What type of material is typically used to provide thermal insulation in firestop systems?

Mineral wool is typically used in firestop systems for thermal insulation due to its excellent fire resistance properties and ability to withstand high temperatures. It is made from natural or synthetic mineral fibers, which are non-combustible and have a high melting point, making them effective at slowing the spread of heat and flames in case of a fire. This material is also advantageous because it provides sound insulation and is resistant to moisture, which further enhances its application in firestop systems.

In contrast, while fiberglass can offer some insulation properties, it does not provide the same level of fire resistance as mineral wool. Steel, although strong and durable, does not serve as insulation but rather as a structural element. Plastic materials, on the other hand, tend to be combustible and are not suitable for firestop applications where thermal insulation and fire resistance are critical. Thus, mineral wool is the most appropriate choice for thermal insulation in firestop systems.