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Old 08-21-2008, 03:24 AM
ross's Avatar
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Default silver foil - insulation layer

hi all

About to start the insulation on my dome....after a few running repairs this morning

Is it best to put silver foil on before the blanket and then the vermiculite outer layer

or

blanket - silver foil - vermiculite..

or

silver foil - blanket - silver foil - vermiculite...

also the vermiculite outer mix is 5 -1 cement is it ok to add a little sand to the mix

cheers
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Old 08-21-2008, 09:34 AM
dmun's Avatar
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Default Re: silver foil - insulation layer

With silver this morning at $13.75 an ounce, I'd skip the silver foil. In fact, I'd skip any foil whatever. The most common, aluminum, will be corroded instantly by the portland cement. It really doesn't have any function.
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Old 08-21-2008, 09:53 AM
Jed Jed is offline
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Default Re: silver foil - insulation layer

Quote:
Originally Posted by ross View Post
hi all

also the vermiculite outer mix is 5 -1 cement is it ok to add a little sand to the mix

cheers
Hey Ross,


The foil really doesn't add any value to the system with the blanket insulation. And the Portland does corrode the foil in short order.

And the sand in the vermiculite mix will not add any value.. the idea is to get as much 'insulation' as possible, and that comes from the vermiculite. You use the Portland (cement) to hold the vermiculite together. The less Portland you use the better the insulation value; there is one guy in this forum who was getting as much as a 12:1 mix. As some point you need the Portland to provide the strength to keep the whole thing together and you can't go wrong with the 5:1 mix.

JED
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Old 08-21-2008, 09:59 AM
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Default Re: silver foil - insulation layer

Don't add sand the the vermiculite cement mix. The idea is to just coat the vermiculite with cement as loose as you can. The mix creates tiny pockets of air- those pockets insulate (think of a double pane window, thin layer of air in between the glass). If you add sand you fill in the air pockets and lose insulation.
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