Hearth design question for future WFO build

[sydney home cook]

Hi everyone, i am in the process of doing my research for a future build of a brick Pompeii style WFO.

my goal is to have extra cooking time for slow cooking roasts and breads well after a pizza fire up. exeeding retained heat past 72 hrs if possible.

Has anyone insulated their oven floor in the following way mentioned below?

On top of the structural concrete slab which will set on concrete besser blocks, using the white insulating firebricks, then on top of that using a 50mm calim silicate board then on top of that placing a full size oven brick in herringbone format (75mm thick brick).

Oven kit i am looking at is the 1200 POMPEII.

Would be appreciated if you can provide some feedback on this,

Cheers,

[Sixto]

Hi Sydney, I did something similar to what you mention, except I omitted the calcium silicate board, and placed my hearth bricks above 2 layers (4.25") of insulating firebrick. Also my hearth brick were placed on edge, so there is 4.5" of heat storage directly under the fire. (wanted to store heat evenly all around) The oven works well and retains plenty of heat for lower temp cooking the second and third day, but takes longer to get up to pizza temps. Heat rises, so you will get more bang for the buck for every inch of insulation above the floor, around the outside of the dome. (I find 4" is the point of diminishing returns) I separated my floor bricks from the dome by inserting a 1/8" thick corrugated cardboard spacer between them, and created a thermal break between the dome and the arch/flue using a rope gasket. Also having a well-insulated door is critical so you can reduce heat loss through the arch (that's where I notice the majority of the heat goes out of the dome). The hottest my dome surface gets is about 10f above ambient temp, and I have about 4" of blanket insulation, 2" of perlcrete, and 1" of stucco on top of my firebrick dome.

Enjoy the journey! - Six.

[sydney home cook]

Appreciate the update. Will keep on doing my research and learning things till the time comes to start the project. Cheers