Perlite is used widely as a loose-fill insulation in masonry construction. In this application, perlite is poured into the cavities of concrete block, where it completely fills all cores, crevices, mortar areas, and ear holes. A nominal R-value of 2.7 per inch typically is used for calculation purposes; however, a range of 2.5 to 4.0 has been achieved. Expanded perlite can be manufactured to weigh as little as 2 lb/ft3, making it adaptable for numerous applications. In addition to providing thermal insulation, perlite is fire-resistant, has low water absorption, reduces noise transmission, and is resistant to rot, vermin, and termites. Perlite loose-fill insulation is packaged in bags and must be poured into place. It is not suitable for blow-in installation methods. It is best used for attics and is reasonably well suited for walls.