Blown-in insulation is a very efficient form of insulation that effectively fills hard to reach areas or nonconforming spaces. There are two types of loose-fill material used, cellulose or fiberglass. Cellulose is primarily made of treated recycled paper. Fiberglass is made of glass fiber bonds and a resin. Most blown-in insulation is engineered for professional use. It is installed by using a specialized blowing machine to blown the material into finished walls or onto attic floors.