Is a chimney required?

[ned]

Or is it's function simply to reduce the hot air and smoke from exiting the oven door (and therefore make the oven door less smoke stained and human friendly)? This is assuming we are talking about an outdoor oven - of course.

I have seen pictures of ovens built w/out chimneys, but I have been unable to find out any specific details about design/function issues in that context.

A related question has to do with the 60% height ratio (top of oven door to oven peak) - how does the elevation of the chimney intake relate to the top of the inside of the oven? Is it the same as the oven door, or does it matter?

Thanks

[Nic The Landscaper]

Re: Is a chimney required?

Chimneys serve 3 purposes.

The first, and most obvious is to make the wood fired oven a more people friendly experience. There is nothing worse than a face full of smoke while trying to work the oven.

Second, the drawing action of a chimney will improve the convection current inside the oven, which will make your fuel burn more efficiently (hotter with less smoke.)

The final reason for a chimney is safety, and this will be dictated by your local fire codes (which from what it looks like your in sw Washington so codes are about the same as here.) Around here any wood burning appliance within 10 feet of any structure must have a chimney that terminates at least 2 feet above the structure.

There are formulas for calculating the draw efficiency of a chimney, but for the purposes of a wood fired oven anything less that 3 feet, really is not adding much of a draw, but it still will serve well to direct most of the exhaust gases away from people. The more important correlation to consider is pipe diameter, and to get to the point, an 8 inch diameter, round or square flue liner is ideal for all wood ovens.

[nissanneill]

Re: Is a chimney required?

Ned,
don't even think of building an oven without an efficient chimney!
Apart from the benefits that Nic mentioned, personal safety is even more important.
As an example, say you get your oven to 500˚C as I do and you put your fire to one side, and reach closer to sweep the hearth in readiness for your pizzas, you put your face a little too close and scorch your face, blistering it severely. Goodbye pizza fest and hello hospital and weeks/months of recovery.
Just not worth the trouble.

Neill