Fiberglass insulation is made from sand and recycled glass cullet that is melted and spun from molten glass into fibers. It has millions of tiny air pockets that help resist the flow of heat and cold. It is installed in batts or rolls. Fiberglass insulation manufacturers recycle more material by weight (up to 40%) than any other type of insulation. Talk about environmental benefits!
A typical pound of fiber glass insulation saves 12 times as much energy in its first year in place as the energy used to produce it, then continues to conserve energy year after year. Like any insulation installed it will save you up to 20-50 percent on your energy bill. It is also fire resistant.