Loose-fill insulation (Figure 3-9) is available in granular, fibrous, or powdered form and is sold in bulk, usually in bags (Table 3-4). It is commonly produced from vermiculite, perlite, glass fiber, cellulose, or rock wool. Because loose-fill insulation is so easy to install, it is often used to insulate the cavities between joists in unfinished attics.
A major disadvantage of loose-fill insulation is that it eventually tends to settle and lose some of its effectiveness as an insulating material.
Vermiculite and perlite loose-fill insulation are seldom used today as an insulating material in residential construction.