Sto Product Manager Karine Galla recently penned a piece in Construction Specifier on mineral wool as an option to enhance the thermal performance of continuous insulation on a building’s exterior. While mineral wool has been around for over a century, the article provides an overview on how the insulation is produced today and outlines its many attributes for exterior facades.
Mineral wool is typically made from a combination of melted volcanic rock and steel slag spun into a mass of fine, intertwined fibers. These fibers conduct heat very well, but when pressed into rolls and sheets they create an excellent insulator. In addition to its thermal performance, mineral wool also appeals to designers and specifiers because of its fire resistance. Since mineral wool insulations are naturally noncombustible, they will not burn or release harmful smoke and hot gases.
Mineral wool is also vapor permeable, with a vapor rating of up to 50. This means water vapor can readily diffuse throughout the material; it will not retain water. Since most mineral wool products are made from more than 50% post-industrial recycled content, and contribute so significantly to energy conservation, they are also considered very “sustainable”.
As a result of these performance virtues, mineral wool is increasingly used in building exteriors. Especially when builders are looking to mitigate fire risk, noise intrusion, and energy waste, as well as ensuring moisture control in an “all-in-one-solution”.
Mineral wool insulation has been widely used in industrial settings such as petroleum refineries and power plants, as well as for lofts, cavity walls, flat roofs and heating systems. It has also been used as an insulation layer behind various claddings such as curtain walls, rainscreen facades and exterior insulation and finish systems (EIFS).
While suggesting that mineral wool products warrant consideration, Galla also outlines some of the product’s challenges and important factors to consider in designing a wall assembly with mineral wool insulation. These include: air and moisture control, detailing solutions at the joints and seams, making wind load calculations, ensuring fastener longevity, and determining impact resistance.