4.6 Sound Insulation Details & Service Penetrations

One of the key factors affecting the acoustic performance of separating elements is the acoustic performance of details, flanking elements and services penetrations. It is vital that these elements are addressed carefully.
Flanking and Junctions – Flanking is an important point to consider during the design stages. For high performance buildings, an acoustic consultant should be appointed. Sections 4.7 - 4.10 provide a range of details.

Sealing junctions - As a rule of thumb, all junctions and joints should be sealed with non-hardening mastic. Any holes smaller than 5mm can be sealed with mastic. Large holes should be sealed with plasterboard or mortar as appropriate.

Resilient bars are an important method of boosting the performance
of stud walls. Care must be taken to ensure that the flexibility of the resilient bar is not breached. See sections 4.8 and 4.10.

Services are one of the major reasons for short falls in sound insulation and this is usually due to the poor layout of services during the design stages. It is vital to consider service runs, location of crosstalk attenuators and penetration details. See sections 4.9 and 4.10.

Structures are often overlooked during the design stage. If not considered, details around partitions can become difficult to make good.

Site Construction Details - Having worked across many sites, there are many common faults which have been observed. Most issues relate to services, see sections 4.9 and 4.10.

4.7 Sound Insulation Details - Junctions and Penetrations

4.8 Sound Insulation Details - Resilient Bars and Flanking

4.9 Sound Insulation Details - Services and Structure

2.1 Attenuation Incorporated into a Facade

One of the main difficulties in designing low energy buildings can be the prevention of noise break-in via vented facades. This chapter looks at a range of options and details which can be used to prevent environmental noise break-in from motorways, dual carriageways, trains, aeroplanes, inner city noise and other noise sources.

To overcome this issue an attenuator is selected and incorporated into the facade. This attenuator is typically combined with a damper such to control the flow of air into the building with a weather louvre being used externally to provide the weather protection. MACH Acoustics describes this combination of units as the ‘NAT Vent Box’. The outline schematic of this system is shown below. The damper can take the form of a thermal volume control damper, open-able vents within the facade, thermal insulated doors etc.

2.5 Window Details

The details used to incorporate the attenuation box into a seat or play box are very similar to those used when incorporating the NAT Vent Box into the facades of buildings. As noted, it is often easier to extend out the facade line of single storey buildings such to accommodate deep attenuators. This in turn means that it is seen as possible to provide natural ventilation irrespective of noise levels. The illustration below 1 was used to control noise break-in to a sensitive office space in close proximity to a major motorway.

Installation of the Attenuator
Forming the NAT Vent Attenuator by tessellated, W-shaped foam blocks, means that this product can easily be dropped into a timber enclosure or metal duct work. The W-shaped tiles compress and can be cut to any size; hence these units are extremely easy to accommodate into the facade of a building 2

2.12 Solar Shading and Acoustic Screening to Open Windows

‘Acoustic Scaled Models of Vented Facades’ is a technology which has been developed by MACH Acoustics. This technology enables the effects of acoustic screens attached directly to the facade of a building to be assessed. Scaled models are typically used to assess the acoustics of auditoriums during the design stages. For major concert halls, a scaled model of the auditorium is built such to assess its acoustic performance and characteristics. Scaled models are used due to their practical, accurate and cost effective nature. The same principles apply to the design of screened acoustic facades. MACH Acoustics has developed a method of assessing the acoustic resistance of screens attached directly to the facade of a building by means of scaled models.

The illustration below shows two design options where screened facades were proposed in order to add acoustic attenuation to a vented facade within an inner city office block. This method of noise control is simple, cost effective and provides the additional acoustic resistance such to prevent inner city noise being a nuisance within the office accommodation. Screened facades are also a good method of meeting the requirements set out by BREEAM. The drawback of this system is that these screens can only enhance the performance of an open-able window by around 5 to 7 dB, meaning that these facades can only be used when external noise levels are moderately high.

2.13 Screening under overhangs and above roof

The scheme below provides three design options incorporating acoustic screens into the facade of a development. In these instances, the air inlet vents are acoustically screened by baffles which break the line of sight to a given noise source. The acoustic screens are, in this instance, created by extending parts of the facade or adding panels to the facade such to cover the air inlet vents.

Option 1 - Overlapping Façades
With a perpendicular air inlet to the facade, this design provides an ideal screen to a noise source propagating from the left-hand side of the building.

Option 2 - Solar Shading and Acoustic Screening
Here a solid transparent screen incorporated into the solar shading, provides acoustic screening to a noise source directly in front of the building.

Option 3 - Photovoltaics used as Acoustic Screens
Photovoltaics provide acoustic screens in this instance. The photovoltaics are used to provide solar shading, power and acoustic attenuation, all within the building’s facade. Off-setting the photovoltaics and placing the air vents directly behind these panels provide high levels of acoustic resistance.