Perlite Board Product description
As discussed in Chap. 7, perlite is a granular-type insulation made from a naturally occurring silicous rock quarried mainly in the western United States. Perlite is different from other volcanic glasses because when the crushed ore is heated to a suitable point in its softening range, it expands from 4 to 20 times its original volume.
Used for low-slope roofing systems, perlite insulation is manufactured as a rigid board that is composed of these expanded volcanic minerals combined with organic fibers and binders. An asphalt emulsion is used to treat the top surface to inhibit the absorption of bitumens. Perlite is compatible with bitumens and other adhesives, fire-resistant, dimensionally stable, and compatible with other roofing materials. The board will withstand impact, but care must be taken when handling the boards because they can break easily. The thermal resistance of the insulation is stable, but it has a relatively low R-value. Typically, perlite is not used with ballasted, loose-laid membranes because the board will readily absorb moisture.4