Stone Free: The Rockwool Story

Stone Free: The Rockwool Story

James Mills, Product Manager at Rockwool 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.

As those in the insulation manufacturing process know, not all mineral wool insulation is the same. For builders, 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.


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, with the molten lava then cooled and spun 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, as it is known, is then melted in a cupola furnace at a temperature in excess of 1500°C. As the liquid rock pours from the furnace, nature’s process is recreated. Lava flow 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 primary fleece which is compressed and 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.


Not only is stone wool a naturally renewable and sustainable material, it also boasts a unique combination of benefits. It absorbs sound, provides a barrier to fire and retains warmth.


Superior Acoustics

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.

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


Reliable thermal performance

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 can contribute to the reduction of fuel bills year after year.

3 – FIRE

Fire Safe Solutions

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 and also help to protect the building’s load-bearing structure, thereby protecting lives and investment.

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

Flat Roofing

From volcanic rock to high performance building insulation, rock has been re-engineered for a fast, easy and perfect fit. ROCKWOOL Flat Roof Overlay Board has been specifically developed for use on flat roof refurbishment projects.

A comprehensive sound, thermal and fire safe solution, Overlay Board acts as an ideal base layer to install new waterproofing membranes.

It simplifies flat roof repair jobs, lowers material costs, is easily cut and simple to fit. Ideal for both domestic and commercial projects, it is compatible with all commonly used flat roof membranes, including Single-Ply and EPDM, Bitumen membranes, GRP and other cold applied liquid membrane systems.

When you understand the origins of the material and its physical characteristics it’s clear that, for builders, stone wool should be the first choice for building insulation. Rockwool is easy to build to your clients’ requirements for practical, durable and highly effective thermal, acoustic and fire insulation.

For further information on Rockwool click here.

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