#1  
Old 06-27-2011, 06:47 AM
Laborer
 
Join Date: Jun 2011
Location: Westborough, MA
Posts: 59
Default I can only pick one

So, I am in Mass. I have luckily been able to find a supplier for Durablanket and Duraboard. I also have a wholesale supplier of perlite and vermiculite.

Blanket and board together are too cost prohibitive. I could use all perlite/vermiculite, but I would like to get the most for my money.

The question is what would you choose to do:

1. 4.5" Insulating concrete using perlite and 3" of durablanket insulation around the dome

2. 2" Insulating duraboard under the oven and loose fill perlite around the dome to 4-6"

Or any other suggestions.
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  #2  
Old 06-27-2011, 08:52 AM
Faith In Virginia's Avatar
Master Builder
 
Join Date: Oct 2010
Location: Virginia
Posts: 720
Default Re: I can only pick one

I used 3.5 vermiculite/Portland at a 5 to 1 ratio and 4 inches of ceramic blanket add I am more then satisfied with my oven's heat retention. In hind site I do wish I went to 4.5" but that is before I started with this place. So in my do-over land that is the only change I would make.

Hope that helps, Faith
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Old 06-27-2011, 11:39 AM
Laborer
 
Join Date: Jun 2011
Location: Westborough, MA
Posts: 59
Default Re: I can only pick one

Logic would seem to indicate that the best place to spend the money is on the dome as heat rises. However, I could see an argument that the floor could become a heat sink also and wick heat away from the cooking surface.

Thanks for the feedback Faith

-Jake
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Old 06-27-2011, 03:14 PM
Faith In Virginia's Avatar
Master Builder
 
Join Date: Oct 2010
Location: Virginia
Posts: 720
Default Re: I can only pick one

Not really Jake, Heat rises in an air environment for the most part. In solid surfaces I see heat more as a migration. The heat will migrate to the cool so your heat loss is almost equal floor to dome. So the mantra around here is "insulate, insulate, insulate". Your on the right track with either of your choices.
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Old 06-27-2011, 06:18 PM
Laborer
 
Join Date: Nov 2009
Location: Lancaster Co., Pa.
Posts: 55
Default Re: I can only pick one

I had the same problem when I built my Pompeii. I went with 4" of vermicrete under the hearth and 3" ceramic blanket over the dome, plus another 3" of vermicrete over the blanket. My oven stays hot enough to cook something for 3-4 days, at least.
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  #6  
Old 07-31-2011, 03:19 PM
Apprentice
 
Join Date: Sep 2010
Location: Easley, SC
Posts: 114
Default Re: I can only pick one

Jake,
I'm in a similar situation to you. I'm trying to keep my costs down. As much as I'd like to use the Duraboard 2" and Durablanket 3" it's going to cost me $450 (assuming I drive down to Atlanta and pick it up (4h round trip).
I figure 20 sf Duraboard at $11/sf (1@2x4 + 2@2x3 ) + 3 rolls of Durablanket (S Blanket 2300) at $70 for 50sf + sales tax.
The portland cement and vermiculite is my likely choice for the bottom at 5" thick. The woman on the phone at the Feed&Seed store has vermulite for $15/bag for a 'big' bag. I'll need to go see it - lol.
I'm having a hard time estimating how much I'll need as the vermiculite/perlite will likely shrink some.

So what did you finally choose?

Jeff
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Old 07-31-2011, 06:44 PM
Laborer
 
Join Date: Jun 2011
Location: Westborough, MA
Posts: 59
Default Re: I can only pick one

Hi Jeff,
So, I am going with a fairly thick insulating layer of vermiculite concrete (5 1/2" aka 2x6 frame). Then I was able to locally find durablanket 6# 1"x2'x50' for $75 a roll. I was able to get 4 cuft("big") bags of vermiculite for about $13 each. Make sure you get as corse as you can, a lot of garden vermiculite is fine. Pictures of what the bags I got look like in this thread:
http://www.fornobravo.com/forum/f21/...1-a-16285.html (Jake's In Mass (Started July 3, 2011))

I would say since the vermiculite is not too expensive get slightly more than you think you need, bump up to the next bag if you are on the edge and return it if you don't use it, or start a veggie garden with it next year.

So, what I have:
2 x 4cuft vermiculite super coarse at $13 each(dad grows flowers for a living)
3 x 1"x2'x50' 6lb durablanket at $75 each

Not too bad price wise. The local source for the blanket also has the board, but it is crazy expensive.
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