Insulation Efficiency Getting Started Discuss Insulation Efficiency in the Pizza Oven Design and Installation forums; Phil, 2" and hopefully you have some left over to make it 3" on top of the dome will DEFINETLY ...

[Dino_Pizza]

Phil,
2" and hopefully you have some left over to make it 3" on top of the dome will DEFINETLY be enough. You do not have to add vermiculite or vemiculite-concrete mix on top of that. I have this (mine is mostly 3"-4") with no other type of vermiculite on it. You can do the same and be fine.

Others have used the vermiculite-concrete below their oven floor, on top of the concrete base or inside the base and so they may have the stuff laying around and wanted to add more or just want to go the extra step of filling the void with vermiculite on top of everything. It will add some insulation value at relatively little cost, but I think with 2"-3" ceramic blanket, it will give you 95% of the heat retention you are looking for. -Dino

[dmun]

I thought that I read FB is now recomending Ceramic blanket only insulation. Has anyone else read this? If so, how much is required. The Ebook says 2 to 3 inches is enough

This is correct, and two inches would be enough for all practical purposes, but it doesn't come in a spherical shape, and it's hard to fit it to the dome without being lumpy. I think some builders aiming for the igloo finish have added vermiculite concrete just to get a smooth, uniform underlayment for the stucco.

[kebwi]

Excellent point dmun. Thank you (I'm weeks from that point, but stucco igloo is my intent, so I love the input).

[philiph4@ameritech.net]

Good point but in this case the vermiculite is not necesssary. Thick base coat for shape and and a final skin coat with stucco and I should be good.

Thanks,

Phil

[testadom]

OK, how important is the insulation, other than to make the oven more eficient? What was used before by the ancients. Can I just cover the dome with waterproof cement and go at it? Or will the heat crack it if it isn't insulated? How hot does the outside of the firebrick get if the inside is around 900 degrees?? My dome is about 4 1/2" thick.
I've just finished my dome and am about to start building the throat and chimney. I plan on curing the oven in about a week before covering it with either insulation or just cement. I want to cure it first so I can repair any cracks that might develop.
Any ideas or comments? They would be appreciated.

[jmhepworth]

Let me beat David. If you don't insulate, the oven won't work. You won't be able to get it hot enough because you will lose too much heat. And even if you could use enough wood to heat it up enough for pizza, it will be useless for anything else. Insulate, insulate, insulate.

Joe

[dmun]

Let me guess. There's no insulation under the floor either....

<beats head on desk>

Three years and more we've been doing this and still the message isn't getting out...

Insulate

Insulate

Insulate!!!!

[kebwi]

My guess would be that since the firebricks are basically heat sponges, then, if the inside is 900F and the oven has been heated up to full heat-storage capacity, the outside will also be 900F (the entire firebrick's mass is 900F evenly through) and both surfaces are evacuating heat in their respective directions with equal abandon. Hence ensue the problems associated with inadequate insulation.

I'm speculating, I don't really know, but it makes sense to me.

[testadom]

Actually, there is ceramic board under the floor. I guess I'll insulate the dome as I was planning to. It's getting towards winter here in the Northeast and I was hoping to get done a little quicker, trying to beat the cold. Any input as to using a WFO in winter around the Boston area. Any problems or procedures I should be aware of?

[ThisOldGarageNJ]

There have been many diff start up procedures for the cold... I start a little more slowly, Others jump right in with the fire from hell... My opinion is if your oven is properly cured you can probably start either way, I just prefer to heat up a little more slowly to avoid any thermal shock...
Mark