web analytics
How big a vent for a 42" oven. - Forno Bravo Forum: The Wood-Fired Oven Community


1 of 3 < >

Forum Page Loading Response

Forum Members:

We have received feedback regarding recent issues with page loading response time. We believe the slow response issue stems from the analytics we added with the new Forum. We are in the process of reconfiguring those elements and, after an approximate 24-hour time period for the reconfiguration to run, we anticipate a return to normal page load times. Thank you for your patience!
2 of 3 < >


Hello, Forno Bravo Community Forum members.

As many may have noticed already, the Community Forum site was briefly down today. While working on scheduled routine maintenance, we encountered an error when trying to add a software update. As the site is now back up and running, some of you may notice that some recent data has been misplaced from November 10th up to today. We are currently working on resolving the issue. The forum has full operational capabilities and we encourage all forum members to continue actively posting in the threads.

We apologize for any inconvenience that this issue may have caused you. The Forno Bravo family values each and every member of our community. If you have any issues or concerns, please feel free to let us know on our issues thread here:


Thank you for understanding.
3 of 3 < >

Forno Bravo Forum Thread Message

Hello, Forno Bravo Community Forum Members!

The Forno Bravo team has heard the feedback in regards to the community forum. We wanted to take the time to re-enforce our commitment to a fully engaged Forum with professional moderation.

Our top priority as a company is to fix all forum errors and issues that you are experiencing. As we are swiftly working on these problems, we want to say that we highly value the Forum Bravo Community Forum and every single community forum member.

We have set up this thread so that every member can address any concerns, issues and questions about the forum. Please feel free to ask whatever you would like in regards to the forum; let us know what issues you are experiencing so we can work on resolving them as fast as possible. However, we stress that we would like constructive engagement, so please be specific about the issue you are experiencing.

Thank you for all of your patience and continued support.

Link to topic: http://www.fornobravo.com/community/...with-new-forum
See more
See less

How big a vent for a 42" oven.

  • Filter
  • Time
  • Show
Clear All
new posts

  • How big a vent for a 42" oven.

    Hello from Madison Wisconsin. My hopes for the Badgers football season are not very high so I've decided to focus on building an oven instead. I'm building a 42" Tuscan style dome oven (21" high), following the Forno Bravo plans (version 1.2) pretty close. The vermiculite insulating layer is poured and drying and now I need to lay out the oven, opening, etc. The insulating layer is 75 deep by 69 wide.

    For the opening I was planning on following the plans: so about 20" wide by 12" tall, square because we will make it from angle iron and brick of course.

    My question is about the vent size I should shoot for. I'm going to have a local shop fabricate a vent from SS and then use a commercial clay flue. The flue sizes are, according to my mason, 9 x 12, 12 x 12, 8 x 8. Those are OD measurements. I've got a call in to see about other sizes. Take away for the thickness of the clay and you have, I suppose a 7x10, 10x10, etc inside diameter for the flue.

    If the opening is 20", I imagine the vent will be about that wide, or 20".

    But what depth do I need to shoot for??? The pictures of steel vents in the plans are hard to follow, and I don't see any discussion of minimum sq inches of vent opening to get a good draw and keep the smoke from billowing out the opening arch. It seems logical that at some point it can get too big, but it also seems like more vent opening and a bigger flue size will lead to better draw and a better fire. My yard is sort of sheltered from the wind too, I might add.

    Anybody have an opinion, I'd love to hear it. I'm getting ready to outline the footprint so I need to set that vent depth pretty soon.

    P.S. Is it wise to "slope" the brick arch upward to the vent too??


  • #2
    Re: How big a vent for a 42&quot; oven.

    my understanding of vent design is basically the bigger the better, or the more volume at the start, the better, but I'm sure I'm oversimplifying. I my arch is 10-12"h x 18"w. My vent starts out just under 18 w. and tapers up to meet the 6"dia. anchor plate for my chimney over what amounts to about three courses of brick, or roughly 8". It draws beautifully with one 3' section of chimney.
    If your arch width is 20"id, then yea, I guess I'd spec that assuming it's going to have a flange to attach it to the brick. Based on my experience, I think whatever taper you put on it will be just fine, but I'm certain I read something here about vent volume vs. chimney diameter. If you can't find it, google might work.
    Last edited by splatgirl; 08-13-2009, 06:28 PM.


    • #3
      Re: How big a vent for a 42&quot; oven.

      There are rules about flue size in masonry fireplaces, where the flue area is a certain fraction of the fireplace opening. Since we have fairly small openings, we don't need huge flues. The 8 by 8 is what i used, and it draws like a champ, but my chimney is two stories tall which helps a lot. The rule of thumb about your transition is that the bottom should be twice the area of the top.
      My geodesic oven project: part 1, part 2


      • #4
        Re: How big a vent for a 42&quot; oven.

        For a 42 inch oven, I suggest about 60 to 80 square inches of vent funneling up to about 30 to 40 square inches of chimney.

        One other note. I see your dome is to be 42 inch. I suggest that the dome be elliptical in shape with a height about 85% to 90% of the radius which would be about 90% of 21 =18 3/4 inches in your case.

        Another dimension, and this one is critical to a well functioning dome oven, your door height should be 62% of your inside oven height. Or, in your case, 62% of 18 3/4 = 11 5/8 inches.
        Last edited by Neil2; 08-14-2009, 10:20 AM.


        • #5
          Re: How big a vent for a 42&quot; oven.

          I found this on an italian Oven building web site
          Diametro del forno diametro minimo canna fumaria in cm
          da 60 a 80 ----cm 20
          da 80 a 120--- cm 25
          da 120 cm in--- su 30