I personally don't understand the insulation on the bottom of a firebox. Heat rises and therefore if you want to retain it you would insulate the top if nothing else. The advantage has got to minimal at best and snake oil at its worst.sandro wrote:Some pit builders insulate the bottom of the firebox to retain heat from the coal bed (ie: Fat Stack); however I don't think it's that much of a game changer beyond the first couple of hours of cook—it won't be long until you'll have a good thick layer of ashes between the live coals and the metal. That said, firebricks are so cheap I wouldn't even bother discussing it, get some and try. RaleighSmoke had good results on his Brazos! https://www.youtube.com/watch?v=e6HI-EhQVME
Maybe a bit, hard to tell. I've never paid that much attention and they're all pretty efficient in that a pretty small fire in there to keep them running at temp (which is definitely easier to maintain) Certainly more problematic trying to keep a coal bed without the bricks.