VIEWPOINT


WHY GLASS MINERAL WOOL COULD BE YOUR BEST OPTION FOR


ACOUSTIC INSULATION Iain Parker, key account manager, Knauf Insulation


IF A CUSTOMER came to the trade counter asking for acoustic insulation, what product would you recommend? Many merchants may instinctively recommend a low-density rock mineral wool slab, such as Rocksilk RS45 slab. But new test data reveals that glass mineral wool can match, and in some cases outperform, rock mineral wool for acoustic insulation in common applications.


Performance parity Acoustic specialists SRL conducted two tests to investigate how glass mineral wool holds up against rock for sound insulation under the international standard EN ISO 354. This measures how effectively a material absorbs sound waves. SRL compared rock and glass mineral wool slabs at different thicknesses to better understand real-world applications.


The results of these tests, known as the Sound Absorption Coefficient (SAC), can be categorized for easier comparison using EN ISO 11654 to provide a Sound Absorption Class ranging from E, the lowest class, to A, the highest.


In this test, both OmniFit Thermal and Sound slab (glass mineral wool) and Rocksilk RS45 (rock mineral wool) achieved the highest possible sound absorption class of A at a 100mm thickness. This means that both products absorb almost all incident sound and are equally suitable for acoustic insulation.


Less is more


What is even more surprising is that during testing, glass mineral wool performed better than rock mineral wool in thinner thicknesses. SRL’s testing showed


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sound absorption performance and is a suitable choice for insulating build-ups such as internal partition walls. OmniFit Thermal and Sound slab also offers several practical advantages: it holds the best- possible Euroclass A1 reaction to fire classification, it’s easier to handle thanks to ECOSE, Knauf Insulation’s plant-based binder, and is compression packed, allowing for more efficient storage and transport.


OmniFit


Thermal and Sound slab offers best in class sound absorption performance and is a


suitable choice for insulating.


that, at a 50mm thickness, OmniFit Thermal and Sound slab outperformed all our rock products and an alternative low- density rock mineral wool slab too.


The OmniFit Thermal and Sound slab again received the best possible sound absorption class rating of A, while the rock products only received a class B rating.


This means that in a typical


internal partition wall, a glass mineral wool product may be a better choice, which leads us to the importance of all this testing: understanding the suitability of products for different applications.


The right product for the application Looking at these test results, it’s clear that OmniFit Thermal and Sound slab offers best in class


There are still situations where, rock mineral wool is still the right choice. If compressive strength is required, such as in a warm flat roof, then rock mineral wool is typically far more suitable for this application. Although both rock and glass mineral wool are usually non-combustible, high-density rock mineral wool can offer levels of fire resistance that are essential in certain parts of the building fabric.


Sound advice


Ultimately, the test results show that acoustic insulation should not be selected on assumption or habit alone. In many internal wall applications, glass mineral wool can deliver equal or better sound performance than rock mineral wool, while also offering many other advantages.


However, the right solution will always depend on the application. Factors such as compressive strength and fire performance remain critical in certain parts of the building fabric. By understanding where each insulation type performs best, builders’ merchants can give more informed product recommendations, help customers choose the right solution for the application and add greater value at the trade counter. BMJ


www.buildersmerchantsjournal.net July 2026


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