipe walls are overall 1" thick, so a 6" ID pipe would have an 8" OD.

DuraTech is double-walled with refractory insulation. Clearance to combustibles is 2". Inner wall is stainless. Outer wall comes in stainless, galvanized, and a few sizes are black-painted galvanized. Pipe walls are overall 1" thick, so 6" ID = 8" OD.

DuraTech Premium is double-walled with mineral fiber insulation. Clearance to combustibles is 2". Construction is stainless steel inside and out. Wall thickness is not specifically stated, but in the general description heading this section, it states 2" thick walls, so a 6" ID pipe would have a 10" OD.

DuraPlus is triple-walled, with refractory insulation in the inner space, and air-space insulation in the outer space. Clearance to combustibles is 2". Inner wall is stainless. Middle wall is aluminized steel. Outer wall is either galvanized or stainless. Pipe walls are overall 2" thick, so again, a 6" ID pipe would have an OD of 10".

So, DVL would be "bottom tier," cheapest way out other than DuraBlack single-wall pipe; OD is 8". Next up would be the DuraTech with refractory insulation; same OD as DVL. Next up from that would be DuraTech Premium with better insulation and thicker walls (2", so a 6" ID would have a 10" OD.) Finally, the DuraPlus triple-walled pipe would be "top tier," with it's inner insulating layer and outer air layer. A 6" ID pipe would have a 10" OD. All have 2" clearance to combustibles, except DVL which is 6" or 8".

DVL ( or DuraTech) would be interior only, up to the ceiling support box but no further. Where I get confused is which pipe can be used to pass through the house structure (wall or ceiling.) I get the impression that triple-wall stuff (DuraPlus) has to be used from the ceiling support box up through the roof, though with it's clearance to combustibles being the same as everything else except DVL, I don't really see why. Mainly, I want to be sure that the triple-wall stainless isn't required for outside use as well as for through-structure (if that's even a requirement.)

 

[begreen]

DuraTech Premium is a new line. There's also DuraTech Canada now. Looks like I need to update my catalog. 6" DVL has an OD of 7".

Stove pipe, whether single or double-wall is only for use within the room envelope. Chimney pipe must be used when passing through a wall or ceiling. There is no need or use for triple-wall chimney pipe if one is using DuraTech.

 

[Highbeam]

Stove pipe, whether single or double-wall is only for use within the room envelope. Chimney pipe must be used when passing through a wall or ceiling.

Allow me to add that once you switch to class A chimney pipe you can't switch back to interior stove pipe. So it's class A from the first wall or ceiling penetration to the cap. Yes, it can be expensive if you have a long chimney run.

 

[kharrisma]

DuraTech Premium is a new line. There's also DuraTech Canada now. Looks like I need to update my catalog. 6" DVL has an OD of 7".

Stove pipe, whether single or double-wall is only for use within the room envelope. Chimney pipe must be used when passing through a wall or ceiling. There is no need or use for triple-wall chimney pipe if one is using DuraTech.

Ah.... so the insulating air space of DVL pipe is only 1/2" thick; I missed that little detail. Thanks for the heads-up.

I also hadn't caught the differentiation between "stove pipe" and "chimney pipe." I thought single-walled pipe (DuraBlack or equivalent) was "stove pipe," and all the other multi-walled stuff was "chimney pipe." So when does 'stove pipe' become 'chimney pipe'?

It would be nice if I could find a site that explained all these generalities without getting into specifics of the particular product. The manufacturers are great at describing their various products... but not so great at things like application, such as which products cannot be used in this location but are fine for that location (as in the "stove pipe within the room envdelope only" mentioned above. Or differentiating between 'stove pipe' and 'chimney pipe.' Perhaps experienced installers can read between the lines, or apply their knowledge of various codes to figure all this out, but the average (or even smarter than average) DIY'er is going to have a hard time figuring this out.

 

[kharrisma]

Allow me to add that once you switch to class A chimney pipe you can't switch back to interior stove pipe. So it's class A from the first wall or ceiling penetration to the cap. Yes, it can be expensive if you have a long chimney run.

Ah, thanks... that was another question I hadn't asked yet; can't pull a "triple-wall-through-the-roof" then switch to double-walled/insulated for above the roof. Good to know. Wonder why, though? Differing OD's maybe, water leakage into the pipe interior?

I'm lucky in that it's only a seven-foot run to the ceiling. Being a cathedral ceiling, and a thin one at that ("cold roof"... boards, foam, foam, sheathing, metal), only about six inches, adds almost nothing to the run, and from the roofing, I have to go up another five feet two inches to achieve the "two feet taller than the nearest roof within ten feet," so I'm calling it six and a half feet. It'll need a brace, of course. And in my case, where the pitch is only a 3:12, the snow tends to pile up and creep downwards like a glacier, so a snow-splitter is probably in order as well. This same problem did quite a job on a plumbing vent stack sticking through the roof (it used to run along an outside wall, and terminated right below the roof overhang... after adding the room, it had to be extended and run through the roof, with a chase box inside. Looks better than it sounds... it's near a corner so I added small shelves between it and the corner; looks almost like it was designed that way, rather than being a matter of necessity.

 

[begreen]

This info is in many stove manuals and stove hookup instructions published by the pipe manufacturers. SBI (Drolet, Osburn) does a pretty good job on documentation. Also, download the Duratech and DVL installation guides for example. There is this article too:
https://www.hearth.com/talk/threads/the-basics-on-how-to-install-a-wood-burning-stove.147798/

 

[Highbeam]

Ah, thanks... that was another question I hadn't asked yet; can't pull a "triple-wall-through-the-roof" then switch to double-walled/insulated for above the roof. Good to know. Wonder why, though? Differing OD's maybe, water leakage into the pipe interior?

I'm lucky in that it's only a seven-foot run to the ceiling. Being a cathedral ceiling, and a thin one at that ("cold roof"... boards, foam, foam, sheathing, metal), only about six inches, adds almost nothing to the run, and from the roofing, I have to go up another five feet two inches to achieve the "two feet taller than the nearest roof within ten feet," so I'm calling it six and a half feet. It'll need a brace, of course. And in my case, where the pitch is only a 3:12, the snow tends to pile up and creep downwards like a glacier, so a snow-splitter is probably in order as well. This same problem did quite a job on a plumbing vent stack sticking through the roof (it used to run along an outside wall, and terminated right below the roof overhang... after adding the room, it had to be extended and run through the roof, with a chase box inside. Looks better than it sounds... it's near a corner so I added small shelves between it and the corner; looks almost like it was designed that way, rather than being a matter of necessity.

That will be a pretty easy job then. 7 feet of dvl inside and then another 7 feet of class a from there. If I were you I would use 8’ of class a which still only requires one brace but gives you 15’ of flue which is a common minimum.

Hopefully it’s all vertical which makes it draft better and easier to clean.