024 BP 1016

BP 10 October 2016

DOORS & WINDOWS 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 multichambered pvc-u 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 24 BUILDING PRODUCTS | OCTOBER 2016 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 also be 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. However, they are often most encountered in safety and security applications. Interestingly, gas filling of insulated double glazing units has no effect on sound insulation and, in some types of gases, may be detrimental in the face of low-resonance noise such as that emanating from traffic and trains. 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


BP 10 October 2016
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