Minor question about insulation

[kebwi]

I have three inches of insulating board...so the bottom face of my floor and of the surrounding base wall of the dome start three inches from the hearth. When I wrap the dome in a few inches of InsWool do I need to insulate below the three inch mark, which is an area that will have no direct exposure to the firebricks...or can I fill that area with, say, gravel, so as to save the InsWool for other parts of the construction?

[Fairview WFO]

Re: Minor question about insulation

Your walls and floor all store heat and will loose heat on the backside. So you want to insulate all around, even if its not directly across from exposure to fire on the inside, its still part of the thermal mass and heat storage. Kinda like hanging your trap door open on your thermals if you know what I mean?

[kebwi]

Re: Minor question about insulation

Yeah, I'm leaning toward filling that bottom three inches with loose (packed) vermiculite. I don't really want to pack the InsWool right down to the hearth. It seems wasteful, and furthermore, I'm not sure I should have fluffy stuff at the hearth, which it might get wet from seeping water. Vermiculate, then fluff from there on up is what I'm thinking.

BTW, gorgeous oven.