Winning the war on noise

// the building envelope

Unwanted and intrusive noise is impacting on more and more lives - especially as pressure to build homes on brownfield sites is remorseless. Chris Coxon, Head of Marketing at Eurocell, considers the issue in the context of doors and windows.

While it is unfortunate that walls or floors effective in screening out airborne and environmental sound may be less so in the face of impact noise, and so require different considerations; mass, when it comes to masonry, is key to achieving attenuation success. Obviously, Approved Document E of the Building Regulations 2010 devotes significant attention to testing, and construction detailing of various wall types.

However, and as it implicitly acknowledges, completely sealing the structure is impossible – especially where one needs to punch through it with doors and windows, so creating a vulnerability to sound in the envelope.
And here the Regulations are less helpful, barely considering the issue at all. Approved Document N, dedicated to glazing, is similarly silent, concerning itself only with safety; while AD L – the Building Regulation most cited in the context of doors and windows, troubles itself only with energy – and not sound – efficiency.
For guidance then, we must look elsewhere: such as in BS EN 12758, Glass in Building – Glazing and Airborne Sound Insulation and BS 8233 2014 Sound Insulation and Noise Reduction. The latter is a comprehensive document deeply complex in calculation and detail, and is not to be approached lightly or by the generalist; while BS EN 12758 gives values for the sound insulation of windows.
The first thing to consider in respect of doors and windows is fit and quality – an area where modern PVC-U items may be thought to have considerable advantages. First, not only are multi-chambered PVC frame profiles inherently sound attenuating, that they are also warp-free is important as any kind of distortion in the frame can seriously reduce the effectiveness of the seal.
The reveals of windows should also be well sealed to prevent sound getting into the wall cavity. At a junction with a separating wall, it is desirable to close the external cavity with a flexible closer, such as Rockwool. If the cavity is likely to be filled for purposes of thermal efficiency, then the closer is unnecessary. Some window specifications see the addition of an EDPM strip, fitted to the exterior of the window frame and lapping onto the cladding of the building. Designed to improve weather-tightness, these also provide increased noise attenuation.
It may be also important to consider other aspects of the glazing system. Trickle vents, for instance, are a pathway for noise; acoustic-rated vents are available, although these are a costly addition.
In respect of doors, the mass – as alluded to above in the context of masonry – is important as is, like windows, fit. It is essential that the door forms an airtight seal against its frame when closed, and joints between wall and frame properly stopped. Thresholds are necessary and even escutcheons for keyholes should be considered in the most extreme circumstances.
Surprisingly perhaps, a double-glazed unit (DGU) does not necessarily perform significantly “better than a single pane of mass equivalent to the thicker pane of the sealed unit, and should be used in a frame with good seals to realise its full insulating potential” (BS 8233). As the thickness and mass of a pane of glass increase, so does its sound insulation qualities, yet not exponentially and there are obviously practical limits to this.
Laminated glass performance, when formulated with resins that have enhanced sound attenuating properties, is better than single pane – ‘monolithic’ – glasses yet are often most encountered in safety and security applications.
Again, the width of a cavity in a DGU has little effect except in triple-glazed applications; yet much of that improvement may be attributed to the additional mass of the third glass pane.
Despite this, a cleverly designed DGU – combined with engineered profiled frame materials, and part of a window properly fitted and sealed – can achieve a decent degree of sound insulation, and in excess of that provided by more traditional alternatives. Such a design would necessarily involve a laminated pane, and varying thicknesses of pane. One should be mindful that different pane thicknesses are associated with different resonances of sound; so should be specified in the context of a noise risk assessment – i.e. what type of sound are you most trying to
screen out.
One curious effect is that height has little effect in reducing noise intrusion. This is simply because the higher the building, the more sources of noise it is exposed to and, in high rise or dense urban environments, the reflectivity of hard facades will bounce sound vertically.
Whatever the solution – and it is time the Building Regulations considered sound insulation in the context of DGUs, frame materials and airtightness – with increasing urbanisation, traffic growth, population growth and the use of more mobile and powerful technologies, we will have more noise. Not only more noise, but louder, more intrusive and more upsetting.


www.eurocell.co.uk

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