could I use these in place of the second floor slab?

[TylerDavis]

Ceramic Kiln Fire Brick K-23 IFB

K-23 straight IFBs (Insulating Fire Brick) 9"x4.5"x2.5"

I have heard a lot of people complain about insufficient insulation in the floor. I see these insulating firebricks for sale locally. Could I pour the normal 3" slab for the floor, then build the next layer out of these firebricks, before laying down the conducting firebricks for the oven? Skip the vermicrete / FB board and just use IFBs for that entire section?

Is this a good deal @ $2/piece?

[deejayoh]

Re: could I use these in place of the second floor slab?

you could use them, although I think you'd want to maybe lay them on edge. Check the ratings, I think IFB is less effective as an insulator than CF board, so you'll want more than 2.5".

$2 each is a good price for IFB, but how many of them does it take to make up the same area as a sheet of CF board? That's the price comparison I'd do. Check the prices of CF board at McGill's Warehouse.

[TylerDavis]

Re: could I use these in place of the second floor slab?

I looked up IFB properties and found thermal conductivity on the order of 0.3 W/mK. Forno Bravo board claims 0.13 W/mK. So yes IFB is slightly less but I think when you get below 1 W/mK it's a great insulator and you're splitting hairs to measure it out to two decimal points. Anyone have a # for 4:1 or 5:1 vermicrete?