Production Process-How Mineral Wool is made

Today’s mineral wool insulation products are high-tech versions of their predecessors which have been used in buildings for generations. Glass and stone wool insulation are fibre-based products that deliver outstanding thermal performance. Both are made from plentiful, locally-sourced, renewable natural resources – sand and basalt rock are the basic raw materials of mineral wool. 

The raw materials are measured and sent to a melting furnace. For stone wool this is the rock or recycled material plus energy. Manufacturers are working hard to increase the recycled content of mineral wool whilst maintaining the high quality of their product.

For glass wool the raw materials are sand, limestone and soda ash, as well as recycled off-cuts from the production process. Recycled window, automotive or bottle glass is increasingly used in the manufacture of glass wool and it now accounts for up to 85%. The reuse of off-cuts and recycled materials has helped to steadily reduce the energy input required to produce glass wool.

Furnace

The raw materials are melted in a furnace at very high temperatures, typically between 1,300°C to 1,500°C. The smoke created during this process is filtered and flue gases are cleaned to minimise any environmental impact.

Spinning

The droplets of melt exiting the furnace are spun into fibres. Droplets fall onto rapidly rotating flywheels or the mixture is drawn through tiny holes in rapidly rotating spinners. This process shapes it into fibres.

Binding

Small quantities of binding agents are added to the fibres. The structure and density of the product will be adapted according to its final usage.

Curing

The mineral wool is then hardened in a curing oven at around 200°C.

Cutting

The mineral wool is cut to the required size and shape, for example into rolls, batts, boards or it can be customised for use with other products. Off-cuts and other mineral wool scraps are recycled back into the production process, which further reduces inputs and energy requirements.

Packaging

Due to its impressive elasticity, mineral wool can be compressed during packaging to reduce its volume. This makes it cheaper and easier to handle and results in lower carbon emissions due to transportation.

Gases and waste

Gases emitted during the production process are cleaned in filters and after-burners to minimise the environmental impact. Water use in the process is generally confined to closed circuit systems. This has the twofold advantage of reducing fresh water consumption and avoiding the discharge of dirty or polluted water.

Mineral wool manufacturers positively contribute to ‘industrial symbiosis,’ i.e. the converting of residual waste from one industry into the raw material for another - through the use of waste metallurgical slag, spent blasting sand and cullet (waste glass). This both reduces the energy and raw material required for mineral wool production and reduces the waste created by other industries.

Environmentally responsible production

• Positive carbon footprint: Insulation’s exceptional thermal performance properties make our buildings less dependent on energy - for each tonne of CO2 emitted in manufacturing mineral wool, around 200 tonnes are saved during the products lifetime.
• Energy efficiency
  There has been a steady decrease in energy inputs associated with the production of glass and stone wool. Manufacturing mineral wool requires only half the energy needed to manufacture other types of insulation.
• Waste reduction
  Declining levels of waste are being sent to landfill because streamlined production processes require less raw materials and because of the increasing amounts of recycled materials being used in the manufacture of mineral wool.