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Last edited 26 Mar 2018
Noise - doors and windows
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.
The issue of noise and how to deal with it in new housing developments is becoming a more complex one. Planning policy and the demand for city centre locations means that brownfield sites which were once considered unattractive are now under development.
How loud is too loud?
The World Health Organisation (WHO) guidelines for community noise recommend less than 30 A-weighted decibels (dB(A)) in bedrooms during the night for a sleep of good quality and less than 35 dB(A) in classrooms to allow good teaching and learning conditions.
The WHO guidelines for night noise recommend less than 40 dB(A) of annual average (Lnight) outside of bedrooms to prevent adverse health effects from night noise. (Lnight is the equivalent continuous noise level over the night-time period (23:00 to 07:00).)
Masonry mass is really important in defeating sound. However, as Approved Document E of the Building Regulations 2010 — which devotes significant attention to the detailing of various wall types — acknowledges: completely sealing structures against noise 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 Regulation is not helpful, barely considering the issue at all.
Approved Document N, dedicated to glazing, is similarly silent, concerning itself only with safety; while Approved Document 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 advantages. Not only are multi-chambered PVC frame profiles inherently sound attenuating, they are also warp-free. This is important as any kind of distortion in the frame can seriously reduce the effectiveness of the seal.
Window reveals 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 are properly stopped. Thresholds are necessary and even escutcheons for keyholes should be considered in the most extreme circumstances.
Surprisingly perhaps, double-glazing 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.
Interestingly, gas filling of insulated double glazing units has no effect on sound insulation and, with some types of gases, may be detrimental in the face of low-resonance noise such as that emanating from traffic and trains.
Despite this, a cleverly designed unit - 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 sealed units, frame materials and airtightness; with increasing urbanisation, we will have more noise. Not only more noise, but louder, more intrusive and more upsetting. It will continue to grow in scale and severity because of traffic growth, population growth and the use of more mobile and powerful technologies: phones and other audio, for instance.
This article was originally published in AT Autumn 2017.
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