design my chimney

[Timberjack]

I'm almost to the point of installing the wood stove.  Here's the info:  the stove drafts from the top and has a 6" flue.  I'm installing it in the corner of the room so my pipe clearance from the walls will be about 12-15".  I have a cathedral ceiling and it is about 20' from the top of the stove to the ceiling.  I'm building a nice floor pad and wall surround for the stove complete with concrete backer board and brick or tile. 

Questions:  I am considering using single wall pipe with pipe shield from stove top to just below ceiling where it ties into the chimney pipe but am wondering if I should just go ahead and use regular double wall pipe. 
Also, I notice where most codes require the top of the chimney to be at least 2' higher than any point on the roof within a horizontal distance of 10'.  I have no codes to satisfy and have a metal roof with 12/12 pitch.  This means that I will need about 12' feet of chimney pipe above the roof . Seems like overkill and a waste of money also.  How would you guys design this chimney setup?  Any and all comments or recommendations welcomed, thanks!     

[Redoverfarm]

Pros & Cons for using single wall pipe is that you will gain more heat in the room with the single wall.  But you need to allow sufficent clearance from anything that is combustionable.  There is some discusssion that there is more creasote buildup rather than double wall pipe which is insulated.

I would try to position the flue pipe where it exits the house (closer to the peak or ridge) to reduce the amount of pipe protruding above the roof.  There is a problem trying to anchor it.  Not to mention trying to clean the flue pipe.  

The 2' clearance is partly by code from combustion but more importantly the draft of the stove will be affected by not maintaining that protrusion above the highest portion of the roof.  Below that you could be prone to backdrafts and the stove not drawing properly and burning efficently. I had done a remodel on my house to incorporate a woodstove on a shed roof  (4/12) some 15' from my regular house roof (10/12).  Later I had to add an additional 7' in heigth to that flue just for that reason.

[Don_P]

The height requirement is for draft. alot depends on the prevailing... and occasional, wind. If the wind blows over the ridge it creates a roller just like the surf. when that roller gets to the chimney, if it is below the roller, the wind blows down the chimney causing a backdraft. Depending on the strength of the backdraft I've seen flames exit the stove's intakes, not to mention tons of smoke. The 2' above requirement is not always sufficient and is sometimes more than is functionally required. If the wind never comes from that direction you might get by with a shorter stack. In my case the "roof" above me is the mountain that rises about 400 more feet. Every few years we'll get a wind down the slope that requires opening the windows and doors to air it out. Haven't figuered out how to brace 402' of pipe yet  .

Check all clearances for the stove and pipe from combustables. I wouldn't crowd any of those dimensions.

[dug]

Technically you are not supposed to run more than 8 ft. of single wall pipe above the stove. You want to maintain a flue temperature of at least 300 degrees to avoid creosote buildup and with a long run of single wall pipe it is gong to be pretty cool near the top. Also a hotter flue will draft better.

I installed my stove before I knew better and have 16 ft. of single wall pipe going up to my cathedral ceiling. It drafts fine but we'll see how the creosote situation develops in due time. If I had it to do again I'd use double wall.

Like Redoverfarm suggested I would try to position the stove so the stack exits near the peak if possible.

[MountainDon]

have no codes to satisfy

The code you have to follow is whether or not the installation is safe and as trouble free as it can be. The funny thing is in most cases this will result in an installation that pretty much follows the "code". I believe this is one area where for certain there is good reason for whatever is written. Also read and follow what the manufacturer of the stove states about their product. What the clearances; they are minimums, a little more space never hurt anything.

Ditto what all the others said.

[Cowboy Billy]

I was going to put a wood stove in the corner of my pole barn. But my friend said that was a bad place to put it. He said I wanted to pipe to go through the roof as close to the ridge of the roof as possible. Because it put all the weight of the snow up the roof from the pipe against it. I haven't got the stove in yet but what he said makes sense to me.

Billy

[Squirl]

Great points made.  I dont' know if it was explicit, but I have seen a few on here change the location of the stove away from where the chimney exits with a 15-30 degree elbow.

[MountainDon]

Offsets should only be done with 15 or 30 degree elbows even though there are 45 degree elbows made. The 45's are not meant for wood stove chimneys. One other caveat is that there should be no more than 6 feet worth of straight pipe between the elbows, according to eveything I have read.

[Timberjack]

Thanks for the replys.  I did some measuring today and it looks like I need about 6' of chimney pipe above the roof to clear the ridge.  I think I can live with that.  I'm 'safety first' all the way but i also need to be practical and not go too far into debt just to be able to enjoy a wood fire.  At some point it becomes impractical and we will need to fall back on propane or electric.  I am leaning towards about 8' of single wall pipe then transitioning to double wall until we hit the class A chimney pipe.  Thanks for all the suggestions.   

[Shawn B]

I am leaning towards about 8' of single wall pipe then transitioning to double wall until we hit the class A chimney pipe.  Thanks for all the suggestions.   

I think you may have confused yourself on the flue pipe? Once you transition from single wall you must go to either Class A: Double Wall Insulated, Triple Wall Stainless or equiv. They make double wall insulted pipe in stainless and galvanized, so you can save money when running through a chase or attic. If you are referring to "regular" double wall pipe, non-insulated; that is Class B pipe, commonly called B-vent. It is for gas fired applications and should never be used on wood burning fireplaces. The inner liner is only aluminum and will not hold up to the high heat of wood. Maybe I did not understand your above statement? Again once you transition from single wall pipe stick with Class A all the way up through the roof. It's your choice of either insulated pipe or triple wall stainless, both work fine.

[Timberjack]

Thanks Shawn, I should have been more clear, I was referring to class A double wall insulated pipe.

[Sassy]

Offsets should only be done with 15 or 30 degree elbows even though there are 45 degree elbows made. The 45's are not meant for wood stove chimneys. One other caveat is that there should be no more than 6 feet worth of straight pipe between the elbows, according to eveything I have read. 

Don, you don't want to know what we've done     with an underground house you gotta have the offsets or you might have mud dripping on your head 

[MountainDon]

The underground complex is special in many ways. And, well, complex.