Poured loose fill is perhaps the easiest form of insulation to install. Commonly made of cellulose, glass fiber, mineral wool, perlite or vermiculite, it comes in bags that can be poured into areas needing insulation. For unfinished attics, the material can be poured between joists and spread with a rake. Loose fill pours easily into cavities that are difficult to fill with batts or rigid insulation.
Loose fill has the disadvantage that over time, it settles. This is particularly a problem in vertical cavities such as walls. Taking care to install it at the proper density minimizes this problem. As with all insulation types, vapor barriers are often needed.