Mineral Wool Residential and Commercial Insulation

Mineral wool forms naturally when strong winds blow through molten lava to create the thin, gold-colored strands that volcanologists call Pele’s hair. Today’s mineral wool insulation is made in a less dramatic process using basalt and iron-ore slag that is melted, spun into fibers, and held together with a phenolic resin. Adjusting the density of the fibers and the resin mix produces different residential and commercial insulation products, including batts, blankets, and rigid and semi-rigid boards. All of these products provide excellent sound attenuation and flame resistance along with R-values of about 4 per inch.

Though the life-cycle impacts of mineral wool­ production—primarily energy consumption—are significant, some of these are mitigated through the use of pre-consumer recycled slag from iron manufacturing. Thermafiber, for instance, uses a minimum 70% recycled slag and offers products at 75% and 90% recycled content, including a darker colored board for curtain walls at 84%. According to Austin Hess, business development manager for Thermafiber, “the U.S. Government’s [EPA] Comprehensive Procurement Guidelines require 75% recycled content for mineral wool, and we are one of the only companies that can produce that product.“