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Old 06-23-2011, 02:27 PM
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Default Yet another insulation question

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Old 06-23-2011, 03:34 PM
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Default Re: Yet another insulation question

They're both the same. Same insulating properties, same manufacturing processes (they are expanded minerals - popped in heat like popcorn).

Perlite is white: it makes a good visual marker when your gray portland is evenly distributed.

Vermiculite is said to be less dusty.

Neither one of these is a deal killer in my book.
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Old 06-23-2011, 03:54 PM
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Default Re: Yet another insulation question

I used half perlite and half vermiculite. I found this a bit easier to work with that straight vermiculite, particularly when forming/screeding the dome layer.
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Old 06-23-2011, 09:41 PM
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Default Re: Yet another insulation question

Quote:
Originally Posted by dmun View Post
They're both the same. Same insulating properties, same manufacturing processes
Hi dmun,

Do Perlite and Vermiculite actually have the same insulating properties?

Forgive the question, I'm just a natural-born-fool from Gippsland, but the data I have indicates that Perlite has a thermal conductivity almost half that of Vermiculite (0.031W/m.K for Perlite, 0.058W/m.K for Vermiculite).
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Old 06-23-2011, 11:05 PM
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Default Re: Yet another insulation question

I suspect there are a lot of variables involved with Perlite/Vermiculite/Portland insulation value. Grain size, ratio of Portland, how long it's mixed, etc.

For our purposes (insulating under an oven floor), 4" of either material will give you satisfactory results. Is one better than another in a laboratory? Probably. Are you going to notice a difference in your oven. I seriously doubt it.

It's like comparing flat panel TV's at Walmart. One might look a little better in the store, but either will look great in your living room.
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Old 06-26-2011, 10:03 AM
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Default Re: Yet another insulation question

Thank you Ken for that analysis. For our needs, there is no reason to re-invent the wheel.
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Old 06-26-2011, 01:06 PM
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Default Re: Yet another insulation question

Ben,
Last time I checked thermal conductivity it said perlite was just a slightly better insulator than vermiculite, not double. I prefer to use vermiculite because it seems to mix up better and hasn't got that irritating dust that perlite seems to have. The perlite I use tends to abrade more than the vermiculite on mixing and you end up losing a bit of volume. You are not meant to mix either of them for too long, i think for this reason. Vermiculite also seems to coat with the cement a bit better, the grains of perlite are rounder and smoother and it doesn't seem to stick as well. Sorry for the extended answer. If I were making a choice between the two I'd take vermiculite.

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Old 06-26-2011, 06:29 PM
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Default Re: Yet another insulation question

For under floor insulation, you cant beat calcium aluminate board, end of story.
OOPs that should be Cal. Silicate board.

Last edited by Johnny the oven man; 06-26-2011 at 09:27 PM.
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Old 06-26-2011, 06:50 PM
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Default Re: Yet another insulation question

Thanks for your response Ken and David, and don't worry, I like extended answers!
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