Acoustic Mineral Wool: The Definitive Guide

Written by Daniel

Mineral wool is a type of insulation that has been used for centuries. It is made from natural materials, such as rock and slag, which are then spun into fibres. These fibres can be used to insulate buildings and other structures. Acoustic mineral wool cavity insulation is a type of mineral wool that is designed to reduce sound transmission. In this article, we will discuss the science of how it works, where it can be best used, and how you can install it!

Introduction to acoustic mineral wool

Acoustic mineral wool (AMV) is an open-cell insulation material that does an excellent job of absorbing both acoustic and thermal energy. Acoustic mineral wool is rigid yet affordable, it is commonly used in construction to fill cavities like stud walls and although it is quite rigid, cutting it is easy. The wool comes in a variety of thicknesses and densities, making it suitable for both household and commercial projects. The material is not only good at acoustic and thermal energy absorption, but it is also very useful for filling cavities. This prevents the cavity from being an open and resonant ‘cave’ like hole which can amplify acoustic energy.

AMW is an excellent acoustic insulation option because it efficiently soundproofs between joists and stud partitions. AMW’s density is also eco-friendly, reliable, extensively used in buildings and throughout the industry, and gives great thermal and fire protection.

The random arrangement of the fibres ensures that no water can penetrate in any direction, making it perfect for soundproofing. It is also rot-proof and non-hygroscopic, meaning that it will not encourage the growth of fungi, moulds or bacteria.

How does it work?

The exceptional thermal, fire and acoustic properties of mineral wool derive from the mat of fibres that prevents the movement of air, and from mineral wool’s inert chemical composition.

It is a very versatile material and can be manufactured to many different densities to give varying properties, formed in various shapes and faced with a variety of sheet materials. The range of products includes loose granular material used for blown insulation of cavity walls, slabs for walls, rolls for loft insulation through to pre-formed and faced pipe sections, ceiling tiles and acoustic panels.

How does it work?

Acoustic Insulation

Porous materials such as mineral wool help to reduce noise by allowing air Movement into the fabric. The frequent changes of air molecules – which cause sound waves- move into the body of the mineral wool, where resistance between particles and the material’s tiny tunnels leads to dissipated energy and heat.

Thermal Insulation

Mineral wool’s thermal performance is due to the entrapment of air in the woolly matrix, which prevents convection. Furthermore, there is little solid material to provide pathways for conduction and radiance, so heat transfer is reduced.

Why use Mineral Wool?

Environmental Sustainability

Compared to other insulations, mineral wool provides energy savings and reduces our dependence on fossil fuels. Not only does using mineral wool as a thermal insulant save many tens of times more CO2 and primary energy than what’s invested in sourcing raw materials, manufacturing, distribution, installation, etc., but these savings starts accruing within just a few years. Furthermore, because the material is recyclable and has recycled content (reducing waste), it helps conserve valuable resources both now AND in the future! Many mineral wool products are rated A+ by the Green Guide, meaning they’re environmentally friendly. To learn more about our sustainability credentials, please visit sustainability credentials.

Fire Protection

Because mineral wool cannot catch fire, it protects buildings from fires and helps to keep them safe.

Acoustic Protection

Mineral wool can absorb sound energy, which means it can help improve the acoustic performance of walls, floors, and roofs. This helps to restrict noise transfer within a building from one room to another or between a building and the external environment.

Thermal Insulation

By trapping heat, mineral wool insulation helps to prevent energy from being lost through building envelopes. Since this conserves power, it also cuts down on harmful greenhouse gases like CO2 and other pollutants that cause global warming and acid rain. In addition to these environmental benefits, thermal insulation provides increased comfort for building occupants (warmer in winter, cooler in summer) and delivers substantial cost savings.

How can you install it?

You can usually find acoustic mineral wool in slabs that are 1200×600, and you can cut it to size with a long, sharp knife. However, be aware that the wool will quickly blunt your blade. To avoid this issue, make sure to sharpen your knife often. When cutting the Wool slab down to size for your project, ensure that it is loose-fitting between the joists. 

To achieve the best sound control, make sure the insulation has a loose fit so that it can easily absorb and reduce noise. If you’re fitting the insulation from below, use Sta-Put consol contact adhesive to hold it in place and glue it to the underside of the floor above.

Follow the steps above for optimal results: screw bars across joists at 400mm centres, then secure two layers of high-density 12.5mm acoustic plasterboard to the bars. If you want an even better outcome, place a layer of Acoustic Membrane between the two plasterboard layers.

If your installation is from above, we recommend removing the floorboards and cutting the insulation slightly narrower than the joists. Then insert the acoustic mineral wool into the cavity space so that it rests on top of the ceiling below, being sure to fill any gaps between each slab. Replace the floorboards using either angular ring nails or screws to prevent creaking when walked on. You can achieve even better noise reduction by installing either our acoustic underlay or at least two layers of other soundproofing mats on top of the floorboards before applying your final floor finish.

Pros and cons of acoustic mineral wool cavity insulation

  • Pros: Budget-friendly, naturally derived material that is resistant to fire and moisture.
  • Cons: Protective breathing gear, such as a mask, must be worn when cutting the material as it causes slivers which can lodge in the skin or be inhaled and irritate the lungs. The material needs to be applied deeply to work properly on its own.


Do I need to wear a mask when cutting acoustic mineral wool?

Yes, you should wear a protective mask when cutting the material as it can cause slivers which can lodge in the skin or be inhaled and irritate the lungs.

How deep does the acoustic mineral wool need to be applied?

The material needs to be applied deeply to work properly on its own. We recommend a minimum depth of 12.5cm.

What are the benefits of acoustic mineral wool?

Some benefits of acoustic mineral wool include fire protection, acoustic protection, and thermal insulation. It is also a budget-friendly option.

What is the difference between mineral wool and Rockwool?

Mineral wool is made from melted minerals, while Rockwool is made from melted rocks. Both materials are effective at acoustic and thermal insulation.

Is mineral wool safe for acoustic panels?

Mineral wool is safe for acoustic panels as long as it is properly encapsulated. We recommend using a minimum of 12.5cm depth to ensure optimal results.

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