Chimney and cupola

[dsimonl]

I am planning a woodstove installation in our barn. The duravent chimney will have a straight run through the second floor loft and out the roof. The barn has a 4x4 cupula on the barn roof ridge. Do the 2/3/10 rules apply to the cupula? In other words, do I need to be 2 feet above the cupola roof within 10ft?

Thanks.

 

[oconnor]

I would have to say yes - the issue is wind interference, and likely a measure of fire safety in a chimney fire too, so I'd suggest the rule applies to any roof surface. Not sure of the specifics of the code, but that would be my logical approach.

Edit - Probably already in your plans but, I might also add that you consider a chase around the chimney in the loft to keep items from hitting it and keep them outside the 2" airspace needed - would hate to see it damaged or cause a fire.

 

[dsimonl]

Thanks. That's what I guessed....just wanted to confirm. I have plenty of space to offset the penetration so it is >10' from the cupula. Would it be best to do the offset in the heated area with single wall, or use the chimney pipe in the loft? Total single wall length w/offset would be ~12'.

Edit:

Excellent idea re: chase in loft. It is now in the plan!

 

[begreen]

A long length of single-wall is going to cool down the flue gases significantly. How tall will the flue be? How much in the interior of the barn? If the pipe is going to be penetrating a floor, like the loft, it should transition to class A at that point. I'd also put it in a safe chase to protect against anything getting too close to it, especially if hay is stored in the loft.

 

[dsimonl]

The original plan was: 6' of straight single wall flue to the class A chimney transition. The chimney will consist of: 8' through the loft, 2.5' through the attic, and 4.5' above the roof.

NOW, based on the cupula, I will need to be 8' above the roof. Yuk! Thus the query about an offset.

 

[begreen]

OK, that's not too bad for the vertical, but 12' horizontally is not good. Ideally you don't want the horiz run to be more than a few feet. You could do the offset diagonally to maintain good draft, but it doesn't sound like you have the height under the loft to achieve this. Also, single wall needs to be kept at least 18" from combustibles.

Are there other options? Could the stove be placed on the opposite end of the barn and cupola?

 

[dsimonl]

Placing the stove on the opposite end IS an option, but not ideal. Right now it is fairly centered in the space. The horizontal run would be 4-6'....the TOTAL single wall (horizontal and vertical) would be 12'.

Another option is placing the stove along an outside wall. But then >50% of the chimney would be outside the building....also not ideal.

 

[begreen]

How about putting the stove centered and running the stack up through the cupola roof?

 

[dsimonl]

I love the way you think!! I'll have to check the construction and see if that will require an additional firestop, and whether there is enough roofing for the flashing.

Thanks!

 

[fossil]

If you do that...through the cupola...keep in mind that the chimney then must rise another 3' above the cupola roof. Rick

 

[dsimonl]

Yeah, I was looking at that. I think my best bet at this point is placing the stove against an outside wall. The single wall flue will go straight up 6' into the class A transition. Then the chimney will go 4' through the loft and up an additonal 8' after the roof penetration. I am considering triple wall chimney for better draft since so much of it is outside the building.

 

[fossil]

If you need to go 8' above the roof penetration, you'll need to brace it. I'd think that Class A chimney would be fine (double-wall insulated). Is the 8' driven by the roof pitch, and getting 2' above anything within 10' horizontally? Sounds like a steep roof. Any pics of the building (inside & out) that you could post? Rick

 

[dsimonl]

You are correct, it is steep. The roof is a gambrel. The penetration point at the outside wall has a 19.33/12 slope!

I'm planning on 1 support.

 

[fossil]

I know gambrels. Sounds like a real pretty barn. Rick