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During my initial research I found the super expensive bags of vermiculite and perlite at Lowes. They were in transparent bags so I could see what they looked like and I remember them being gray and rather large in granularity, several mm if I recall.
Then I found a super cheap source of perlite at a masonry store and this morning bought three 4 ft^3 bags without a second thought (I anticipate using five or six eventually). This stuff was much whiter, ivory perhaps. More to the point, it is much finer than the stuff I saw at Lowes. It looks like laundry detergent, grain size of half a mm perhaps? My concern is that smaller grains might pack tighter, leaving less "fluff", less air, and weaker insulation.
Are there different types of perlite and did I get the wrong kind? The bag even lists insulation as a possible application, so that gives me hope.
My final decision for perlite over vermiculite was based on the facts that it is the cheaper of the two and reportedly has a slightly higher insulative R value.
Shouldn't I want something with large grains so it will pack loose with large air pockets? Is this a vermiculite/perlite distinction (which implies that I am not remembering the appearance of the perlite at Lowes accurately) or does perlite come in different grain sizes...and would I be correct in assuming I want the largest grains possible for the loosest fill?
BTW, my application will most likely be concrete, not loose fill, since I'm doing a dome, not an enclosure, although I am considering the approach of a rebar-chicken-wire stucco dome with a dead space around the brick dome and filling it with loose fill as opposed to concrete, haven't decided yet. Obviously, the hearth is concrete either way.
Thanks a lot.
Then I found a super cheap source of perlite at a masonry store and this morning bought three 4 ft^3 bags without a second thought (I anticipate using five or six eventually). This stuff was much whiter, ivory perhaps. More to the point, it is much finer than the stuff I saw at Lowes. It looks like laundry detergent, grain size of half a mm perhaps? My concern is that smaller grains might pack tighter, leaving less "fluff", less air, and weaker insulation.
Are there different types of perlite and did I get the wrong kind? The bag even lists insulation as a possible application, so that gives me hope.
My final decision for perlite over vermiculite was based on the facts that it is the cheaper of the two and reportedly has a slightly higher insulative R value.
Shouldn't I want something with large grains so it will pack loose with large air pockets? Is this a vermiculite/perlite distinction (which implies that I am not remembering the appearance of the perlite at Lowes accurately) or does perlite come in different grain sizes...and would I be correct in assuming I want the largest grains possible for the loosest fill?
BTW, my application will most likely be concrete, not loose fill, since I'm doing a dome, not an enclosure, although I am considering the approach of a rebar-chicken-wire stucco dome with a dead space around the brick dome and filling it with loose fill as opposed to concrete, haven't decided yet. Obviously, the hearth is concrete either way.
Thanks a lot.
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