#11  
Old 08-14-2013, 06:13 PM
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Default Re: Is the home depot vermiculite good?

Mix by volume, meaning you can use any size bucket or pail.

If you have a ratio of 1:6 that means......

1 part - Type I/II portland cement ( not pre-mix containing sand or masonry cement)

6 parts perlite or vermiculite.
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  #12  
Old 08-14-2013, 06:38 PM
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Default Re: Is the home depot vermiculite good?

Stonecutter, I will differ with you on the fine perlite not being as effective as coarse. It is all about surface area and the smaller the grain the greater the surface area for a given volume. It makes it harder to mix well, but it also provides more insulation value.
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  #13  
Old 08-14-2013, 06:48 PM
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Default Re: Is the home depot vermiculite good?

I don't see how it could....I feel the larger air spaces created by the larger particles make for better insulation.
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  #14  
Old 08-14-2013, 07:49 PM
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Default Re: Is the home depot vermiculite good?

Follow it to it's logical conclusion: The BEST insulation would be just an air space by that logic. This is obviously not true. The best insulation is that which provides the most surface area, or alternatively, has no air at all (a vacuum). Observe the size of the granules of an open celled foam and a closed cell foam, then note the R values of each. The difference is surface area.
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Old 08-14-2013, 07:49 PM
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Default Re: Is the home depot vermiculite good?

Quote:
Originally Posted by stonecutter View Post
I don't see how it could....I feel the larger air spaces created by the larger particles make for better insulation.
I should think that in theory the difference in grain size would be negligible, unless the stuff was ground down to powder. Eg a bucket full of large marbles has the same density as a bucket full of small marbles. The spaces between them are smaller, but but there are more of them. I've found that the fine grade of vermiculite requires more water (because of the larger amount of surface area exposed presumably). The fine vermiculite makes a more workable mix, but then because it takes up more water then there is more to eliminate and I should think that it would dry slower than the course stuff. I'd love to see some tests that show a difference in insulating capacity between fine and course. I suspect that the difference if any would be very small.

I've used both course and fine and while I haven't weighed the bags, did not notice any difference in weight (density)

Last edited by david s; 08-14-2013 at 07:54 PM.
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Old 08-14-2013, 07:52 PM
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Default Re: Is the home depot vermiculite good?

The difference is not small, David, it is almost double for open VS closed cell foams.
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  #17  
Old 08-14-2013, 08:25 PM
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Default Re: Is the home depot vermiculite good?

You can't compare R values of foam to perlite. I could easily use that surface area reasoning to say a cavity filled with sand is a better insulator than course gravel...and I doubt that.

What I'm saying is that R-vaule is determined not just by size of the material but what the material is made of. A perlcrete slab made with fine perlite is closer to a solid mass than a slab that is made with course perlite.....period. So in my mind, fine grains will not insulate as well as course grains, because of the conductivity of the cement in the slab.

I find it impossible to see how fine grade perlite will have a higher R-value because of this. Air is a poor heat conductor compared to solid material.
However, I am not so stubborn that I can't see the possibility that fine grade may have an edge over course...simply by functioning by trapping more heat by not having the larger cavities.

Conversely, do the finer particles conduct and transmit more heat because they are more densely packed? This is a possibility too.

I have a feeling we are splitting hairs. But I can guarantee you one thing....course perlite is not as dusty to work with.
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Last edited by stonecutter; 08-16-2013 at 05:48 AM.
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  #18  
Old 08-14-2013, 08:37 PM
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Default Re: Is the home depot vermiculite good?

Quote:
1 part - Type I/II portland cement ( not pre-mix containing sand or masonry cement)

6 parts perlite or vermiculite.
I will do that then, but what confused me was the getting started thread, which says concrete mix in the drawing.
http://www.fornobravo.com/forum/f6/h...sophy-693.html (Hearth Design Philosophy)
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  #19  
Old 08-14-2013, 08:46 PM
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Default Re: Is the home depot vermiculite good?

Quote:
You can't compare R values of foam to perlite. I could easily use that surface area reasoning to say a cavity filled with sand is a better insulator than course gravel...and I doubt that.
I don't have lots of experience but, I've seen hearts in South America composed by broken glass and salt, or even beer bottles .

Last edited by martin_80x; 08-14-2013 at 08:49 PM.
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  #20  
Old 08-14-2013, 08:50 PM
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Default Re: Is the home depot vermiculite good?

Quote:
Originally Posted by martin_80x View Post
I've seen hearts in South America composed by broken glass and salt, or even beer bottles .
I've seen that too, along with clay earth mixed with sawdust.


We do this occasionally...and I love it. A good discussion ( without getting bent out of shape) will just make you a better builder....and a better forum user.
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