Steve Smith, head of product management & business intelligence at Knauf Insulation, summarises what you need to know when it comes to insulation & noise.
Keeping the cold out is usually the primary role for insulation, but there are other ways it can contribute to building performance. As the market starts to pay closer attention to some of these other factors in the pursuit of resilient buildings, it’s essential to ensure you’re taking them into account on your own projects.
Combustible materials are now banned in sensitive applications including on residential buildings over 18m in England & Wales and over 11m in Scotland. Many important voices – such as the Fire Protection Association and Fire Brigades Union – are calling for the ban to be extended to other building types. In these circumstances, choosing non-combustible insulation for all projects not only creates safer buildings, but also reduces the risk of legal action or costly remediation work should regulations tighten further.
While fire safety is the most obvious example, it isn’t the only performance factor on the radar of customers. There’s another issue attracting increasing attention – noise.
Why acoustic performance matters
We know more than ever about the damaging impact of noise pollution. Collectively, it costs Europe £24bn per year in lost productivity, impaired learning and harmed health. And the figures on a personal level are no less stark – with people regularly exposed to busy roads or airports 25 per cent more likely to suffer from depression, for example. As anybody who has ever lived with noisy neighbours can testify, a little bit of noise can do a lot of damage.
Homeowners, businesses, local authorities and developers are becoming more aware of the negative effects of noise, and expect their buildings to do a better job of mitigating it. This means managing the sound that enters a building or room from elsewhere, and also preventing echoes and reverberations within a space.
Approved Document E of the Building Regulations sets out the sound insulation requirements for the external walls and some internal walls within residential buildings in England and Wales, and Section 5 does the same for Scotland. But the regulations are only a minimum standard, and there are other applications in the home where noise-reducing insulation should be considered.
How the right insulation helps
Insulation is one of the simplest and most cost-effective ways to improve the acoustic performance of a building. Based on a typical 3-bed semi-detached home, it can cost as little as £30 extra to soundproof the internal partitions not specified under Approved Document E. For a busy family with noisy children and household appliances, that £30 could transform the way they use their home – creating quieter spaces for work, rest and play.
But this is only the case if the correct insulation is used. Unlike thermal performance, where any R-value can be achieved by any insulation material just by adjusting its thickness, acoustic performance is more complicated. Some insulation materials are fundamentally unsuited to absorbing sound, and will reflect it back into a room, or allow it to pass through undisturbed.
For example, rigid foam insulation boards have a closed cell structure, which absorbs very few sound waves. They are also more prone to unintended air gaps during installation, which can allow sound to ‘leak’ through. In contrary, the fibre structure of Glass and Rock Mineral Wool naturally absorbs much of the kinetic energy of sound waves, turning them into heat. It is also easier to install without gaps.
Which products to use, and when
Choosing an absorbent insulation material is the starting point, but you also need to ensure the product is designed for acoustic performance.
Building acoustics are complex, so there is no single metric for comparing different products in isolation. As a rule of thumb, check that a product is listed as suitable for your proposed application. For example, loft rolls should not be used in walls where noise reduction is required – acoustic roll is the appropriate product in this application. To bring clarity, our Knauf Insulation Solutions Guide includes a simple rating system to help you choose your product based on its acoustic, thermal, fire safety and environmental performance, relative to the rest of our range.
Whether Glass or Rock Mineral Wool is the best solution depends on your application. For internal walls and floors, we recommend using Glass Mineral Wool Acoustic Rolls. For flat roofs, Rock Mineral Wool Slabs are the right solution as their high compressive strength means rooftop traffic won’t compromise their long-term performance. For separating floors, you can use either Glass Mineral Wool Acoustic Rolls or Rock Mineral Wool Slabs.