Uses for Scoria (Lava Rock)
hudson_valley_gregg
| Posted in Green Building Techniques on
Considering utilizing a 5″ layer of scoria (or some other natural material) as an insulative layer underneath a 5″ layer of gravel as part of an earthen floor system. The scoria would provide the insulative value others seek to realize in poly sheets or the like. Seem like a sound construct? Thanks.
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No idea what scoria is, but poly sheets are used to control moisture rather than to insulate.
Scoria is not an insulator. It might be a bit better than compacted soil, but not by a lot. A 5" layer of it might be R-1. The incremental increase over 5" of soil would be about R-0.5. Definitely not worth the cost or effort.
Thanks for the responses, CL & TL. Got the convo started. Foam boards is more what I meant to write (as opposed to poly sheets) regarding insulation, and it's important to note the consideration of moisture barriers. I'm seeing skepticism on the scoria as insulator front, and other solid fossil-free insulative options might include...
Scoria is basically just porous stone. One might think that the air pockets give it insulation properties, and they probably do, just not a lot. Think of the holes as the insulation, and the lattice structure of the rock as a thermal bridge. Just like a cinder block may insulate better than solid concrete, no one would purposely use cinder block as insulation.
Some people have claimed scoria has significant r-value for a long time, but no one's ever demonstrated it, and it's not like it would be especially difficult to test.
Most builders in my neck of the woods (Hudson Valley) used tons of red brick as insulation in the late 1800s - much better than nothing. As with most naturally occurring phenomena, paid scientists driven to execute long-term testing are scarce since it's not proprietary petrol-based product?
You could test it yourself with minimal tools. There's really no reason to suspect it's going to turn out to be a good insulator, aside from the desire that it be so.
As for the scientist conspiracy theory, you could make the same argument about straw bales or sheep wool, and yet we know those are good insulators and have accepted R-values.
Red bricks certainly are better than nothing. But in the case of a floor on the ground, it isn't nothing you're starting with, it's the ground itself.
Check out Glavel: https://www.glavel.com/
There is also Perlite that can be used. A local design-builder has used it while still in the bag. Just stacks it horizontally.
One can use mineral wool below grade, but it does compress so check with your engineer about loads.
Josh
Scoria R value is about R1/inch, which is nowhere near foam but is about 10x (this varies widely) better than soil.
Do you have a source for the R-1 per inch value?
Do you have a low-cost source of it? 10" of it might give you R-10 which might be acceptable in your climate zone.