All About Insulation

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OTHER INSULATION OPTIONS

Fiberglass, cellulose and rigid foam insulation are readily available and are the ones most commonly installed. But some other materials are worth consideration, including cotton, wool, straw and strawclay.

Cotton. Available in loose-fill and batts, cotton insulation has the same R-value per inch as cellulose insulation. Cotton insulation is relatively harmless to the installer and home occupants. It is safe to handle and won't shed fibers like fiberglass or rock wool insulation. Most cotton insulation is treated with a flame retardant, but is manufactured without formaldehyde binders. On a batt-for-batt basis, cotton insulation can be at least twice as expensive as fiberglass, although the price fluctuates depending on who's doing the installation. While cotton insulation is a natural product and safe from a human health standpoint, cotton is one of the most chemically intensive crops grown in the United States.

Two major cotton insulation manufacturers, Inno-Therm and Bonded Logic, use recycled cotton fiber trimmings in their products. UItraTouch cotton insulation is made with 85 percent postindustrial recycled content fiber and 15 percent plastic fiber. The cotton is treated with borate for fire and insect resistance.

Sheep's wool is a superb insulator, having a slightly higher R-value than standard fiberglass. One of wool's greatest benefits is that it insulates when wet, a claim that can't be made about many other forms of insulation. Wool is naturally flame resistant, too. Although wool can be damaged by moths, it contains lanolin, a naturally occurring oil that protects it from these insects. To further safeguard wool insulation, some individuals add cedar shavings.

Wool insulation is common in New Zealand, where sheep outnumber people by a wide margin. In North America, you may be able to purchase wool insulation batts from green building suppliers such as Planetary Solutions in Boulder, Colorado, and Eco Wise in Austin, Texas. New Zealand-based Woolhouse International produces a product called Thermofleece Natural Wool insulation, which is sold in the United States. Thermofleece contains boric acid as a flame retardant.

Straw. Some natural builders install straw bales or loose straw in their ceilings to provide high levels of insulation. Straw bales are inexpensive and readily available. Loose straw is lighter than bales and reduces the need to fortify roof framing. To reduce fire potential, straw can be treated with natural flame retardants such as boric acid or clay slip, a watery solution of clay and dirt.

If you're building a new house, using straw bales as insulation and in-fill for the walls can result in an estimated total R-value of 42 for a wall made of 18-inch-wide bales.

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