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  #31  
Old 03-06-2013, 08:56 AM
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Default Re: What do you have for Insulation

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Originally Posted by mrchipster View Post
Perlcrete will hold up but is not the best insulator directly against the Firebrick so I would recommend 1" - 2" of ceramic board next to the Firebrick

Foamglas is very brittle and hard to lay firebrick directly on so a layer of 1-2 inches of creamic board would be recommended next to the Floor brick.

That is how the oven I am assisting with right now is being built.

Floor Brick
1" Ceramic Board
4" Foamglas

Stacked as above

My oven is

Floor Brick
2" ceramic FB Board
2.5" 7/1 Vermicrete

I wish I had more insulation under the floor.....

Chip
I think I'm going to stay away from the Foamglas. What would you change on yours? Would you have had 4" of FB board and 2.5 of the 7/1 Vermicrete or would you have kept the 2" of FB and increased the Vermicrete layer. Also what's better perlcrete or vermicrete? Thanks
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  #32  
Old 03-06-2013, 09:11 AM
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Default Re: What do you have for Insulation

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I think I'm going to stay away from the Foamglas. What would you change on yours? Would you have had 4" of FB board and 2.5 of the 7/1 Vermicrete or would you have kept the 2" of FB and increased the Vermicrete layer. Also what's better perlcrete or vermicrete? Thanks
I have my vermicrete contained in a concrete cutout so it is fully supported on the sides. This is not a recommended approach if you are building an igloo style as you can create a bathtub type effect and trap water, but I have a nice house over mine,

I would have gone with 4 inches of vermicrete or perlcrete at a 11/1 ratio to increase the insulating value and then 2 inches of ceramic on top of that. Because the way I built my hearth slab fully contains the vermicrete I could have had the very high ratio perlite or vermicrete without any structural issues if not contained that ratio is quite weak at the edges.

The reason we are using foamglas on this next project is that I got some real cheap and it is also a great product.

I guess I would use the Foamglas if I had not given it to the person who I am helping,

From what I have read Perlcrete is slightly better insulation value
Chip
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  #33  
Old 03-06-2013, 09:14 AM
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Default Re: What do you have for Insulation

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Originally Posted by mrchipster View Post
I have my vermicrete contained in a concrete cutout so it is fully supported on the sides. This is not a recommended approach if you are building an igloo style as you can create a bathtub type effect and trap water, but I have a nice house over mine,

I would have gone with 4 inches of vermicrete or perlcrete at a 11/1 ratio to increase the insulating value and then 2 inches of ceramic on top of that. Because the way I built my hearth slab fully contains the vermicrete I could have had the very high ratio perlite or vermicrete without any structural issues if not contained that ratio is quite weak at the edges.

The reason we are using foamglas on this next project is that I got some real cheap and it is also a great product.

I guess I would use the Foamglas if I had not given it to the person who I am helping,

From what I have read Perlcrete is slightly better insulation value
Chip
Is it because of cost that most people don't just put 4" of ceramic board down under their oven floor? Seems like the easiest option, but not the cheapest.
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  #34  
Old 03-06-2013, 09:31 AM
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Default Re: What do you have for Insulation

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Is it because of cost that most people don't just put 4" of ceramic board down under their oven floor? Seems like the easiest option, but not the cheapest.
Agree, Cost is high on the ceramic board. and not a huge return after you get outside of 2 inches unless you cannot afford the extra thickness,

I see heat bleeding into my structure with the current insulation that is why i wish I had more and a higher ratio in the vermicrete. or foamglas would have been good also.

Chip
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  #35  
Old 03-06-2013, 09:39 AM
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Default Re: What do you have for Insulation

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Agree, Cost is high on the ceramic board. and not a huge return after you get outside of 2 inches unless you cannot afford the extra thickness,

I see heat bleeding into my structure with the current insulation that is why i wish I had more and a higher ratio in the vermicrete. or foamglas would have been good also.

Chip
I would have thought doubling the ceramic board insulation might have a large return on heat preservation? Why not with this board? Would a 7/1 vermicrete mix be stable enough to not be enclosed by regular concrete? The FB plans show the vermicrete extending to the edge of the slab with a firebrick island in the center. I'ld be worried about screwing metal studs into the vermicrete. I also don't like the idea of building an island of vermicrete with concrete around it. Worried about water like you although with a full enclosure I don't see how any water could get in there.
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  #36  
Old 03-06-2013, 11:08 AM
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Default Re: What do you have for Insulation

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I would have thought doubling the ceramic board insulation might have a large return on heat preservation? Why not with this board? Would a 7/1 vermicrete mix be stable enough to not be enclosed by regular concrete? The FB plans show the vermicrete extending to the edge of the slab with a firebrick island in the center. I'ld be worried about screwing metal studs into the vermicrete. I also don't like the idea of building an island of vermicrete with concrete around it. Worried about water like you although with a full enclosure I don't see how any water could get in there.
7/1 is plenty stable not enclosed.

4 inches of ceramic would be great except for the extra money. but i think that would be an ideal setup if you can afford it,

I agree on not extending vermicrete layer to the outer edges I would much rather mount direct to real concrete and that way you could embed anchors in the concrete while wet, and just bolt the studs down. or drill in anchors and put in screws.

You should still have the vermicrete and board extend beyond your brick an inch or so so as to not wick heat away from the oven, I would elect for 2 inches as sometimes the placement of your oven will vary slightly over original intended location that way you have a safe zone,

Chip

Last edited by mrchipster; 03-06-2013 at 11:10 AM.
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  #37  
Old 03-06-2013, 11:43 AM
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Default Re: What do you have for Insulation

Just my opinion, but I think 2 inches of the CF board + x inches of a less expensive material is a good way to go. The CF board will do most of the work, so under that you don't need as expensive a material because the temps won't be as extreme through 2" of CF as they are under the floor. Lots of builders pour vermicrete and then put CF board on top of that and have good performance.

One thing to consider is how high your cooking surface will be with your final insulation. I am not sure if you have poured your base yet, so you may more freedom with that. I know that in my case my base was there at 40", so I could only put 3" of insulation under the oven (2" of CF + 1" of a 1900 degree board that was only $10 a sheet). For a relatively mild climate like seattle, that is plenty - but in maine you may want to better isolate your oven from the slab - Chip has the experience there.
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Last edited by deejayoh; 03-06-2013 at 12:08 PM.
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  #38  
Old 03-11-2013, 04:15 PM
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Default Re: What do you have for Insulation

I found a place that is local that sells pre fabricated ovens and they place Skamol under their ovens. It's a 3" thick board. Here is a link to the board:

http://www.skamol.com/media/1[calcium_silicate_slabs]A4.pdf

You might have to copy and paste the link to your url for some reason.

Is this a good one to use? If so this will save me a lot of time and money on shipping !
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  #39  
Old 03-11-2013, 04:52 PM
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Default Re: What do you have for Insulation

that's Cal-sil. It should work just fine. I have that for my lower layer - but plenty of people have used it by itself.

There are some threads here on Cal-sil vs. Ceramic Fiber board if you do some searching. Cal-sil is certainly quite a bit cheaper!

here is the link fixed
Skamol
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Last edited by deejayoh; 03-11-2013 at 04:54 PM.
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  #40  
Old 03-11-2013, 04:55 PM
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Default Re: What do you have for Insulation

They sell it 3" thick. I was thinking of using 3" of that and 4" of vermicrete below it.
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