Mineral Wool and Glass Wool Information

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mineral wool glass wool selection guideMineral wool and glass wool are fiber materials made from slag, rock, glass, and minerals that have been melted and spun into filaments. The fibers that comprise mineral wool, rock wool, slag wool, and glass wool are collectively known by a variety of terms, including synthetic vitreous fibers (SVF), man-made mineral fibers (MMMF), and man-made vitreous fibers (MMVF).

 

Despite differences in exact fiber types, the wool types above share common applications based on the characteristics listed below. These qualities are often combined into a single product; for example, mineral wool batt insulation may be installed in a building to provide thermal insulation, acoustic protection, and fire protection.

  

  • Thermal insulation—Mineral wool, slag wool, and glass wool make excellent thermal insulators due to their intertwined fibers that form low-density air cells within the material. Insulation may be produced as loose-fill material for insulating flat surfaces, or batts for ceilings, attics, and ducting.
  • Acoustic soundproofing—Mineral wool and glass wool absorb sonic energy and are often used to improve the acoustic performance of walls, ceilings, floors, and roofs.
  • Fire protection—A major advantage of mineral wool and glass wool products is that their fibers are non-combustible. Their use as thermal or acoustic insulation therefore contributes to the fire safety of the building or area.
  • Sustainability—Mineral wool and glass wool are made of recycled materials such as slag, glass, and other industrial byproducts. It is one of the most energy-efficient building materials: the energy saved from its use as a thermal insulator quickly eclipses the cost of its sourcing and manufacture.

Types

 

A wool's type is determined by the fibers or filament used during manufacturing. The table below compares the characteristics of stone wool (a type of mineral wool) and glass wool.

 

Type

Description

Fiber length

Pressure resistance

Maximum working temperature

Elasticity

Melting temperature

Fire resistance

Tensile strength

Image

Stone wool

Made of volcanic basalt or dolomite, or sometimes slag

Short

High

~750° C

Low

Over 1000° C

Superior

Low

 mineral wool glass wool selection guide

Glass wool

Made of sand, limestone, and soda ash

Long

Lower

~230° C

High

~700° C

High

High

 mineral wool glass wool selection guide

 

Production

 

Production of mineral and glass wool is nearly identical save for the difference in raw materials.

   

  • Raw materials (stone, glass, slag, or sand) are first sent through a furnace and melted at very high temperatures.
  • Melted droplets drop through the furnace and are spun into fibers. Depending on the materials, spinning is accomplished by rotating flywheels or spinners.
  • Binders are then added to the fibers, and a curing oven heats them at moderately high temperatures. The binder reacts to the heat, forming the fibers into wool.
  • Cutters shape the material into rolls, batts, or boards, with cut scraps recycled back into the production process.

   

The video below illustrates a typical mineral wool manufacturing process.

 

Video credit: ROXUL Inc.

 

Standards

 

Mineral wool insulation may conform to production specifications laid out in published standards, including ASTM C726 and BS EN 13162. Additional standards can be found at the Engineering360 Standards Library.

 

Resources

 

Eurima—Mineral/Glass Wool Production Process

 

NAIMA—Overview of Glass, Rock, and Slag Wool Insulation

 

Image credits:

Technical Glass Products, Inc. | Knauf Insulation (both images in table)