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All fiberglass insulation, typically made from silica sand and recycled glass, contains at least 20% recycled products from post-consumer or post-industrial sources. Some manufacturers use as much as 40% recycled glass.

Yet the making of fiberglass insulation consumes large amounts of energy and creates more air pollution than other kinds of insulation because it requires baking the components at extremely high temperatures in fossil fuel-burning furnaces. Still, the North American Insulation Manufacturers Association claims that fiberglass insulation saves 12 times more energy within a year after installation than it uses during the manufacturing process.

The binders in traditional fiberglass insulation contain formaldehyde, which the EPA considers a “probable human carcinogen” but that manufacturers say is used in such nominal amounts it doesn’t present a health concern. In fact, some fiberglass batts have earned Greenguard Environmental Institute certification for low chemical emissions.

Still, some manufacturers are making formaldehyde-free alternatives with acrylic or plant-based binders that reduce concerns about off-gassing during manufacturing and after installation. Builders whose clients have a sensitivity to formaldehyde often specify these alternatives, although they cost slightly more than traditional batts.

Cotton Batts

Although the National Academy of Sciences and the American Lung Association have debunked allegations that inhaling glass fibers from all kinds of fiberglass insulation can cause respiratory cancer, some homeowners report throat and eye irritation from fibers that escape into the air during installation, especially in homes whose ductwork is not properly sealed.

Those concerns are behind the growing popularity of non-fiberglass batts, which can be made almost entirely from recycled cotton, sheep’s wool, or mineral wool.

Cotton insulation is the most popular non-fiberglass type. The product contains no formaldehyde or volatile organic compounds, and manufacturers say the denim fibers will not cause respiratory or skin problems for people who aren’t allergic to cotton. In addition, installers do not need to wear protective clothing when handling the insulation, according to manufacturers.

An added bonus is that most of the cotton comes from shredded denim scraps generated by the making of blue jeans and is 100% recyclable.

Cotton is a flammable material, so the batts are treated with ammonium sulfate or nontoxic borate to make them fire resistant; prevent mold, mildew, bacteria, and fungi; and ward off insects.

Manufacturers claim cotton insulation’s thermal properties are comparable to fiberglass and cellulose. Plus, denim-based insulation’s acoustic ratings are about 30% higher than traditional fiberglass batts, so builders sometimes choose it for home theaters.

But it costs up to 20% more than traditional fiberglass batts, and some installers charge more to place it because they complain it’s hard to cut and dulls their cutting tools.

Spray Foam

A favorite among green builders because it seals as well as insulates, spray foam’s thermal performance outpaces other kinds of insulation. Yet making the polyurethane that is a main component of many foams has a greater impact on the environment than other forms of insulation. Still, foam will save more energy per inch of insulation over its lifespan because its R-value is higher. Nonetheless, its installed price makes it the most expensive choice.

Cellulose insulation is made from at least three-fourths shredded newspapers, cardboard, waste paper, and wood pulp, so it surpasses other forms of insulation for recycled content. Besides paper, some cellulose insulation is made from granulated cork, hemp fibers, straw, and grains, although the most common content is recycled newspapers.

Plus, scraps left over during installation can be reused, and the manufacturing process is less energy-intensive than fiberglass and foam and causes less pollution. Still, its organic base makes the insulation flammable, so manufacturers treat it with flame retardants like borate and ammonium sulfate, used in amounts that are harmful only if swallowed. Cellulose insulation produces a lot of dust during installation, so installers are advised to wear respirators.

Because cellulose can absorb moisture, its R-value decreases over time. And if the insulation is exposed to moisture for long periods, it can rot and grow mold. The Cellulose Insulation Manufacturers Association notes, however, that few cases of significant mold growth on cellulose insulation, which is treated with boric acid, have been reported.

Loose-fill cellulose costs less than fiberglass (batt and loose fill), though its installation may be more expensive. Nevertheless, cellulose insulation typically is produced regionally so there’s no need to transport it great distances. And because cellulose is growing in market share, the energy savings and environmental benefits have the potential to be huge.

Information in this post provided by:Sharon O’Malley is a contributing editor to Building Products magazine and ebuild.com.