Heat Ducting versus Stovepipe

[PhilJohnson]

Is this a wise idea? I have a whole bunch of 6 inch round galvanized duct work I have been thinking of making a chimney out of for my woodstove. I know it is only single wall so I will have it mounted about 24 inches away from the wall and the pipe will be running almost the entire length out side. Will the heating duct hold up for a winter? I don't have tons of cash for a double walled pipe but if I have to I guess I can afford some single walled stove pipe.

[uncle Will in In.]

A metal flue outside will cool off the smoke too much, and cause creosote to condense in the pipe like crazy. If you do this be sure to have a place ot the bottom of the pipe for the creosote to drain down into.

[stanb999]

In a word NO...

The reasons noted above and in addition...
The Galvanize will cook off and produce poison gas.... No galvanize inside a dwelling connected to a solid fuel appliance.
If you do this anyway it needs to be 18" from combustibles when it goes through
the wall to the outside. So you will need a whole at least 42" in diameter. Like pictured below.
Combustible wall...................Pipe....................... ............Combustible wall
framing <--------------18"-------->I 6" I<----------18"---------------------> framing

[Ross]

Bad idea duct work is 30 guage smoke pipe is 26. As mentioned the galvanizing will cook off dangerously and besides it smply won't hold up to the temp or a chimney fire.

[stranger]

real bad idea, go on craigs list and try to trade the duct pipe for stove pipe.

[Beeman]

Will it work?, yes but not long term. Is it wise?, NO definitly not.

[Hank]

Please don't do it!!!
I have seen fires started this way more than once.
There is a big differance between "heat duct pipe" and "stove pipe".
I can't stress enough, don't do it!!!

Hank
www.doublemfarmandchuckwagon.webs.com

[timfromohio]

Absolutely not!!!

Also remember there are two types of pipe you use when venting a wood burning stove. There is "stove pipe" - this is the pipe used from the appliance to whatever type of pass through you are using. A wall thimble if you're going through the wall or a ceiling support box if you going up and out. The pipe used to go from the pass-through on out that creates the chimney is "chimney pipe". NFPA 411 code dictates that this must be class A, double wall pipe. Stove pipe can be single wall or double wall, though I'd recommend double wall even for stove pipe as (1) stove will draft better, (2) it's more of a lifetime product - you'll be replacing single wall pipe, depending on how much you burn as soon as 4 or 5 years, (3) it reduces required clearances to combustibles, and (4) it's safer. Safety must be paramount in all aspects of using wood for heat. It's not worth compromising you and your family's safety.

Used pipe can often be found on craigs list like somebody pointed out. www.ventingpipe.com also has decent prices, but any double wall class A pipe is going to be costly.

Finally, install/vent the appliance according to manufacturers instructions and document the installation. For example, when I installed our new stove last year I took pics at each step of constructing the hearth to prove that what I say is under the tile top layer is really there - this was done for insurance purposes.

One last suggestion is to visit the forums over at www.hearth.com - you'll get lots of excellent advice.

[Cabin Fever]

Three is a reason why commerical stovepipe and chimney pipe is NEVER galvanized. That reason has already been presented in earlier posts....galvanized pipe gives off toxic fumes when heated to high woodburning temperatures.

[Bentley]

When a galvanized product (zinc) is heated to a certain temperature, it cooks off Phosgene gas which is deadly to humans in small quantities.
For more information, go here; http://www.anvilfire.com/iForge/tutor/safety3/index.htm

[texican]

Not a wise idea, but freezing to death isn't really a cool way of dying either (pun intended). Makes a lot of difference if it's going in a house that costs money or a deer camp thrown together. I've seen chimneys made out of metal oil can's up in Alaskan bush camps... might not be smart, but it did work.

The single wall stove pipe isn't really that much. The triple wall is wayyy high. I keep several extra sets of the single wall stuff in the barn, for future use (so if all the hardware stores shut down, I won't be bush engineering metal cans together for chimneys.

[HermitJohn]

Ok, IF you dont let it get wet, you will get by. This is THIN metal and has minimal galvanizing. Doesnt take much to let rust get start and once it does, you get holes quickly.

Saying that, regular black stove pipe though thicker has no protection at all and will rust quickly if it gets wet.

In other words none of this is good for a stand alone chimney. The galvanized will work as a liner for masonary chimney if you inspect it frequently and assuming the masonary chimney is good enough to be used without a stovepipe liner. When I lived up north, Mills Farm Fleet carried very heavy gauge galvanized stove pipe. That was good stuff and cheap. They sold it cheaper than the local hardware stores sold standard lighter guage stovepipe. As to galvanized pipe gassing, yep, it will for first four or five feet after exiting the stove where it gets the hottest. Use couple lengths of black pipe exiting stove and it wont be a problem.

My suggestion if you really need cheap chimney you either build a masonary one yourself (block with tile liner) or you go hunt down some old 6 inch cast iron sewer pipe. Its heavy to work with and still needs good clearance from combustibles but will last a good long time.

[texican]

Not a wise idea, but freezing to death isn't really a cool way of dying either (pun intended). Makes a lot of difference if it's going in a house that costs money or a deer camp thrown together. I've seen chimneys made out of metal oil can's up in Alaskan bush camps... might not be smart, but it did work.

The single wall stove pipe isn't really that much. The triple wall is wayyy high. I keep several extra sets of the single wall stuff in the barn, for future use (so if all the hardware stores shut down, I won't be bush engineering metal cans together for chimneys.

[Allen W]

Seen several made out off steel pipe.

[Sawmill Jim]

Yep and if it gets very cold and your pipe is very high when the fire burn low you in for a big surprise too .If it is real cold the pipe gets to cold for it to draw then your house fills with smoke . Don't ask how i know . Git lots of dectors .

[PhilJohnson]

Thanks for the advice everyone. I have enough stove pipe to make it to the outside and connect to the galvanized pipe. Next year I want to put in a masonry chimney but since I plan on jacking up the house and raising the foundation I didn't want to stick too much money or make something too permanent or too costly if it is just going to be replaced next year. But you all have given me some things to think about and I am going to look around and see what is for sale used.

[Alex]

Your idea is bad, dangerous, illegal, non-insurable, and a Code violation in all jurisdictions.

As mentioned in other posts, the gases generated when heating zinc galvanizing are lethal. Uninsulated pipe will condense flue gases and could cake the pipe with cresote which can ignite and burn through the light-gauge galvanized ducting.

Do not do it.

The ideas listed here are required for ANY wood stove installation, in ANY type of dwelling, no exceptions. Follow the wood stove manufacture's installation instructions exactly, along with ALL Code requirements -- NO exceptions.

We have a catalytic wood stove which seems to burn most of the creosote before it gets to the flue. And we burn full hot every so often, and have 2-1/2" high-temperature insulated double stainless steel flue.


Flue needs to extend 2' above roof or 10' from horizontal surfaces.


This package shows all the things you need to be safe.


An insulated flue, and double wall Stainless steel is a type A flue, and what is required for wood heat, we used an 8" ID flue, with 2-1/2" high temperature insulation all around.


The double wall air insulated steel flue is below the ceiling flue support thimble at the top. Our wood stove is a catalytic,as mentioned, Blaze King, 82.5% efficient (we burn 17.9% less wood, and burn-times are longer than with a standard air tight.) The side and rear clearance-reduction panels allowed us to safely install our wood stove as close as shown. Each stove manufacture lists the minimum clearances to combustibles.


Finally you need to protect the floor from all those sparks.

Alex

[PhilJohnson]

Originally Posted by Alex

Your idea is bad, dangerous, illegal, non-insurable, and a Code violation in all jurisdictions.

I won't deny it isn't a good idea but it is not illegal where I am. Dwellings built before 1980 don't have to comply with any codes in my township. Since I don't have insurance on the house that part isn't an issue. Now my neighbor to the south has run a combination of stove pipe, vent pipe, and tin cans for the past 18 years or so without trouble. Once again I am not saying this is a good plan but that is where the initial idea came from. She cleans it once a month and it seems to work well enough.

Originally Posted by Alex

Our wood stove is a catalytic,as mentioned, Blaze King, 82.5% efficient (we burn 17.9% less wood, and burn-times are longer than with a standard air tight.)

My parents use a different type of air tight stove, not a real big fan of the ones with cats because I hear they plug after a while. They have a secondary burn design which seems to be a bit easier on wood than mine and definitely keeps a fire going much longer.

[Alex]

Hi Phil,

Code reference previously mentioned is for new construction, in all Code jurisdictions, and good practice. Even though exempt if you can arrange it you might want to consider the new systems which are based on experience.

Thirty-years ago our cabin, for a few years, had a black stovepipe type flue inside the cabin, with five gallon oil buckets around the black pipe where it exited through the roof and were the flue was above the roof outside. It worked and didn't burn down our cabin. We were lucky.

Also, we didn't have the fancy Blaze King catalytic converter in the beginning, we had an Ashley with automatic thermostatic draft control. It worked fine. We feel fortunate to have the Blaze King and like it a lot.

Good Luck,
Alex