Rock and Slag Wool Composition

Rock wool and slag wool insulation is comprised of basically the same raw materials but in different proportions and is produced in the same way. Manufacturers use a mechanized process to spin a molten composition of rock and slag into high temperature-resistant fibers. Their similar properties also produce fairly similar performance attributes. The major difference is in the specific volumes of the various raw materials used to make each product.

Rock Wool Insulation

Rock wool insulation is composed principally of fibers manufactured from a combination of aluminosilicate rock (usually basalt), blast furnace slag and limestone or dolomite. Slag is a byproduct from steel production that would otherwise wind up in landfills. Binders may or may not be used, depending on the product. Typically, rock wool insulation is comprised of a minimum of 70 - 75 percent natural rock. The remaining volume of raw material is blast furnace slag.

Slag Wool Insulation

Slag wool insulation is composed principally of fibers manufactured by melting the primary component, blast furnace slag, with a combination of some natural rock, with or without binders, depending on the product. Typically, slag wool insulation uses approximately 70 percent blast furnace slag, with the remaining volume of raw materials being natural rock.