Loose insulation in attic fills the space between attic joists and rafters, providing a barrier against heat transfer. This type of insulation is often made of cellulose, fiberglass, or rock wool and is installed by blowing or pouring it into the attic space. Loose insulation is effective at reducing energy costs by preventing heat from escaping through the roof during winter and keeping the attic cooler during summer. It is also effective at absorbing sound and reducing noise transmission.