Chimney install questions

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b33p3r

Feeling the Heat
Jan 29, 2008
286
NE Pa
Checked out chimney pipe when a friend suggested I build a more permanent chimney with chimney block and flue liner. Looks like self build will be 1/3 the price. Any pros or cons anyone can think of. Also I'm building in a shed with a 6/12 roof. The chimney would be 1 ft inside the wall on the low side of the roof. I figure I'm looking at 13' of chimney from the floor. The stove pipe exits the econoburn at about 4 ft. 13'-4' would be 9' of vertical flue to pull a draft. Would that be enough? I will be installing a barometric damper. Flue is 8".
No, econoburn doesn't call out a minimum heigth. They just say "enough" to get the proper draft.
Thanks in advance.
 
Anybody? My big concern is whether 9' vertical 8" flue would supply enough draft?
 
b33p3r said:
Checked out chimney pipe when a friend suggested I build a more permanent chimney with chimney block and flue liner. Looks like self build will be 1/3 the price. Any pros or cons anyone can think of. Also I'm building in a shed with a 6/12 roof. The chimney would be 1 ft inside the wall on the low side of the roof. I figure I'm looking at 13' of chimney from the floor. The stove pipe exits the econoburn at about 4 ft. 13'-4' would be 9' of vertical flue to pull a draft. Would that be enough? I will be installing a barometric damper. Flue is 8".
No, econoburn doesn't call out a minimum heigth. They just say "enough" to get the proper draft.
Thanks in advance.

Selkirk has kindly provided the straight dope on this topic. Go to

http://www.selkirkcorp.com/Metalbest/Product.aspx?id=210

and pull up the “Chimney & Venting Sizing Handbook” from the Resources ‘View Documents’ javascript menu.

Go to Section 11 and set up a spreadsheet to work with the ‘The Chimney Design Equation’. They have a cascading chart set up for doing the same thing, but I’d say a spreadsheet is a lot nicer for adjusting the individual factors to see what effect they have and to see how much trouble you might be in if you’ve estimated a factor incorrectly.

The critical factors are having a good ‘k’ or flow resistance estimate according to the tee, elbows, and piping length involved; and knowing what what the manufacturer specifies as the amount of draft the appliance should see at its outlet, which can vary a lot.

Short answer, I'm going with 6 inch flue, 8 ft insulated on top of 2.5 ft near-boiler stove pipe, with one elbow to go from boiler output horizontal to flue vertical. According to the Selkirk formulas this should be plenty for 120000 btu / hour gross given the draft specification for my boiler.

Cheers —ewd
 
Long list of variables, Beeper. Chimney draft is a vague science.

Shed roofs (or any roof for that matter) have strange aerodynamics at certain wind directions. I'd recommend a good cap on top based on some frustrating experiences I've had. In my case it was a Metalbestos cap and the back-blow problems went away. But then, the very expensive thing was given to me.

I can tell you that a masonry chimney will draw better after it gets warmed up. If you put in an ash clean-out door at the bottom you can get the draft running with some newspaper and splints before you kindle the Econoburn if it gives you trouble starting in the worst conditions. Then you can add on to the height when the weather allows.
 
if you are build a fire place use chimney block/brick , if you are putting in a wood burning stove/boiler use a factory made chimney, 30 bucks a ft ,don't think you can do block/brick any cheaper then that. The all fuel metal chimneys last forever, better draft, easier to clean and because they work so much better cleaning is seldom required.
 
Nobody who has ever carried a concrete chimney block up a ladder and tried to carefully set it down on a ribbon of fresh mortar will argue that Selkirk/Metalbestos type (class A?) chimney isn't a whole lot easier.

And I'm sure it will almost always work much more efficiently for a given height. But the stuff is running about $40/ft. around here. And the brackets and flashing and etc. are murder on the wallet,too.

For the guy trying to save money, block-and-tile can work well. I think, though, that it's harder to design for adequate draft with that larger mass and lower insulation value. And once it is outdoors and exposed to the cold adding on more height is less effective.

My chimney is 32ft. tall up the middle of the house. Block/tile then transitioning to Melalbestos in the cold attic and out the top to the cap. Back when I built it the price difference overwhelmed my budget. If I were doing it now, I would go Selkirk all the way.
 
Lots of great responses. Everyone of them. I was looking at the selkirk ($1200.00 approx.) then pieced together a dura techsystem ($700.00 +). So I was kinda leaning towards the less expensive but even then I was going with the more expensive SS Pipe. Some of the pieces these packages include I don't need since insulation in attic and such won't be an issue for my shed.
I really don't feel like lifting heavy blocks but I figured I'd throw it out there. I got prices on Chimney block , flue liner, clean out door and thimble, < $300. It would also set me back a week or two while I build it as opposed to snapping together a pipe system. My friend just thought it would be a more permanent and cheaper install as opposed to replacing rotted pipes now and again. But from what you guys are telling me, the pricier SS insulated pipes are holding up real good.
E.W. Thanks for the spreadsheet info. I'll run the numbers.
Thanks to all
 
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