Foam Glass Question

[CoastalPizza]

...service temp dropped to mid 700 F when loaded. This could be a concern since these ovens are so heavy. You would certainly not want the FoamGlas to fail and the oven shift. As David suggest, a small layer of Vcrete would take care of this and act as a temperature buffer.

That is what I did - I added a 2" layer of perlcrete (5:1) over the Foamglas. Since I planned for this, the height of the oven floor bricks was just as I planned. The perlcrete over the Foamglas gives me a bit more thermal mass in the floor (since 5:1 perlcrete isn't the world's best insulator) and ensures that the Foamglas doesn't get too hot and start flowing.

[Michael Harrington]

I talked to corning and they said compressive strength 90lb /in but is reduced with heat plus what Russel and dave said about weight so what wood be best insulation as far as water resistant should Iuse.I have 12 sheets of 18x24 foam glass enough I think for 4.5 in under floor .What wood be best way to use all of it is 4.5 +2in of other insulation to much.Thank everyone for all your advice.

[UtahBeehiver]

So why are you wanting use wood and where in the layers are you thinking you need to place? Again, why are you not just putting a CaSi layer under the bricks or if that is out of budget, put a vcrete layer in. I am not sure why you feel you need to install all the FoamGlas. You got it for such a cheap price anyway.

[CoastalPizza]

See post #9 in the link below for how to cover the FoamGlas with perlcrete.

[Michael Harrington]

I am sorry what I meant was what insulation would be better as far as being water resistant the CaSi or vcrete . The other question is with 1 inch of other insulation should i still use all foamglas it would make it 5.5 inch under floor is that to much .If not what else am i going to use it for. Thanks

[Michael Harrington]

I hate to ask again but can anyone answer my question about best insulation that is the most waterproof and is 4.5 foamglas plus 1" casi or vcrete to much see above post. Thank YOU

[Michael Harrington]

Ok I will put it another way I have enough foamglas to have 4.5 " for under the floor going to add 1'' of either casi or vcerte on top of that so what I want to know which insulation is better as far as being more waterproof and is 4.5'' of foamglas plus 1 '' casi or vcrerte too much. Thank you please help.

[CoastalPizza]

Once cured, the v-crete will be more water resistant than the calsil.

[Michael Harrington]

Thank you CoastalPizza so v-crete is what I will use. The other part of the of question I have enough foamglas for 4.5 inches with the v-crete one or two inches don't know how much to use of the v-crete should I use all of foamglas or just 3'' and the v-crete .I would not have no other use for the glass but if it would be too much I will not use all 4.5''. They say you cannot have too much insulation but too much maybe too much?

[SableSprings]

In answering how much base insulation to use, the question that needs to be asked is "Will that total of 5.5" underneath your cooking floor make your oven too high to work?" The 3" of Foamglas + 1" of v-crete is really plenty insulation for normal, extended cooking/heat retention.

Definitely having the inch of v-crete on top of the Foamglas to "buffer" the heat is important, but using all 4.5" of the Foamglas plus and inch of v-crete is totally overkill in terms of the advantage (IMHO). Since you have the product on hand, it certainly wouldn't hurt to use it...however, I'd probably save "a layer" for building/insulating a fire door. Hope that helps in your decision.

[Michael Harrington]

I found firebrick on craiglist it has FNS 30 42 stamped on it does anyone know what kind of bricks they are. Someone online said they are made by premier refractories. Thank you