Rock-solid insulation credentials

With clients demanding versatility as well as robust credentials from insulation, Paul Barrett of Rockwool puts stone wool under the microscope.

The ingredient of stone wool insulation is a hard, dark volcanic rock – basalt – that is formed when lava reaches the planet’s surface. Around the Pacific Rim and Hawaii, in particular, volcanic activity produces violent eruptions of dust ‘pumice’ as well as strands of material, which is formed as lava falls through cold air draughts. These strands are nature’s original stone wool.

As far back as the beginning of the 20th century, scientists began to examine the material to determine its potential insula- tion properties. Miniature artificial volcanoes were then created in factory conditions to produce stone wool in commercial quantities.

The production process is a technological replica of the inside of a volcano, spinning and cooling lava in a controlled environ- ment. The process begins with the base rock being graded and crushed along with other carefully-selected ingredients, such as recycled stone wool, to form the 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.

Finally, 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 thick- nesses, it is then prepared and packaged to form an extensive range of products for a wide variety of applications.

Extra benefits

Not only is stone wool a naturally renewable and sustainable material, it also combines key benefits for construction projects – sound absorption, fire resistance and thermal insulation. Its excellent acoustic properties are due to the material’s dense, non-directional fibre structure, which ‘traps’ sound waves and dampens vibration.

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

Light and mid-density products can dramatically improve acoustic performance by ‘soaking up’ airborne 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.

Heavier structural products can be used in floating floor constructions to absorb impact noise by damping vibrations, while the heaviest products can add mass to a building element, minimising sound transmission.

Fire resistance

Being created using a similar process to that which occurs at the heart of a volcano, stone wool is designed to tolerate temperatures up to 1000°C without burning, thus giving it the ability to stop the spread of flames during a blaze. Furthermore, stone wool products can protect the building’s load-bearing structure, buying crucial time for building occupants to evacuate.

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.

Extra attention to design must be taken to avoid the possibility of flames spreading through cavities or along service pipes or cables. Due to the different combination of plastic and metal elements in each service, fire stopping systems must be designed, manufactured and installed to cope with the individual needs of a project.

Ideally, specifiers should look for stone wool insulation products that have been awarded the highest possible European classification – namely those designated ‘A1 non-combustible’.

Reliable thermal performance

Stone wool insulation is also proven to deliver 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 energy needed to keep buildings warm in winter, stone wool insulation can also maintains a cool interior temperature during the summer. This type of insulation can be used on both new build schemes as well as upgrading existing buildings – by adding an insulated external render system, for example. This approach to refurbishment causes minimal disruption to occupants and will cut fuel bills in the long run.

Stone wool insulation shields the build- ing fabric, improves fire safety, minimises noise and ensures thermal comfort. The material’s physical characteristics, coupled with all the benefits it brings, combine to make a strong case for specifiers who are looking for an all-round material for building insulation.

Paul Barrett is product manager at Rockwool