Sound insulation and implications regarding Building Regulations
08 September 2015
Author: Chris Dilworth, director of acoustics at AWN Consulting Limited, chartered and European engineer
The Department of the Environment, Community and Local Government (DECLG) published new Building Regulations pertaining to sound in December 2014. An updated and enhanced Technical Guidance Document (TGD) E Sound followed in January 2015. The key aspects of the new guidance may be summarised as follows:
- For the first time in Ireland, minimum standards of sound insulation performance have been used to define ‘reasonable resistance to sound’;
- Reverberation in common internal parts of buildings has been introduced as an issue requiring consideration, and;
- Mandatory pre-completion testing is required in order to demonstrate compliance with the requirements of the regulations.
Sound insulation performance
Table 1 from TGD E, reproduced below, stipulates the minimum levels of performance required in order to demonstrate compliance with the requirements of the regulations.
|Table 1||Sound performance levels(Par. 1.1.1)|
|Separatingconstruction||Airborne sound insulationDnT,w dB||Impact sound insulationL’nT,w dB|
|Floors (including stairs with a separating function)||53 (min)||58 (max)|
Airborne sound insulation refers to the control of noise from sources such as voices, televisions and hi‑fis. The numerical value in the table is a measure of the extent to which noise is attenuated as it passes across the separating construction, hence the higher the value the better the performance. Impact sound insulation refers to the control of noise from footfall, moving furniture etc. The numerical value in the table is a measure of the magnitude of noise transmitted into the room below the separating construction, hence the lower the value the better the performance.
TGD E provides examples of four wall types and three floor types which, if constructed correctly, should achieve the performance level set out in Table 1. This guidance has been considerably expanded compared to that provided in previous versions of TGD E, with two new wall types, additional sketch details and increased attention to the control of flanking noise transfer.
The new guidance in relation to reverberation control is intended to “protect residents from noise produced from reverberation in common internal areas outside the dwellings”. Two methods are provided in order to satisfy the relevant Regulation, details as follows.
- Method A: Apply an acoustically absorptive material of a given standard to an area that is a function of the area of the floor (in entrance halls, corridors or hallways) or the combined area of stair treads, landings and top floor ceiling (in stairwells or stair enclosures);
- Method B: Apply an acoustically absorptive material to an area derived by calculation (only in entrance halls, corridors or hallways). In some instances this approach may result in a requirement for less absorption than Method A, albeit this may necessitate the use of a higher performing material.
In order to demonstrate that this Regulation has been fulfilled, it will be necessary to supply evidence in the form of a description of the space in question, confirmation of the Method employed, details of the acoustic material and coverage area along with plans indicating the assignment of the material.
Sound insulation testing
The single most important element of the revised Regulations is the requirement for mandatory sound insulation testing in order to demonstrate compliance. Testing is required on a proportion of dwellings on every development site, with the actual number of tests being derived through reference to detailed guidance provided in TGD E relating to the number of units and different construction types.
If the dwellings in question have been built using constructions other than those listed in TGD E, they are subject to increased frequency of testing. This can be overcome by following the procedure for “Assessed Sound Details”, which will permit a “non-standard” construction to be tested at the reduced frequency applicable to the example constructions in TGD E.
TGD E encourages early testing of the first dwellings planned for completion, in order to capture any problems at an early stage. In the event of a failed test, it is necessary to undertake remedial work, re-test and (following a favourable result) increase the number of tests conducted in respect of any dwellings not yet completed.
The test procedures to be followed, as set out in TGD E, are defined in the relevant Irish and International Standards. They require specialist knowledge and instrumentation, such as the building acoustics kit shown in Figure 1.
TGD E places a strong emphasis on the competence of testers, as illustrated by the following extracts:
“2.1.2 Competency of Tester
To ensure a proper standard of testing, it is essential that persons are competent in the measurement of sound insulation in buildings to the relevant ISO Standards i.e. ISO 16283 Part 1 and ISO 140 Part 7 series, possess sufficient training, experience and knowledge appropriate to the nature of the work he or she is required to perform having particular regard to the size and complexity of such works.”
“Sound insulation tests carried out by a person certified by an independent third party to carry out this work offers a way of ensuring that such certification can be relied upon.”
Accordingly, DECLG encouraged the acoustics industry in Ireland to explore options that would support the availability of competent testers to meet the requirements of the new regime requirements. This led to the creation of the Sound Insulation Testing Register (Ireland), or SITRI.
This independent “not for profit” certification scheme, administered by the Association of Noise Consultants with training provided by the Institute of Acoustics, will provide the certainty and professionalism demanded by Assigned Certifiers, Architects, Building Control, Builders and Developers. The key elements of SITRI include:
- A comprehensive training programme or a thorough review of experience and qualifications, as appropriate;
- A detailed Registration Audit prior to certification as a competent sound tester; and
- Maintenance of an online database of test results.
More information is available at www.soundtestingireland.com.
The new Building Regulations and Technical Guidance Document E pertaining to Sound represent a major improvement in terms of both performance standards and the guidance that is being provided. It is expected that these measures, along with the requirement for testing conducted by suitably qualified persons, will lead to a commensurate improvement in in-situ performance.http://www.engineersjournal.ie/2015/09/08/sound-insulation-and-implications-regarding-building-regulations/http://www.engineersjournal.ie/wp-content/uploads/2015/09/asound1.jpghttp://www.engineersjournal.ie/wp-content/uploads/2015/09/asound1-300x300.jpgCivilbuilding regulations,Ireland