Stove Pipes.. design vs function. How much is too much?

AdironDoc · May 10, 2011, 07:43:18 AM

As my design shapes up, I've not yet come to a conclusion about my woodstove. It will be in the center of the far wall so that when being used, it will serve as the center of attention with visible flames. As the wall is 24 ft high in this cathedral area, it makes me wonder about the length of pipe. Drawing heat as the fumes rise will be a nice benefit to going higher, but I can't help but feel a small stove with huge length of pipe will appear odd. Anyone have experience in this or care to share with me how theirs turned out? I will make an apron and backing from manufactured stone board. Thanks

Doc

Squirl · May 10, 2011, 09:07:15 AM

This seems like an esthetic opinion question more than function so I will preface this with these are just my two pennies worth. I recently got a book "The Cabin" by Mulfinger and Davis. They have hundreds of pictures of cabins with wood stoves and fireplaces. I found it to be a very inspirational book. The book has probably a half of a dozen or more cabins with cathedral ceilings with long stove pipes. They don't look any different than the ones with short pipes in my opinion. I notice a difference in looks more from the girth of the pipe in relation to the size of the stove or surrounding cabin. I notice the stove pipe on the jotul whether the pipe is short or long.

May 10, 2011, 09:32:24 AM

It's more than simple aesthetics. There is some science behind it.

Before deciding on the pipe length I believe you need to decide on the make and model of the stove. Then you read the owners / installation manual to see what restrictions on pipe the manufacture has. For example, my Vermont Castings Aspen has a maximum black pipe length of 8 feet and a minimum overall length of 16 feet from stove to chimney cap. Some stoves can be used with two doameters of pipe, 6 " or 8" for example. However, in the case I vaguely remember (no name), only one of the two sizes was recommended for use with the doors open (as a fireplace).

If you attempt to draw too much heat from the long length of black single wall pipe the gases in the flue can cool to where creosote formation occurs readily. Cooling the gases also slows their upward flow reducing draft.

Also follow stove mfg's clearances as minimums. More never hurts as far as safety goes.

JRR · May 10, 2011, 10:20:10 AM

I haven't install a stove and piping system yet ... but it's on "my list". As Don mentions, the exhaust gas can be expected to cool and contract as all combustion completes and the hot air continues to rise. I haven't done the math or the investigation .... but I would expect, on a tall flue system, there may be benefits in stepping the flue pipe down in diameter to try to keep the velocity from slowing too much. A long inverted cone might be ideal ... also difficult to fabricate. But I'm guessing away here ... no experience whatsoever!

SkagitDrifter · May 10, 2011, 10:22:35 AM

Hey Doc-
I had the same thoughts when placing my wood stove- I wanted the stove to be the focal point of the room but more importantly I wanted the stack to be as close to the peak on the outside- snow sliding down the metal can tear the pipe right off the roof in our area. Also, I kind of painted myself into a corner and was forced to run the pipe partly in front of the gable window.
I used double wall pipe so the draft is is never a problem - even on the coldest days.
As you can see from the pictures the black pipe is quite tall- 18' where it hits the flat part of the ceiling. Building a chase is an option for you but for me the pipe adds a rustic feel to the place. When it was all said and done I never thought about it again after lighting that first fire on a chilly fall evening.
Good luck and all the best-
Tom
http://countryplans.com/smf/index.php?topic=5327.20

May 10, 2011, 10:47:49 AM

Thanks guys! I will look at Napoleon's installation manual for the Timberwolf to see the maximum length. Will a double walled pipe reduce the heat that radiates into the living space?

Tom, your stove looks great and was exactly the kind of example I was looking for. I think you're also right that after it's there, I'll not pay it any mind from that point on. Anyway, luck was on my side as my stove arrived with broken glass. I asked that it be replaced. They did and never asked for the first one back (too costly to ship damaged junk back I'd imagine). Amazingly, they sent a third at the same time. I asked them to take it back any number of times but never heard back from them. It's been 8 months. Looks like I got three stoves now. Go figure. That's a good reason to build another cabin!

Quote from: SkagitDrifter on May 10, 2011, 10:22:35 AM
Hey Doc-
I had the same thoughts when placing my wood stove- I wanted the stove to be the focal point of the room but more importantly I wanted the stack to be as close to the peak on the outside- snow sliding down the metal can tear the pipe right off the roof in our area. Also, I kind of painted myself into a corner and was forced to run the pipe partly in front of the gable window.
I used double wall pipe so the draft is is never a problem - even on the coldest days.
As you can see from the pictures the black pipe is quite tall- 18' where it hits the flat part of the ceiling. Building a chase is an option for you but for me the pipe adds a rustic feel to the place. When it was all said and done I never thought about it again after lighting that first fire on a chilly fall evening.
Good luck and all the best-
Tom
http://countryplans.com/smf/index.php?topic=5327.20

ScottA · May 10, 2011, 12:43:39 PM

I ran mine straight up too. The single wall pipe is 14' long and I've not had any problems. Inside the house the pipe doesn't get cold enough to cause excess buildup, outside would be another matter. It also depends on how you use your stove. I like to make a hot fire when I first start the stove up to help keep the pipe clean. Using properly seasoned wood will help alot too. Most buildup issues are caused by using semi-wet wood IMO. If you're worried about it run double wall all the way to the stove but it will cost big bucks.

MushCreek · May 10, 2011, 03:48:51 PM

Slight thread re-direct: Will an outdoor run of pipe have more trouble with creosote build-up, due to the colder temperatures? My chimney (masonry, if I can swing it) will be pretty tall, going up past the ridge of a 2 story. And how do they sweep a tall chimney alongside a steep metal roof?

ScottA · May 10, 2011, 04:35:51 PM

A masonry chimeny shouldn't be a problem since the flue will heat up and stay hot for quiet a while due to the mass. To clean it someone has to climb up on the roof and push or pull a brush through the flue.

May 12, 2011, 12:42:09 AM

The tall single wall pipe can build up lots of creosote and the creosote will create an acid that wil eat the single wall pipe to paper thin in about 3 years - at least it does when burning Oak. I just replace it every so often. Double wall would be better stainless double wall better yet. I clean it aver couple of months in the winter.

AdironDoc · May 12, 2011, 12:15:24 PM

Neighbor says putting the stove in the corner, where the roofline is lowest is best but that the height of the flue above the roof still needs to be the height of the highest point of the house, like a chimney. That doesn't sound right or I'd end up with a short run inside, and a 16 foot length of stove pipe above the roofline. I'd need guy wires for that!

MountainDon · May 12, 2011, 12:25:03 PM

AdironDoc · May 12, 2011, 02:09:35 PM

Wow, Don. Thanks for the graphic. I think I'll just leave that stove in the center. With my roofline of 24' plus 2', I'd have at least 18ft of flue-pipe extending over the roof if put her in the corner. Now that would look odd if I could even get it not to fall. Plus, the creasote buildup from lower outdoor temps in the rise.

Doc