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The future of building acoustics in a zero carbon world

Sustainability By Neil Bodsworth, Principal Consultant, Acoustics – 18 January 2023

Meeting room space with people chatting on chairs, acoustic panels on ceiling and glazed window


Head and sholders shot of Neil against brick wall background wearing pink shirt and blue blazer

Neil Bodsworth

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In the world of acoustics, we look at the sound within a building and are often bound by standards and guidelines whether mandatory or advisory. Whilst these guidelines provide a concise steer on the acoustic performance requirements, they may not initially appear to offer the flexibility to allow us to directly reduce the carbon footprint of a building.

The majority of embodied carbon in a building will be associated with the structure, especially when incorporating concrete slabs. Of course, we can review the sound insulation of these slabs and advise if they could be thinner, but, in all likelihood, if the structural engineers have suggested a certain concrete thickness, there will be a reason for this. We would hope that they are already looking to minimise the embodied carbon in their design. Cross laminated timber (CLT) is a great alternative to concrete and steel in terms of embodied carbon, and if it suits the project acoustically, we should certainly encourage it. More often than not, we don’t get engaged until the fundamental concept design has progressed past this pivotal position and it would be too late to make suggestions.

Yes, we advise on internal partitions, but they still need to meet a minimum sound insulation requirement as well as the structural and fire requirements, so we won’t have full reign over their design either. Similarly, once occupied, our design team colleagues in building services will be looking at minimising operational carbon emissions by swapping gas boilers in favour of heat pumps, improving thermal performance, reducing consumption demand and specifying energy efficient services and on-site renewable energy sources. Many of these design factors might be beneficial to the acoustic design, but can we really provide any meaningful contribution to them?

Given all the above, where does that leave us and how can we make a difference? Well, the opportunities are wide-ranging, they might not be as significant as other disciplines could take credit for, but we are doing this for a better future.
Beyond the mandatory requirements for sound insulation that we need to provide for the likes of residential, education or healthcare buildings, many other requirements are advisory or client aspirations. Early engagement with a client to determine if they really do need the high levels of acoustic privacy between meeting rooms, could, for example, mean the sound insulation could be reduced by a few dB here and there. They could still get good acoustic privacy but might not require as much additional material within the overall build-up of a suitable partition. If we are convincing the client they don’t ’need’ the additional performance, we should be following the same process in our designs. Are we adding a ‘safety margin’ to account for potential flanking issues or less than perfect workmanship? Based on a review of a selection of typical drywall options, a 3dB increase in acoustic performance could equate to approximately a 10% increase in the embodied carbon.

Once the acoustic performance has been decided, we can then consider the wall configurations we propose. Of course, acoustic performance is not the only factor in dictating the configuration of a wall but many of us will offer suggested build-ups to ensure the acoustic requirements are incorporated into the early space planning exercises at least. Second to the fundamental plasterboard elements of a drywall system, the embodied carbon of mineral wool type products is likely to be the highest contributor to the overall partition. A better, lower embodied carbon solution may be to suggest an alternative stud arrangement or deeper cavity rather than to fill the cavity with mineral wool.

Absorptive finishes, other than the architects likely wanting to have a say on their appearance, are an aspect of the design that we will often have more control and influence over. There are a vast range of ceiling tiles, wall panels and similar finishes that can and do meet any of the acoustic requirements we might specify. But why don’t we take it a step further, start asking product suppliers for their environmental product declarations (EPDs) as well as their acoustic data and make a concerted effort to specify, recommend or at least consider the acoustic products that provide better carbon credentials.

Traditionally, the better performing absorptive ceiling tiles or wall panels have been mineral wool based. Yes, it’s an excellent acoustic absorber but it’s certainly not the most carbon friendly one. There are now many more material options emerging onto the market that use recycled materials, whether that be recycled plastics or, better still, sheep’s wool – a carbon sequester. If space allows within a room, a greater coverage of a lower acoustic performing material might well have a lower overall carbon impact. However, it’s not just the manufacturing process and materials. A product that needs intensive cleaning on a regular basis or lacks durability might initially look like the better option, but the energy required to maintain the product or the need to fully replace it over the lifetime of the building could easily outweigh the initial up-front savings.

I’m excited to see what will emerge over the next few years in terms of product development. Many suppliers are already on board with the net zero journey and are looking at ways to reduce the carbon impact of their products. The faster the world of acoustic consultants can promote lower carbon options, the sooner manufacturers will need to act and develop new, innovative materials.

So, be ‘that person’ - if an architect or developer asks you to review the acoustic performance of a product, don’t just respond with a yes or no, ask them if they’ve also considered the embodied carbon of that product. Better still, suggest an alternative option if you know of something similar with better carbon credentials – if you can’t do anything directly, encourage others to do so.