Why not insulating firebricks for hearth insulation?

[GianniFocaccia]

Re: Why not insulating firebricks for hearth insulation?

I'd spring for the board for two reasons: $100 for your entire oven to be insulated with 2" IB is really cost-effective, and the board does make a nice platform to lay your oven floor on. Besides, there are a great many ovens out there that have been built on 2" of IB.

I used seven 1x3' boards for my 42" oven which came out to a 53 1/2" diagonal.

[dmun]

Re: Why not insulating firebricks for hearth insulation?

I used two and a half inch of insblock19 directly on top of my support slab: I laid the blocks down on the slab when it was wet. The surface was flat enough to put my brick floor right down on them without any leveling medium. My support slab never warms up even with a big pizza bake, and is only slightly warm the next day. I recommend it.

[kebwi]

Re: Why not insulating firebricks for hearth insulation?

All right, I'm sold. InsBlock 19 it is! Still unsure whether to go local or mail. I was originally thinking of getting the large box-sets from Northwest Iron Works and using the extra pieces to make the door, but some discussions on FB have put me off that idea now, the thinking being that InsBlock shouldn't be anywhere near the interior of an oven with food in it, so now I'm not sure what I would do with the extra pieces.

Seattle Pottery Supply:
36"x12"x1"-1: $10.65 + 9.5% sales tax = $11.66 = $46.64/ft^3

Northwest Iron Works:
36"x12"x1"-16: $92 + $43.78 shipping = $135.78 = $33.94/ft^3
36"x12"x1.5"-10: $90.50 + $43.78 shipping = $134.28 = $35.81/ft^3
36"x12"x2"-8: $92 + $43.78 shipping = $135.78 = $33.94/ft^3
36"x12"x3"-5: $94 + $43.78 shipping = $137.78 = $36.74/ft^3

Five 12"x36" pieces only works if I leave some of the entry way uncovered by board. Less an issue about insulation, there is the issue of augmenting the remaining uncovered area of the entryway with some other material (small patch of vermicrete?) such that I get a perfectly level surface on which to lay the bricks...so the 3" option listed above is probably less ideal for that reason.

Well, I'll think about it. Maybe eight pieces of 2" makes the most sense. I can use six pieces for the floor and have two more pieces for whatever comes along, maybe some sort of sealed door, or maybe just dump it on Craigslist.

Thanks for the advice.

BTW, for any other folks in Seattle, Seattle Pottery Supply's e-catalog is out of date. It lists items they don't carry and their prices are higher than quoted in the catalog for the remaining items.

[Andrew Beal]

Re: Why not insulating firebricks for hearth insulation?

There is a supplier in New Zealand that sells the porous type insulating fire bricks made from pyrolite for under half the cost of traditional alumina firebricks. The supplier says they can take the heat. He even has thin bricks that look like pavers. They are the type of bricks that they put in woodburner type home fireplaces. Can I use these bricks for the Hearth or even the dome. What would be the dissadvantages?

Here is the link:
BRICKS (Fire) #Other Sizes Also Available# for sale - TradeMe.co.nz - New Zealand

[dmun]

Re: Why not insulating firebricks for hearth insulation?

Of course insulating firebricks will "take the heat". They are used in pottery kilns, and are made to be heat resistant. The question is, what will they do with it...

The brick in a wood fired oven absorbs the heat and reflects it back to the cooking surface. It's what cooks the food. The insulation around the brick helps hold the heat in the brick, and concentrate it. An insulating brick oven would get very hot above the fire, and nowhere else.

[Neil2]

Re: Why not insulating firebricks for hearth insulation?

I used a few in the area around the oven opening. I got them cheap (free) from a local potter who was breaking up a kiln.

Vermiculete is plenty strong enough, way cheaper, pours into the shape you want and has equal if not better insulating values.