The purpose of insulation is to contain heating and cooling efficiency in insulted areas. In some cases in wall construction, it is used as sound barriers as well.Loose-fill insulation includes loose fibers or fiber pellets that are blown into building cavities or attics using special equipment. It generally costs more than batt insulation. However, it usually fills nooks and crannies easier, reduces air leakage better, and provides better sound insulation than natt-type insulation.