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  #11  
Old 09-23-2013, 04:58 PM
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Default Re: Insulation Thickness

The main difference, I imagine David S, is that a wood oven needs venting for cold air in and hot out. I guess the heat absorption of the walls is so important because it can quickly draw the heat out before it escapes out the chimney.

SO maybe it is important.
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  #12  
Old 09-23-2013, 08:02 PM
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Default Re: Insulation Thickness

Not only have I not seen an oven successfully built this way, I've seen one built this way that did not work.

A Few years ago a very respected member of another forum with multiple wood fired ovens and lots of wood fired oven knowledge had a small insulation only oven built to see how it would work. He had it built by a friend who had a business doing poured in place insulating chimneys using a very high quality insulating castable refractory. The refractory he used was a better insulator and stronger material then any other I have seen before or since. The resulting oven was beautifully built. It just didn't work. Problem being with no mass in the dome to store heat the floor quickly looses temperature and cannot regain it fast enough. That is why wood fired ovens have more mass in the doem then the floor. Heat rises, that heat is stored in the dome's mass. Heat also moves from hot to cold, so as the floor looses temperature the stored heat in the dome reheats it. The heat from the fire reheats the dome, because again, heat rises. With mass, insulation and fire you can keep this going perpetually. Without the mass it falls apart fast.

Don't reinvent the wheel. Build a low mass oven and insulate well. Instead of bricks halved making 4.5" of mass cut them in thirds for 3". For insulation most hardware stores now carry mineral wool batts with Roxul being the most common. It's cheap, efficient and able to handle the temperature. Use homebrew mortar to save more money. Insulate under the floor with perlite mixed with portland cement. I'd bet you can build the functional part of a 36" oven for about $250 this way, it will heat fast and work perfectly. Obviously the stand and finish will drive the cost up or way up depending on what you do, but you will need those with any oven.
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  #13  
Old 09-23-2013, 09:04 PM
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Default Re: Insulation Thickness

Great post shuboyje.

Not sure if I should just make a new thread, but on to another topic, alternate designs.

A barrel arch oven, because I like brick arches and domes sound a lot harder, with a trench in the middle, so you would put the food on some sort of slab over top of the trench, and the fire could be very easily tended and kept separate??

Not exactly sure what the difference is between dome and barrel, I am reading some things where people are listing all these difference that simply do not make any sense. I am thinking if you make them the same size, and mass that they should be identical except for shape.

Is this another stupid idea?
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  #14  
Old 09-23-2013, 09:45 PM
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Default Re: Insulation Thickness

Quote:
Originally Posted by wisnoskij View Post
The main difference, I imagine David S, is that a wood oven needs venting for cold air in and hot out. I guess the heat absorption of the walls is so important because it can quickly draw the heat out before it escapes out the chimney.

SO maybe it is important.
No difference really, I was thinking of LPG fired kilns using IFB's and they are the same, cold air in, hot out. The mass of the wares inside has the effect of storing thermal mass which you wouldn't have in an oven. I think Shuboyje has given you the definitive answer. It has been tried and doesn't work well. You would not be the first (me included) to think that you can improve on 2000 yrs of Roman ingenuity. Stick to the tried and proven that works.
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  #15  
Old 09-24-2013, 05:33 AM
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Join Date: Jun 2007
Location: South Carolina,USA
Posts: 1,910
Default Re: Insulation Thickness

Quote:
Originally Posted by wisnoskij View Post
Great post shuboyje.

Not sure if I should just make a new thread, but on to another topic, alternate designs.

A barrel arch oven, because I like brick arches and domes sound a lot harder, with a trench in the middle, so you would put the food on some sort of slab over top of the trench, and the fire could be very easily tended and kept separate??

Not exactly sure what the difference is between dome and barrel, I am reading some things where people are listing all these difference that simply do not make any sense. I am thinking if you make them the same size, and mass that they should be identical except for shape.

Is this another stupid idea?
A barrel vault is simpler to build than a dome, certain domes are easier to build than others. Like David said, you get the mass to temp and it doesn't matter much what shape you have.

What it comes down to is how you would like to use the oven. But for strictly pizza, low dome, thinner mass (2"-3") would be the most efficient. Insulation is a must for any oven that isn't used on a daily basis, which most home ovens are not.
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