Stone wool

Stone wool

What is stone wool?

Also known as mineral wool or rock wool, stone wool is created by spinning a molten stream of rock, steel furnace slag and recycled materials. Made principally from volcanic rock, it is comprised of 70% natural raw materials including basalt, dolomite and similar rocks, which are generally melted in a cupola furnace with a carbon-containing energy source using optimal energy and environmental protection recovery systems. 

How do we make stone wool?

1. Composition: The basalt, slag and briquet (recycled stone wool) are stored in silos. These raw materials are then automatically weighed and mixed with coke.
2. Fusion: This mixture is fused through coke combustion in a cupola heated to over 1,500 °C.
3. Fibre drawing / Binder: The fibre is drawn by projecting glass on high-speed rotors. A binder is automatically atomized on the fibres and the fibre core is placed in a pressurized chamber to form a homogenous primary sheet. This blanket is then transported to the batting installation.
4. Batting creeping: 
The arm stacks the stone wool zigzagging perpendicularly on a mat underneath. Batting increases the number of layers to achieve a wider range of basis weights. Using a roller system, the multi-layer wool blanket can be directed and compressed. Crimping straightens the fibres to improve their mechanical characteristics.
5. Polymerisation: 
The binder-impregnated products are transported to an oven heated to over 200°C. The hot air that passes through the stone wool blanket polymerises the resin, which gives the blanket its final thickness and consistency. 
6. Packaging / Palletization: Once out of the oven, the blanket is cut to the required width. Any edge waste is recycled during the manufacturing process. The stone wool blanket can be covered with a paper or aluminium covering, or a glass or asphalt mat.


Stone wool, also referred to as rock wool, is created by spinning molten rock and minerals with steel slag to create a cotton-candy-like wool product.


Infographic : How do we make stone wool ?

What is stone wool insulation?

Effective insulation is essential in any kind of building and technical application to ensure maximum comfort and lower costs. Developed, used and improved by ISOVER for many years, stone wool insulation products combine mechanical resistance with excellent thermal performance, fire safety and high temperature suitability.

All our products come in a range of thicknesses specially tailored for individual applications:

  • Efficient fire protection
    Stone wool provides excellent passive fire protection: it is an incombustible material with the capacity to resist temperatures exceeding 1000 °C without fueling the fire or spreading flames. 

  • Excellent sound absorption
    Non-combustible, stone wool has excellent acoustical dampening properties. It is especially useful when superior fire resistance and acoustical performance are required.

  • High levels of thermal insulation
    The tiny pockets of air trapped within the physical structure of the stone wool reduce airflow and heat flow. It maintains its shape and density over time for long-term thermal performance throughout the lifetime of the building or technical application.

  • Environmentally friendly
    We constantly seek to reduce our resource use and emissions emitted during the production process and supply chain. Stone wool is made of up to 50% recycled content and has a positive energy and CO2 balance after 3 months. 

Why choose stone wool?

Stone wool can be used for insulation and fire protection in many applications. It is particularly suitable for industry given its high temperature resistance and non-combustibility

Some of our most popular products:

  • TECH Loose Wool HT
    Loose stone mineral wool for high-temperature industry applications

  • TECH Slab MT
    Premium performance rigid stone wool slabs

  • TECH Wired Mat MT
    Enhanced thermal and acoustic performance for industrial applications, alongside top-level fire classification

Stone wool insulation or glass wool insulation?

The advantage of stone wool over glass wool is its resistance to high temperatures, making this type of insulation the safest in term of fire prevention.

But did you know that there a stone wool that combines this fire resistance with lightweight?


ULTIMATE™, light stone wool. Experience the difference!

What is the secret behind ULTIMATE™ stone wool?

ULTIMATE™ is the result of more than 25 years of intense research by ISOVER. The new generation of light stone wool completes the wide range of mineral wools, foams and other insulants already available from ISOVER.

Produced using a patented fibersing process, it is an efficient, totally shot-free product made of long fine interwoven fibres. This high-performance light weight mineral wool offers excellent fire protection properties and is up to 50% lighter when compared to traditional stone wool insulation solutions.

ULTIMATE™ combines numerous benefits that are not available in any other single insulation product :

  • Excellent acoustic performance
    ULTIMATE™ insulation has excellent sound absorption properties thanks to the unique internal micro-structure comprising long interwoven fibres. The high air-flow resistivity values from density 36 kg/m3 onwards help to create a quieter environment.

  • Superior thermal insulation
    With no unfiberized material, ULTIMATE™ has exceptional thermal conductivity (lambda) values producing a stronger insulation effect with up to 45% less material than conventional insulation products. ULTIMATE™ can generate energy savings of up to 25% (versus traditional stone wool), as well as reducing your overall carbon footprint.

  • High performance in fire safety and at high temperatures
    ULTIMATE™ insulation guarantees superior fire resistance and excellent thermal stability even at constantly high service temperatures up to 620°C. ULTIMATE™ scores the best ranking in the Euroclass system (classification A1) and has been certified to comply with EN 1366.

  • Significant time, space and weight savings
    Highly flexible, ULTIMATE™ adapts to any geometry. Different installation methods can be used depending on the shape and size of stiffeners to reduce time and costs. What’s more, using rolls instead of slabs significantly reduces space and transport costs (~-40%), and also emissions. Rolls also limit waste due to off-cut leftovers and can easily reduce the amount of mineral wool insulation purchased by 15%.

  • Safe and environmentally friendly
    ULTIMATE™ provides safe, efficient and sustainable insulation. As it is made of natural volcanic minerals, it can be recycled and is biosoluble according EUCEB and RAL and therefore doesn’t pose any health risks.

Discover the full range of ULTIMATE™ stone wool solutions

ULTIMATE™, our light stone wool, has been used for more than 15 years in building, HVAC, industry, marine & offshore and technical OEM applications such as solar thermal, fire doors, acoustic silencers. 


Did you know...?

ULTIMATE™ is available in all product types including rolls, slabs, wired mats and pipe sections.  It can be supplied with additional facings such as reinforced aluminum, glass veil and glass fabric in different colour and gram weights.

How is ULTIMATE™ made?

The patented process for manufacturing ULTIMATETM is similar to that used for glass wool. However, the challenge for our development team was to develop a product capable of operating at much higher temperatures. This was achieved following a breakthrough involving a new patented glass composition and extensive conversion of the basic glass wool manufacturing process.


And you Dave, what do you think about ULTIMATE™?

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