slagwol

Slagwol, also known as slag wool, is a mineral wool insulation material made from blast furnace slag, a byproduct of metal production. It is produced by melting slag at high temperatures and forming the molten material into fibers, which are then bound into boards, batts, or loose-fill products. The material is inorganic, noncombustible, and designed to reduce heat transfer and absorb sound.

Slagwol has low thermal conductivity and good fire resistance. Typical values for batt or loose-fill products at room temperature are around 0.035–0.045 W/m·K, depending on density and composition. Densities vary by form, commonly about 20–60 kg/m3 for loose-fill and 60–120 kg/m3 for batt products. It remains stable over a wide temperature range and can be used around hot surfaces and piping when properly installed. The material also offers moisture resistance when correctly installed, though surface wetting can reduce performance.

Common applications include thermal and acoustic insulation of building envelopes, roofs, walls, HVAC ducts, and pipework, as well as industrial insulation. Slagwol products are available as batts, boards, or loose-fill, and are designed to fit a range of building standards and climates.

Manufacturing uses slag as feedstock and binders to hold fibers in place. The fiber composition is based on silicate minerals, with magnesium- and calcium-rich constituents common to slagwol formulations.

Safety and environment: during production, workers may be exposed to respirable fibers; modern slagwol products are enclosed in facings or boards to limit exposure during use. Installation should follow safety guidelines, and indoor exposure at typical levels is generally considered low risk. Slagwol is often marketed as a way to repurpose industrial slag, contributing to waste reduction when produced from recycled byproducts.

History: mineral wool products have been produced since the early 20th century, with slagwol developed as a variant using blast furnace slag. It competes with rock wool and glass wool as a family of insulation materials.