Pouring loose-fill granular materials into block cores is a simple way to add insulation value to masonry walls. Two types of material meet Brick Institute of America (BIA) design criteria for loose-fill granular insulation: perlite and vermiculite. A third material is expanded polystyrene (EPS) beads. Each of these materials can add appreciably to the wall's R value, without increasing wall thickness, covering the face of the masonry, or significantly complicating construction. PERLITE AND VERMICULITE PROPERTIES Both perlite and vermiculite are naturally occurring mineral products. Perlite is a siliceous volcanic rock. Vermiculite is a form of mica, which also is expanded by heat treatment for use as insulation. Both perlite and vermiculite are treated with silicone or other agents during processing to make them more water repellent. EXPANDED POLYSTYRENE PROPERTIES EPS beads generally are produced by manufacturers who regrind scrap pieces of molded EPS board. The plastic beads also are used to stuff toys and bean-bag chairs. INSTALLATION PROCEDURES Loose-fill insulation is poured from the bag directly into the block cores, or into a hopper that rests on and slides along the top of the wall. Because perlite and vermiculite are free-flowing, these materials fill all voids in the cores without tamping or rodding.