Deb Stephens wrote:I just had a thought. We dismantled an old glass kiln once and it had huge slabs of a material that was sort of like massive firebricks in it but they weren't the usual color. We figured they must have had some sort of insulative application. Could those be a mixture of clay with something fire-resistant and yet lightweight and insulative--like vermiculite or glass beads, etc.? Have you tried just googling firebrick images to see if you can find something similar?
Deb Stephens wrote:Those look like firebricks to me, but I'm certainly not an expert. The ones we have are yellowish-tan and have a groove on one side and a corresponding ridge on the other side so that they can be fitted together in the same way you would fit tongue and groove boards. Do yours have a ridge on the other side? Also, firebricks tend to be pretty heavy compared to regular clay bricks.
Daniel Ray wrote:6" is really shallow, what are your temperature lows? An insulation skirt around the footing will trap heat from the earth and prevent frost heave.
Abe Connally wrote:and here's from Ianto's book, Rocket Mass Heaters, page 23:
Abe Connally wrote:for the one below the feed tube, it will be 16 gauge metal, welded up to form a box. I may put a grill above it to prevent whole sticks from falling down in there.