Double dome with an air gap for a pizza oven?

[mark shinshu]

Hello,
Apologies in advance if this is a stupid question.

I'm interested in building a pizza oven, but would like it to be as small, light and movable as possible.

Has anyone tried making a double dome? i.e. an inside dome with a single opening at the front for air in/fuel in/smoke out, produce in/out. Then another larger dome above that, also with an opening at the front, and with a chimney at the top in the middle for the smoke to get out.

If it needs moving, the chimney, outer dome and inner dome can each be moved separately and single-handed.

There would be an air gap between inner and outer dome, with some smoke through it. It would be possible to add insulation blanket, or some mini walls between the domes, but since domes are self-supporting, there should be no need for anything structurally. Air is a pretty good insulator, so the insulation blanket may not improve insulation.

Where I live there can be a lot of rain and snow, and the top of a dome is susceptible to weather, so that is the best place to put the chimney.

I've been searching for other people who have tried this, but can't find any examples.

Is this a bad idea?

Mark

[david s]

While air is a pretty good insulator you really need a barrier to prevent heat travel by radiation and convection. What you have described is a squirrel tail oven, but they do have insulation between the inner and outer shells, just not where the flue travels over the dome. The tiled dome on this forum’’s title page is an example of one.

[mark shinshu]

Thanks David! I guess the insulation will reduce losses through radiation and convection. There should be less conduction with air though. Also, it's very easy to source air!

Is there any way of getting the incoming air to circulate between the domes before going into the fire?

That should reduce heat loss by convection since the heated air is going to end up in the fire.

[david s]

I don’t think you’d be gaining anything by doing that because cool incoming air on the outer surface of the inner dome would be cooling it. You’d be removing that stored heat only to be putting it back into the fire, nothing gained. Also air circulating in the space between the two domes would increase heat loss by convection.
Not saying your idea wouldn’t work, you’ll only find out by building it. Just remember that Italians are particularly ingenious (Ferrari, Lamborghini etc.) and have had a few thousand years on the design of these ovens, presumably with hundreds of variations. The hemisphere with a cross draft front flue has proved the test of time.