Stone wool power

As those in the insulation manufacturing process know, not all insulation is the same. For specifiers, however, it’s sometimes difficult to understand where the distinctions lie, what benefits there might be and how the insulation choices they make can impact upon a project or application. Paul Barrett, Product Manager at ROCKWOOL® Ltd looks at where stone wool insulation began and how it evolves into thermal, sound and fire safe insulation that’s capable of impressive, long-lasting performance in a wide variety of applications.

RockWorld imagery, The big picture, lava, vulcanic, stone


It sounds improbable, but the raw ingredient for stone wool insulation is a 200 million year old rock. Basalt is actually a base rock from when the Northern Hemisphere was first laid down.

Around the Pacific Rim and Hawaii, in particular, volcanic activity produces violent eruptions of dust pumice and strands of a material which the locals refer to as Queen Peles hair. It is formed as the molten lava falls through a cold air draft. These strands are nature’s version of what we now recognise today as stone wool.

It was around 1900 that scientists started to look more closely at the material as a potential insulant for a range of applications. The clever part was in creating their own mini volcano in factory conditions, to produce the wool in commercially viable quantities.



The production process for stone wool is a technological replica of the inside of a volcano that spins and cools lava in a controlled environment.

The process begins with the base rock being graded and crushed along with other carefully selected ingredients, such as, recycled stone wool to form a raw material. This charge is then melted in a cupola furnace at a temperature in excess of 1500°C. The liquid rock pours from the furnace and is directed into a chamber where it is spun and transformed into rock strands and stone wool.

The spun strands are then mixed with a binder. Trillions of these strands are collected to form a matt which is then cured. Cut to various lengths and thicknesses it is then prepared and packaged to form an extensive range of products for a wide variety of applications.



Stone wool insulation boasts a unique combination of benefits. It absorbs sound, provides a barrier to fire and retains warmth.


1 - Sound

Superior Acoustics – reducing sound transfer

Stone wool insulation is renowned for its excellent acoustic properties. With its dense, non-directional fibre structure, it effectively traps sound waves and dampens vibration to provide an enhanced noise reducing solution.

The product can be used in three different ways to help reduce sound transfer.


1) Light and mid-density products work to provide airborne sound absorption - these can dramatically improve acoustic performance by 'soaking up' sound. Sound energy causes mechanical movement of the fibres, and fluid friction as trapped air molecules move back and forth inside the small pores - these processes harmlessly dissipate sound energy as tiny amounts of heat.

2) Heavier structural products can act as a resilient layer in floating floor constructions to absorb noise from footsteps and other impacts, by damping vibrations before they're transmitted through the rest of the structure - which would otherwise be re-radiated as noise into the space below.

3) The heaviest products can be used to add mass to a building element, improving sound insulation. The heavier a building element, the more difficult it is for sound to pass through it.


Fully tested to meet the rigorous demands of today’s legislation, stone wool insulation is proven to reduce ambient, impact and reverberation noise.


2 - Fire

Fire Safe Solutions – creating safer buildings

Created using the same process that occurs at the heart of a volcano, stone wool tolerates temperatures of up to 1000°C and does not burn.

In the event of a fire, stone wool products are designed to remain stable and slow the spread of flames. The products are fire-safe and help to protect the building’s load-bearing structure, buying valuable time for occupants to safely escape which helps in protecting lives and investment.

Stone wool fire protection products can be used as an effective barrier in a range of building applications, such as a fire shield for structural steel members, in between rooms and roof spaces, cavity barriers for concealed spaces, and a fireproof cover for pipes and ducts.

Fire stopping products help specifiers conform to current fire regulations. Careful design will also ensure that fire cannot spread through cavities or along the service pipe or cable. With each service run including a different combination of plastic and metallic pipes, ducts, and power and data cables, every element will react very differently to fire. So fire stopping systems must be designed, manufactured and installed to cope with the individual needs of the project.

We’d suggest that specifiers look for stone wool insulation products that have been awarded the highest possible European classification: A1 non-combustible.


3 - Thermal

Reliable thermal performance - reducing energy bills

Stone wool insulation also delivers on thermal performance. Its excellent insulating properties derive from tiny pockets of air trapped within the physical structure of the stone wool.

As well as reducing the heat needed to keep buildings warm in winter, stone wool insulation also maintains a cool interior temperature in summer. It’s energy efficient as well as being environmentally friendly all year round.

Stone wool insulation is not just for new builds. An effective way to improve the thermal performance of existing buildings is to add insulated external render systems. This causes minimal disruption to occupants and will cut fuel bills year after year.

Stone wool insulation shields buildings and their occupants, improving safety, comfort and building value.

When you understand the origins of the material and its physical characteristics it’s clear that, for specifiers, stone wool should be the first choice for building insulation.