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wotavidone 06-23-2011 02:27 PM

Yet another insulation question
 
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dmun 06-23-2011 03:34 PM

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.

Neil2 06-23-2011 03:54 PM

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.

benguilford 06-23-2011 09:41 PM

Re: Yet another insulation question
 
Quote:

Originally Posted by dmun (Post 115683)
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).

Ken524 06-23-2011 11:05 PM

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.

lt4827 06-26-2011 10:03 AM

Re: Yet another insulation question
 
Thank you Ken for that analysis. For our needs, there is no reason to re-invent the wheel.

david s 06-26-2011 01:06 PM

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.

Johnny the oven man 06-26-2011 06:29 PM

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.

benguilford 06-26-2011 06:50 PM

Re: Yet another insulation question
 
Thanks for your response Ken and David, and don't worry, I like extended answers! :)


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