Posted By Liebler on 01 Oct 2012 11:40 AM I didn't find the water retention data ICF mentioned but I did find this:"Perlite loose-fill insulation is an inert volcanic glass expanded by heating to 1600° F (850° C) andtreated with a non-flammable silicone to ensure against water retention. The resulting granular productis lightweight with countless tiny, sealed air cells which account for its excellent thermal performance.The characteristics of perlite loose-fill insulation provide many additional benefits including:- Perlite loose-fill insulation is free-flowing and will uniformly and completely fill all cores and voidsin masonry wall units.- Perlite loose-fill insulation is inorganic and is rot, vermin and termite resistant.- Perlite loose-fill insulation is non-combustible with a fusion point of approximately 2300° F(1260° C), while EPS products are combustible.- Perlite loose-fill insulation improves the fire rating of an 8 inch concrete block from 2 hours to 4hours- a 100% improvement!- Perlite loose-fill insulation is non-settling and supports its own weight in masonry wall cavitiesand masonry block cores.- Perlite loose-fill insulation may be easily installed without special training or equipment." So there may be good reason to being specific in ordering perlite, making sure to get the loose fill insulation grade or type.I wish I could find the reference as it is my understanding that perlite does not aBsorb any water instead it aDsorbs water in soils by creating soil pores. FWI aDsorb is to hold water on the outside of a particle while aBsorb is to hold water internally.
Posted By Liebler on 04 Oct 2012 04:56 PM Whirnot, Here is the page of the perlite institute on underfloor loose perlite that shows r values from 3 to 3.7/in. for underfloor use. http://www.perlite.org/product_guides/21%20perlite%20for%20underfloor.pdf