Chimney Placement - Front or Middle?

[wthwaites]

Hi all,

I've been reading threads but can't seem to find an answer so I hope I will have some luck with asking myself...
Is there any difference between installing the chimney directly over the vent opening at the front of the oven vs channeling to the top/middle of the dome area from the front? I'm looking for the better of the two. Or is placement purely aesthetic?
I'm currently building a 42" oven and approaching the step for installing the chimney. I iprobably do more baking and roasts in comparison to cooking pizzas (but that may change? you never know!).

[mongota]

If you're talking about the vent opening itself being over the landing and the only difference being the chimney extending vertically up over the landing versus the chimney 'squirrel tailing' back over the exterior of the dome so the chimney extends up vertically above the dome itself, it's a bit of a draft thing and a construction thing regarding transmitting loads. You'll get a slightly better draft and an easier build with the vertical versus the squirrel tail. But the difference should not be enough to deter you from pursuing a squirrel tail chimney if that's what you desire.

My opinion.

[wthwaites]

Yes, a "squirrel tail" is what I'm referring to vs vertically straight above the landing.

Thanks for the feedback!

[fhausback]

Everything I've read says the squirrel tail performs just as well as the straight flue, but construction is much more complex. I'm going squirrel tail because it will give my chimney some clearance off a future patio roof, while keeping the oven opening out of the rain (if there is no wind).

[MarkJerling]

Hi all,

I've been reading threads but can't seem to find an answer so I hope I will have some luck with asking myself...
Is there any difference between installing the chimney directly over the vent opening at the front of the oven vs channeling to the top/middle of the dome area from the front? I'm looking for the better of the two. Or is placement purely aesthetic?
I'm currently building a 42" oven and approaching the step for installing the chimney. I iprobably do more baking and roasts in comparison to cooking pizzas (but that may change? you never know!).

I curved my chimney back over the dome. Some say that it helps to heat the dome as the "lost" chimney heat helps to heat the dome. If you'd like to see how I did it, check out my build photos and my oven drawings: My oven drawings - Forno Bravo Forum: The Wood-Fired Oven Community

I did not find it particularly difficult to do and, in my case, I did not want the flue directly above the vent as that would have placed the flue in line with a window.

The only disadvantage I can see, of doing it the way I did, is that the part of the chimney curving up over the dome would be very difficult to sweep. But, at the same time, the top of the dome gets so hot that soot should burn off in there, so maybe it's not a problem. I need to stick a camera in there to check!

[wthwaites]

With the squirrel tail design, wouldn't it be a better idea to construct the chimney channel after you have insulated the dome with Fire blankets and rendered the exterior wall? That way you would eliminate the issue of heat loss, right?

[MarkJerling]

With the squirrel tail design, wouldn't it be a better idea to construct the chimney channel after you have insulated the dome with Fire blankets and rendered the exterior wall? That way you would eliminate the issue of heat loss, right?

Heat loss is not a problem with the "squirrel tail" design. Heat going up the chimney helps to heat the dome, so there's no need for insulation between the dome and the chimney. A large part of the chimney construction becomes part of the thermal mass of the oven dome and insulation over the whole prevents heat loss. I would not want to place the chimney structure on top of insulation blanket as I do not think it would be a structurally sound construction.

[wthwaites]

Heat loss is not a problem with the "squirrel tail" design. Heat going up the chimney helps to heat the dome, so there's no need for insulation between the dome and the chimney. A large part of the chimney construction becomes part of the thermal mass of the oven dome and insulation over the whole prevents heat loss. I would not want to place the chimney structure on top of insulation blanket as I do not think it would be a structurally sound construction.

I remember seeing in a couple threads that heat loss is an issue with this design specifically with baking breads and doing slow roasts as the oven cools down after firing. Perhaps I read wrong...
Installing on top of the exterior wall after insulation and then adding additional perlite/concrete render would stil be considered structurally unsound??? Wow.

[MarkJerling]

I remember seeing in a couple threads that heat loss is an issue with this design specifically with baking breads and doing slow roasts as the oven cools down after firing. Perhaps I read wrong...
Installing on top of the exterior wall after insulation and then adding additional perlite/concrete render would stil be considered structurally unsound??? Wow.

My concern is with placing the (heavy) chimney structure on top of blanket. If I have misunderstood your post, then please accept my apologies.

With door fitted, I find that my oven is at 260degC/500F after 12 hours, 350F after 24 hours, 250F after 36 hours and 200F after 48 hours, this being time after finishing making pizzas and fitting the door. With that sort of heat retention I don't see a benefit in separating the chimney structure, thermally, from the top of the dome.

[wthwaites]

Thanks for the advice Mark! No apologies needed.

[MarkJerling]

Thanks for the advice Mark! No apologies needed.

No worries. Here's a a photo looking up the chimney as it curves up to the top of the dome. I'm surprised how little soot there is in there. I suspect that the heat of the dome simply burns the soot off.

[wthwaites]

This is good to know. I assumed so as well!
How long have you had your oven for?

[MarkJerling]

This is good to know. I assumed so as well!
How long have you had your oven for?

We started building in March, then Covid so could not get materials until end of May, so mainly from May to end of September So, have been using it now since early October. Not that long, but we're really enjoying it.