Sounding Off – Acoustics in Residential Design
At first glance, it seems as though residential development is one of the few area where there is a clear, documented requirement for acoustic design. From planning noise impact, through to design and pre-completion testing in accordance with Approved Document E of the Building Regulations. There’s a standard which needs to be complied with. Why, then, are there still so many noise complaints from residents?
In our opinion, three main things need to be put right in residential acoustic design.
BS 8233:2014 sets standards for internal noise levels in residences (from external noise sources) which allow appropriate conditions for rest and sleep. These standards are compatible with World Health Organisation recommendations and strike a good balance between health and amenity, and practicality. The problem is local authorities are patchy in whether and how they require developers to demonstrate that the standard is met.
From the developer’s point of view, commissioning an acoustic assessment for planning can lead to additional costs if it shows that natural ventilation via open windows isn’t an appropriate solution. It’s therefore vital that the Local Planning Authority take responsibility in ensuring the appropriate design of all new residential developments. Whilst it might increase initial costs to the developer, the relative savings in terms of residents’ health and well being should outweigh this.
Approved Document E (ADE) sets airborne (controlling e.g. voices and music) and impact (e.g. controlling footfall) sound insulation standards between residential units. However, in our opinion, the acoustic standard required by Approved Document E isn’t a high one. We often investigate sites where there are complaints of noise disturbance, where we find that ADE has been met.
We’ve noticed an increasing trend for developers to require that ADE exceeds by at least 5 dB. This seems to provide a greater perception of quality for potential tenants as well as reducing the likelihood of disturbance. The uptake of this enhanced performance criterion suggests that it does not significantly impact developer costs. This makes us wonder whether the next revision of the Building Regulations will see this built in as a requirement.
(Don’t!) Do It Yourself
Finally, something we see often is a developer who believes they can design and build in compliance with ADE without consulting an acoustician. Developers who build multiple units on multiple sites to a standard design can certainly get away with this. However, more bespoke sites or refurbishments are fraught with danger for the unsuspecting. Acoustic separation between units is controlled not only by the specification of the partition, but also by how it connects to the partitions around it, and by any sockets and pipework. Did you know you also need to provide some reverberation control to common areas? How about the acoustic requirement for corridor walls and doors? Is the acoustic performance of your separating floor going to be compromised by those recessed lights?
Getting to completion, then failing the acoustic testing required by Building Control is an expensive mistake. There’s no ‘quick fix’ product. This often means significant demolition of the partitions you so lovingly installed to solve the problem. If in doubt, you should engage an acoustic consultant to help you through the design before going on to pre completion testing.
Do You Need Help?
Whoever you turn to, be sure that they are appropriately qualified. Individual acoustic consultants should be members of the Institute of Acoustics (MIOA). To carry out pre-completion testing, consultancies should have either a UKAS or the Association of Noise Consultants (ANC) accreditation.
If you need help and advice with any aspect of residential acoustic design, from planning through to testing, dBx Acoustics would be happy to help!