Mineral Wool Residential and Commercial Insulation

Thermafiber’s RainBarrier cavity wall insulation, which provides fire protection, controls noise, and sheds moisture, is used primarily in rainscreen applications.

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.“


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