How Is Fiberglass Insulation Made?

Fiberglass insulation uses natural, abundant raw materials. Its primary component is sand. Other ingredients include soda ash, limestone, small amounts of recycled glass and binder materials.

Melting

The raw materials are dumped into a furnace, where they are melted at a temperature of about 2600 degrees Fahrenheit (1430 degrees Celsius). The hot molten material is called glass.

Fiberizing

The glass comes out of the furnace through small orifices in the bottom called spinnerettes or bushings. The glass streams, which are nearly 2000 degrees Fahrenheit (1090 degrees Celsius), are blown with jets of hot air or steam until they separate into extremely fine glass fibers.

Coating

A sizing material is applied as the fibers are formed to help bind the fibers together into a stable mat. The binder also contains a wetting agent to allow water to travel freely within the fibers.

Curing

The batts and rolls of insulation pass through a curing oven where the binder dries.

Cutting and Packaging

The resulting blankets of fiberglass insulation are cut into batts or rolls. They are then packaged for shipment.