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  #11  
Old 03-17-2008, 10:52 AM
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Join Date: Dec 2007
Location: Vermont
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Default Re: Insulation Efficiency

Thanks Jim. Not having seen the product, I was thinking it was maybe less dense than it actually is.
My inclination is to use a box enclosure around the oven. Have you ever used unfaced fiberglass at the point you would use vermiculite fill (after a hi-temp blanket)?
I think it has better insulating properties & is certainly easy to get.

Ted
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  #12  
Old 03-18-2008, 06:29 AM
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Location: Prince Albert, Ontario, Canada
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Default Re: Insulation Efficiency

Ted,

I have no experience with using fiberglass insulation around an oven. What I normally do is use three inches (five at the apex) of insulating blanket, then a further three (and five) of castable refractory insulator. The product I use for this last is called Matrilite 18, although you could use vermiculite/cement at a ratio of 5:1. After that, you could fill with dry vermic, but I really don't think it's necessary, even in my climate.

Jim
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  #13  
Old 04-08-2008, 06:15 PM
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Default Re: Insulation Efficiency

I used fibreglass insulation on my first oven. It works ok but compresses easily which made it really hard to get the outer spherical form right. I ended up with only half the intended insulation thickness. I would only use vermiculite again. There is a cloud over the safety of ceramic fibre (carcinogen)
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  #14  
Old 10-23-2008, 05:52 AM
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Location: doylestown pa
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Default Re: Insulation Efficiency

1" insulfrax, 2-4" vermiculite then 9" fiberglas seems to be working real well for me-- no temps taken on exterior of insulation, but if I put the oven "to sleep" at 400, it's 300+ in the morning. under hearth slab is 4" of vermiculite concrete (slab per Alan Scott method, pompeii dome oven per Forno). I may add some fiberglas underneath this winter. Seems to me the key is not to have 1,000 degree brick against the inexpensive fiberglas. But fiberglas is sure a great value compared to alternatives.
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  #15  
Old 03-15-2009, 02:34 PM
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Default Re: Insulation Efficiency

Is it possible to over insulate ?
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  #16  
Old 06-14-2009, 01:20 PM
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Location: Northridge, CA
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Default Re: Insulation Efficiency

RE: How much slab (cooking floor) insulation:

I have ONLY the 2" of FB Board sitting directly on my 4" concrete slab that I poured onto Durock cement board (I did not use plywood, placed the cement board and just left it there after the 4" conc. pour) and last night I had 800 and 900 deg pizza fires for 4-5 hours. The infrared thermometer said the cement board under my oven was 80 deg and hit 91 deg at the hottest period. This morning I still have 500 degrees in the oven and 80 deg on the cement slab underneath. I think that is very low heat loss.

Use these numbers for comparissons on the efficiency of FB board 2" vs (or in addition to) vermiculite - concrete insulation under the oven.
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  #17  
Old 06-14-2009, 04:07 PM
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Default Re: Insulation Efficiency

Quote:
Is it possible to over insulate ?
If you use more insulation than is needed to keep the outside of your enclosure at room temperature, you're wasting money, but there is no particular harm. You can't go wrong with the recommendations in the plan.
Quote:
But fiberglas is sure a great value compared to alternatives.
Be sure to keep domestic fiberglass insulation away from anything hotter than you can touch: It has an organic binder that breaks down (and smells bad) when hot.
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  #18  
Old 07-04-2009, 02:10 AM
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Default Re: Insulation Efficiency

Has anybody use rockwool? I'm insulating at the same time as I'm building the dome, packing loose rockwool in a 1" space I leave in the wet vermiculite mix next to the dome. The final shape is unimportant as the whole thing will be enclosed. If you're wondering why I'm using rockwool, I have a large bag of it left over from a different job and it seems a shame not to use it.
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  #19  
Old 07-04-2009, 05:26 AM
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Default Re: Insulation Efficiency

"Rockwool" is a term we don't use in the US. If it's domestic insulation, like fiberglass, it may have organic binders that will burn and stink at the right-next-to-the-dome temperatures. Before you get too far, heat up your kitchen oven to 550 degrees f. (288 degrees c.) put a chunk of the rockwool in, and see if it stinks up the place.

If it's a refractory insulation, you should be good to go.
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  #20  
Old 08-17-2009, 08:29 PM
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Default Re: Insulation Efficiency

Two questions....

Can you just pour vermiculite and fill in around the dome without an insulating blanket?

Hardware stores sell insulating blankets to wrap around hot water heaters, heat pipes, etc. Can you use that material?
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