Tell me that when you wrote "The Whitacre Greer firebricks have even lower conductivity" that you knew the difference was only 0.04 W/m-K.
In the past, whenever a material had more than one value for conductivity, I had always quoted the lowest. Prior to today, I had been using .625 as the value for W-G, but when you brought up the topic, I, in an effort to avoid contention, met you in the middle, so to speak, and went with the 'average' rather than .625. That was in error. .625 was the number I had in mind when I said "WG firebricks have even lower conductivity," and I should have stuck to my guns. Thank you for helping me find some backbone in this regard
Let the record show that when I said 'average,' I was erroneous. I consider, and have always considered W-G to have a conductivity of .625.
Regardless of whether or not W-G bricks are .625 or .657, lower, even fractionally lower, is significant. The only potential deck material with a lower conductivity than W-G and Fibrament is Biscotto, and Biscotto is neither logistically nor financially viable for domestic NY style pizzerias. The hair splitting that I'm doing here relates to awarding the crown to the viable material with the lowest conductivity. While it does lean a bit towards an ideal, there are real world ramifications. Most gas deck ovens are, as I said earlier, intrinsically imbalanced at higher temps. Neither W-G bricks OR fibrament resolves this imbalance. Your average deck oven owner can't purchase .6-.7ish decks and expect balanced bakes at higher temps. They are only a part of the potential solution. Because of this innate shortcoming at resolving balance issues, every fraction of a fraction of decreased conductivity matters.