INSULATION
MYTH-BUSTING: THE TRUTH ABOUT MINERAL WOOL INSULATION
Almost 50% of insulation installed in 2018 was mineral wool; but there are still some misconceptions. Graham Wroe, Sales Director at Knauf Insulation, makers of both glass and rock mineral wool – talks to BMJ to set the record straight.
Myth: Rock and glass mineral wool have different reactions to fire classifications Truth: Unlike other common insulants, unfaced Glass and Rock Mineral Wool insulation have the best possible Euroclass A1 Reaction to Fire Classification rating so they will not contribute to the development or spread of fire should it occur.
The difference comes when fire resistance is required. Fire resistance measures the ability of a system or construction to resist, and ideally prevent, the passage of fire from one distinct area to another (usually known as compartments). Rock Mineral Wool is often used in constructions where longer periods of fire resistance are required. This is because it has a melting temperature of over 1,000ºC and so can contribute significantly to resist the transfer of heat from the source (the fire) to structural elements within the construction, and through the construction itself. To illustrate how fire performance affects the choice of Mineral Wool material, consider the following application. When converting an attic into a bedroom, the floor between the attic and the room below will need to achieve a certain fire resistance rating to ensure occupants have time to escape should a fire occur.
In most cases, insulation would be added between the joists because a contractor will not be certain of the fire resistance of the existing plasterboard (the insulation would also aid in reducing noise transfer between the rooms). In this circumstance, Rock Mineral Wool would be the optimal solution.
Myth: Rock mineral wool is always better than glass mineral wool for noise reduction Truth: Some people believe that when acoustic insulation is needed, Rock Mineral Wool is best. But our latest research shows that Glass Mineral Wool performs as well as Rock Mineral Wool in certain applications and even outperforms it in others.
Tests were conducted using a standard internal wall build-up comprising a metal stud partition at 600mm centres. Installing a Glass Mineral Wool product designed for use in acoustic applications resulted in a 44.8 dB DnTw reduction in sound. Swapping to a higher density Rock Mineral Wool insulation saw a sound reduction by 43.9 dB DnTw and again by 41.0 dB DnTw with an even higher density Rock Mineral Wool insulation.
Myth: For thermal performance, rigid foam board insulation is better than mineral wool Truth: When looking at the thermal conductivity of a material, this is often true on paper; but this
September 2020
www.buildersmerchantsjournal.net
performance may not always translate into the real world due to the difficulty in achieving the quality of installation required. If the insulation boards are not installed correctly, this creates air gaps between the boards or breaks in contact between the insulation and build-up surface, which can drastically reduce the thermal performance. In contrast, Mineral Wool can be used to fill the entire cavity, and its fibrous structure and compressibility allow it to adapt to the substrate, knitting tightly together to ensure gaps are filled and therefore no thermal bridging occurs. The difference in theoretical declared performance between materials is often milliwatts, while poor installation can give away watts.
Myth: Mineral wool will lose thermal performance if it gets wet Truth: Tests by the European Insulation Manufacturers Association (Eurima) found correctly installed Mineral Wool insulation retained its thermal performance even after 55 years of service.
This demonstrates that if Mineral Wool gets wet during construction, thermal performance recovers when it dries out. This is because Mineral Wool designed for use in external applications such as cavity walls or in rainscreen systems contains water repellent additives. These additives protect the Mineral Wool during installation and throughout its lifespan. However, it highlights the need to use the right product for the application.
Myth: Mineral wool is unpleasant to use Truth: Traditionally, binders used to ‘glue’ the individual strands of Mineral Wool together are oil-based, contain formaldehyde and emit volatile organic compounds (VOCs). But that’s not the only option. For example, we developed ECOSE® Technology, our unique bio-based binder that contains no added phenol or formaldehyde. Our insulation is soft to touch, easy to handle, is low VOC and generates very low levels of dust.
Myth: Mineral wool is not made from sustainable materials Truth: With sustainability climbing up the construction agenda, it is important to address this myth. Glass Mineral Wool is manufactured using recycled glass, reducing the need for virgin materials. In our UK manufacturing plants, up to 80% of the material comes from recycled glass, which would otherwise go to landfill. BMJ
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