alternative cheap insulation?

[SCChris]

John, I went to Pacific Insulation in San Pedro or there abouts.

Under the oven I went with 2" rigid SiCal.
Around the oven I went with stonewool in direct contact with the dome and tucked into what gaps there were.
In the corners of the structure I went with 8" non-faced fiberglass insulation it was quickly available and since it wasn't going to have high heat, binders burning weren't and won't be an issue- Lowes
Once I had tucked and stuffed these I poured vermiculite into structure to fill the little gaps.

Chris

PS. I thought I’d also pass along that high density Stonewool board is used as a base for stucco, so stability souldn't be an issue. I haven’t seen it but given the density, it seems to me that it could work under the oven floor. I’d start with the manufacture and verify stability and lack of toxicity of binders at something over 900F, if they are present. I’d want to bring the whole oven to high heat for several hours to verify that anything that might need cooking out does. The last thing anyone needs is an oven that isn't usable because of outgassing of sub-floor insulation. Again, I’d start with the manufacture.

[Giulio]

Originally Posted by chidding

Why not opt for a cheaper brick? This is how I saved alot in my project..
Sure i may not be using firebricks, but I'm sure with solid clay bricks im going to get pretty damn close.

No matter what you do.. dont skimp on insulation.. its the single most important aspect.

couldnt agree more
used solid reds for floor and dome,goes like a bomb!
insulation is crucial!
an Italian freind has had an oven made of red brick for 17 yrs that is 2 meters wide and used 3 times a week for semi-commercial bread making.It was recently rebuilt with same bricks as the base was rusting!
Mortar used was clay slurry from back yard
any oven you can afford and have immediatly is better than one you cant afford

[SCChris]

These folks might have access to chipped and otherwise, in their opinion, inferior firebrick. I also remember some in the UK using "Heater Brick" as a cheaper alternative, although I don't find the thread right now.


Firebacks, Fire Bricks, Flues, Pots, Grates, Tiles And Refractory Products Dineen Sales Ireland

Chris

[sonomacast]

Why not use normal bricks for the dome, i did and had no problems (get russel jeavons book) also you could use (kingspan Insulation) that is made in Dublin and there is allways loads left after a job which gets skipped, I used it on my first oven and it worked a treat. I would use firebrick on the slab though. But possibly engineering brick would work in thoery as it is fired to such a high temperature in its manufacture, good luck with everything

[wotavidone]

Whilst lying abed wishing my various illnesses would go away and bother some other poor bugger, I've drawn out my oven to scale, and made some decisions about materials.
I've also done quite a bit of web surfing, and came across a small tidbit of information. Scoria makes a good fire proof insulator apparently. This was on a site discussing insulating forges and kilns.
By scoria, I mean that very porous rock formed when dissolved gasses are ejected as lava solidifies. See wikipedia.
Not pumice, which is so light it floats, but still very much full of air holes.
Over here in OZ we get scoria rock, which I guess must be the same thing, by the trailer load to use as a landscaping groundcover. It can also be bought in bags for use in BBQ grills between the burner and the grill.
If you have the same sort of thing in the Emerald Isles, maybe you can try a sort of scoriacrete instead of vermicrete, if its cheaper.
As Billy Connolly, my very favourite comedian, once said while discussing Tarantulas and their wiley ways, "I've not tried it myself".
Regards,
Mick

[asudavew]

I looked into using lava rock.... it's cheaper. And I'm not so sure it wouldn't work well.

[wotavidone]

Catacomb, Scoria has real possibilities as a cheap insulator.
http://www.fornobravo.com/forum/f8/lava-2487.html (Lava?) (Lava?)
Thanks to dave for this

[wotavidone]

this is an excellent article.
http://www.academicjournals.org/IJPS...ep/Hossain.pdf
dave's work again

[david s]

Great find, interesting reading. It is the addition of cement that reduces the insulating value of the resulting mix. For example vermicrete and perlcrete are the same in insulating value although perlite has a lower thermal conductivity than vermiculite. If you want a stronger mix add more cement and some sand, but you reduce the insulating value. Less cement gives you lower strength and better insulation. I use 5:1 vermiculite, cement for a layer that needs to support weight and a 10:1 for dome insulation. I think a 3:1 is too much cement and won't insulate well.