Chimney length and curve

[mrotter]

I plan to build pizza oven using FB great DIY PDF plan/tutorial. I have one little thing to solve beforehand.

The place the oven will sit in is now under construction - I am building "pergola"-like structure with transparent roof (glass or polycarbonate) so now I am before some decisions:

1. Oven chimney cannot go through glass/polycarbonate roof, or atleast I did find any solution...
2. As the oven will be placed near the edge of the roof the chimney will need to have 45-60 degree curve/bend on its track, will this damage the overall oven performance?
3. If 2 is doable will longer/higher chimney subsequently help to improve baking performance?

[SableSprings]

Welcome to the forum family! Many ovens here have been built with an angled chimney. Putting such an angle on your flue will not reduce oven performance. It is important to plan the correct size of your chimney system.For ovens at 36" internal diameter or less, a six inch (id) flue works very well. If you go for a larger oven, then an 8 inch id chimney/flue is recommended. The main purpose of the chimney is to simply keep the smoke out of your eyes during initial firing. There is a commonly used design that has the chimney angled back over the dome so it appears to exit at the top of the dome...it's called a squirrel tail chimney.

My wife did not want me to use any sort of transparent roof material because "stuff" builds up on it constantly & it loses it's charm pretty quickly when a flock of starlings "passes". If you do opt for clear roofing, do be aware that you want the roof to drain away from the oven & have enough overhang so you don't create a drip line across the dome.

Hope that answers your first questions...we're here to help, so spend some serious time looking at builds here so you have a solid idea of what's going to work best for you.

[mrotter]

Yes, your reply makes things much clearer for me as I would much rather incorporate some curves into the chimney than making holes into glass/polycarbonate roof, not only it is much more work but it is also more expensive.

[MarkJerling]

My oven's chimney curves up over the dome. It works well. If you can make the height work, then a 45 degree slope would be the lowest you should try to go.

[JRPizza]

If you are using an off the shelf type of chimney pipe the manufacturer usually has published specifications on how to make an angled or horizontal run of pipe. Their recommendations are a good starting point. Where I live the building codes are usually copies of what the manufacturer recommends.

[UtahBeehiver]

If you look at the latest post by Mullster you can see his oven vent going through polycarb or something similar.

[david s]

I've built a few ovens which penetrated the roof. Apart from having to use a double flue to overcome heat issues from the pipe, it introduces sealing issues and corrosive soot dropping from the flue cap onto the roof surrounding the seal. I prefer to track the flue up and beside the gutter so it's at least 50 mm away from the gutter and 600mm above it. Some folk don't like the look of all that flue, it doesn't bother me and I prefer function above appearance. This method allows the oven to be tucked under the eaves, giving it pretty good weather protection, utilising a single walled flue pipe, keeping the operator out of the rain, whilst not penetrating the roof.

The flue pipe should never be horizontal (although I've seen quite a few that are). No flatter than 45 degrees will not disturb good draw.

[JRPizza]

I put my chimney up through my roof but did consider doing an offset pipe like david s shows above. We get considerable rain in the winter, accompanied by wind, which seems to come in at a 45 degree angle most of the time. We needed a back wall to block the wind and keep from soaking the rear of the dome and wetting the hearth slab, so were going to have to have a penetration in one direction or the other. If you leave the rear open you will probably want to so some moisture preventative measures like weep holes, raised insulation, and water resistant coatings.
We were considering a transparent(ish) roof like you but switched to metal because of the penetration. Just could not figure out how to make it work without having to do something local around the pipe that we thought would not be visibly appealing.

[mrotter]

I've built a few ovens which penetrated the roof. Apart from having to use a double flue to overcome heat issues from the pipe, it introduces sealing issues and corrosive soot dropping from the flue cap onto the roof surrounding the seal. I prefer to track the flue up and beside the gutter so it's at least 50 mm away from the gutter and 600mm above it. Some folk don't like the look of all that flue, it doesn't bother me and I prefer function above appearance. This method allows the oven to be tucked under the eaves, giving it pretty good weather protection, utilising a single walled flue pipe, keeping the operator out of the rain, whilst not penetrating the roof.

The flue pipe should never be horizontal (although I've seen quite a few that are). No flatter than 45 degrees will not disturb good draw.

Thank you very much. Your photos along with 45 deg. angles are exactly the inspiration I was looking for. I do not plan to have any horizontal parts in chimney, two 45 angles will probably work just nice.

[mrotter]

I put my chimney up through my roof but did consider doing an offset pipe like david s shows above. We get considerable rain in the winter, accompanied by wind, which seems to come in at a 45 degree angle most of the time. We needed a back wall to block the wind and keep from soaking the rear of the dome and wetting the hearth slab, so were going to have to have a penetration in one direction or the other. If you leave the rear open you will probably want to so some moisture preventative measures like weep holes, raised insulation, and water resistant coatings.
We were considering a transparent(ish) roof like you but switched to metal because of the penetration. Just could not figure out how to make it work without having to do something local around the pipe that we thought would not be visibly appealing.

Yes. I plan to make wooden wall (in proper distance) behind my oven, for the exact purpose - keep windy rain from the oven, although the roof itself will overextend over the surface by quite a distance.