If you’re building or refurbishing a residential property, it’s likely that you’ll receive a densely worded planning condition including the following phrase:
‘Prior to occupation of the development, a scheme of sound insulation shall be submitted for approval.’
But what on earth does this actually mean and what is the purpose of this condition?
The effect of noise on health
The intent of conditions such as this is to ensure that noise levels within residential properties arising due to noise sources outside (roads, aircraft, rail, industry etc.) are controlled to a level where the majority of people can rest and sleep, and at which the adverse health impacts of noise exposure are limited.
Studies have shown that across the EU noise exposure leads to:
- About 910,000 additional cases of hypertension
- 43,000 hospital admissions a year
- At least 10,000 premature deaths per year related to coronary heart disease and strokes
The World Health Organisation has published Environmental Noise Guidelines, which have informed the development of the British Standard BS8233:2014 Guidance on sound insulation and noise reduction for buildings.
BS8233: 2014 guidance on sound insulation and noise reduction for buildings
Within BS8233, limits are set for internal ambient noise levels within bedrooms and living rooms based on the acoustic effects on sleep in bedrooms and the effect on resting, living and communicating in other rooms. Typically, your planning condition will require you to demonstrate that the design of your building controls noise to within these levels.
Often, the Local Authority will also ask you to demonstrate that maximum noise events also do not exceed a certain level – depending on the context of your site this could be noise from passing trains, pedestrians, or even industrial processes.
Gathering the data
Of course, we can’t work out what the noise levels inside a building will be until we know what the noise levels are on the outside, and that’s why the first step is to carry out a site noise survey. All surveys are site specific, but will typically include a series of measurements during both the day and night-time periods so that we can get a good picture of the noise climate across the site.
For a simple development this is enough to let us start on the calculations, but if it’s a more complex site, we can use the survey data to create a computer model of the future buildings and the surrounding noise sources to help us understand how they will be affected by noise.
Crunching the numbers
Once we know the environment we are dealing with, we take a look at the building plans including the size of the rooms and the size of the windows. A little bit of acoustic wizardry (okay, maths – we do some maths) and we can quickly work out:
- Whether BS8233 limits can be met when windows are open for ventilation and, if not:
- What the acoustic specification of the windows needs to be
- What the acoustic specification of any ventilator units should be
This information helps the design team develop the proposals for the building when it moves ahead towards construction, but just as importantly, shows the Local Authority that their condition can be met.
What happens next?
Often, submitting the acoustic assessment at planning stage is sufficient to discharge this condition. The Local Authority may look for evidence that the buildings have been constructed as proposed, so that the results of the assessment stand. In some cases where noise is a concern, you might also be asked for noise readings within the property before it’s occupied.
You might have other noise-related conditions that you also need to discharge, for example if you are using external plant for ventilation a BS4142 assessment is likely to be needed.
Bear in mind as well that residential developments are subject to Approved Document E of the Building Regulations, so you’ll need to consider the acoustic specification of walls and floors within the development. Where there are separating walls or floors between dwellings, it’s a Building Control requirement for these to be tested. You can learn more about this and download our e-book here.
Hopefully we have demystified the ‘scheme of sound insulation’ for you, but if you have any questions or need advice on your project you can always contact us by phone or email and we’ll be happy to help!