Insulation bricks

[ricocamus]

Originally Posted by dmun

Sand and Salt are traditional insulators, but they aren't very efficient, because they don't trap much air. Aren't the Philippines volcanic? Can you get some kind of light weight volcanic rock like pumice or tufa? That would be almost as good as vermiculite.

Pumice should be relatively easy to get. Pardon the ignorance, but would you crush the pumice to mix it up in the concrete for the hearth? Or would you the stones? I guess it depends on the size of the pumice stones.

I'd be really interested to hear what you think. At this point, finding vermiculite is one of my materials issues.