Insulation represents an inherently green building material because it is designed to save energy. Still, while any insulation is better than none, the many choices present a broad range of benefits, with certain products inherently more ecological than others.

Here is a sampling of the major types of insulation, their properties, and their sustainability beyond simply saving energy.


Ubiquitous and economical, fiberglass represents the largest share of the market, comprising more than 50% of the insulation installed in the U.S. in 2007, according to the North American Insulation Manufacturers Association (NAIMA). It’s available in loose form for blown-in installation and in blankets, rolls, and batts for compression installation. Depending on density, both blown and stuffed fiberglass products provide R-13 to R-15 in a 2x4 wall cavity. Medium-density fiberglass designed for 2x6 constructions now provides R-21. In a 9?1/2-inch (2x10) cavity, high-density fiberglass can deliver a whopping R-38.

All fiberglass insulation manufacturers use 25% to 40% recycled glass in their products, according to Paul Bertram, director of environment and sustainability for NAIMA. The balance is sand, an abundant natural resource, with chemical binders added to create loft and a cohesive mat in the case of batt-style insulation.

One ecological issue with fiberglass is that glass and sand have to bake at extremely high temperatures to produce fibers. On the flip side, a typical pound of fiberglass insulation “saves 12 times as much energy in its first year in place as the energy used to produce it,” says Bertram.

Most of the health concerns and allegations made about fiberglass insulation have been retracted or disproved. The National Academy of Sciences (NAS) reported in 2000 that epidemiological studies of glass-fiber manufacturing workers indicate “glass fibers do not appear to increase the risk of respiratory system cancer.” NAS now supports the exposure limit of 1.0 f/cc that has been the industry recommendation since the early 1990s. And as of 2001, the International Agency for Research on Cancer (IARC), on which the California standards for Proposition 65 are based, no longer classifies fiberglass as a human carcinogen.