Rockwool for hearth insulation

[gorazdr]

Hello,

I am new to this forum and starting my WFO build.

I would like to know if this can be used for hearth insulation http://www.knaufinsulation-process-s...eb-1213-UK.pdf

it is rated up to 700 C / 1300 F

Thanks, Gorazd

[david s]

Re: Rockwool for hearth insulation

Rock wool is not quite as good an insulator as calcium silicate board, but it's cheaper.i've used rock wool blanket but it has the reputation of being extremely water absorbent, although I notice your product claims to be water resistant, they probably have treated it with something. The main thing I'd be concerned about is its strength. Will it be strong enough to withstand the weight of an oven built on top of it without compressing?
Most builders go for calcium silicate board under the floor or if you want a cheaper way of doing it cast your own vermicrete slab using a 5:1 ratio.vermiculite, cement.

[v12spirit]

Re: Rockwool for hearth insulation

I haven't seen rock wool insulation that comes in boards. I could only find rock wool blankets. Good for you to find one. I agree with david s. I think that Vermiculite or Perlite in the ratio 5:1 with cement would be cheaper and better than the rock wool board. I even had several weeks delay in my build looking for hearth insulation. If I find one I'll be done in a week or two.

[gorazdr]

Re: Rockwool for hearth insulation

Thanks for your inputs. I finaly found some specs about load bearing properties and it is not going to work. High temp board has compression strength of only 250Pa, normal rockwool board is 2MPa.

Gorazd