Fiber board or insulator brick?

[cecora]

I wonder could you use insulator brick in lieu of fiber board for the insulation between the concrete slab and the WFO floor ? If not wow ! That fiber board is pricey !!

[david s]

Yes, but insulating firebricks are even more expensive. I’ve got some free from old pottery kilns that have died and pulled them apart to use the bricks. The cheapest way apart from scoring free materials, is making your own vermicrete or perlcrete, but it has the problem of having to dry it out.