Loose Fill Insulation Materials

Most house attics are insulated with loose fill or blown-in insulation. This is usually installed during construction, after the roof is framed and sealed, but before the attic is closed off. The material typically is blown-in with hoses and spread between the joists in the roof, usually after some moisture barrier has been laid. The material is not fastened but left loose in the attic spaces.

Cellulose

The most common type of loose fill insulation is cellulose. This is made from recycled paper, primarily old newspapers. It is treated with non-toxic, fire-retardant chemicals and shredded. Cellulose is inexpensive, easy to use and has a high insulating value, an R-value for heat resistance of 3.5 per inch. It does tend to settle over time and sometimes must be replenished or covered with fiberglass batts.

Fiberglass

Another type of loose fill insulation with recycled material is fiberglass. This typically is formed into beads or pellets, which are blown into the attic cavities. Its recycled content varies by manufacturer, but some types contain up to 40 percent recycled material. It is more resistant to moisture than cellulose, but is less fire-retardant; it does not burn but will melt under heat. Its insulation value per inch is about 3.

Rock Wool

Rock wool, once a very common attic insulation, has now largely been replaced by cellulose. It is naturally very fire-retardant and can be used close to chimneys and stove pipes. Made from recycled wool fabric, it is also called "mineral wool" or "slag wool." It is not very airtight and may not be available everywhere. Its insulation value per inch is 2.8.

Cotton and Denim

Cotton is another fabric-based insulation, now sometimes made with recycled denim collected from clothing manufacturers. It is widely available and has an insulation value per inch of 3, slightly less than cellulose. It does not dry quickly and will be permanently damaged if it gets wet, but is fairly fire-retardant.

Minerals

Some loose fill insulation is all-natural material, most commonly the mineral vermiculite. It is naturally fire-resistant and moisture-resistant, and is used mainly to insulate concrete-block construction. It's not available everywhere, and some varieties may contain traces of asbestos. It is seldom used now. Another seldom-used mineral product is perlite, similar to vermiculite. and still used to insulate concrete-block construction.

References

• Cellulose Insulation Manufacturers Association: What Types of Insulation Are Available?
• North American Insulation Manufacturers Association: Types of Home Insulation and Labeling
• Insulation Guide: Insulation Types
• Department of Energy: Insulation Fact Sheet
• Insulation4Less: Roof Insulation
• Energy Savers: Loose Fill Insulation