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Hea 05a Acoustic performance

(non residential only)

Number of credits available Minimum standards
2 No

Aim

To ensure the building's acoustic performance, including sound insulation, meets the appropriate standards for its purpose.

Assessment criteria

This issue is split into two parts:

The following is required to demonstrate compliance for:

Pre-requisite

  1. A suitably qualified acoustician (see Relevant definitions) is appointed by the client at the appropriate stage in the procurement process (but no later than completion of outline design) to provide early design advice on:
    1. External sources of noise impacting the chosen site
    2. Site layout and zoning of the building for good acoustics
    3. Acoustic requirements for users with special hearing and communication needs,
    4. Acoustic treatment of different zones and facades.

Acoustic performance standards

One credit

  1. All unoccupied spaces comply with the indoor ambient noise level as detailed in the more rigorous of criteria 2(a) or 2(b) :
    1. Indoor ambient noise level targets within national Building Regulations or other appropriate good practice standards
    2. Where national Building Regulations or good practice standards do not exist for the building type or do not provide indoor ambient noise targets, the indoor ambient noise levels comply with 'good practice' criteria levels outlined in Table - 15.
  2. A suitably qualified acoustician carries out ambient noise measurements to ensure that the relevant spaces (as built) achieve the required levels. Where the measurements identify that spaces do not meet the standards, remedial works are carried out and the measurements repeated to confirm that the levels are achieved prior to handover and occupation.
  3. The sound insulation between acoustically sensitive rooms and other occupied areas comply with the privacy index, as detailed in the more rigorous of criteria 4(a) or 4(b) :
    1. Sound insulation between acoustically sensitive rooms and other occupied areas comply with targets within national regulations or other appropriate good practice standards
    2. Where relevant national regulations or good practice standards do not exist for the building type or do not provide sound insulation performance targets, the sound insulation between acoustically sensitive rooms and other occupied areas complies with the following privacy index:
      Dw + LAeq,T >75
      Where privacy is viewed to be critical by the client and/or design team (e.g. doctors consulting room, consulting room within a bank) or where the room is adjacent to noisy space such as a music room the area should comply with an enhanced privacy index:
      Dw + LAeq,T > 85
      • Dw is the weighted sound level difference between the two spaces
      • LAeq,T is the measured indoor ambient noise level in the acoustically sensitive room (for the purposes of awarding design stage credits, the design ambient noise level can be used).
      The source and receive room sound pressure levels from which Dw is measured in accordance with (EN) ISO 140-4:1998 and rated in accordance with (EN) ISO 717-1:1996. Measurements must be based on finished but unfurnished rooms, accounting for, and to include the effect of, any carpets and acoustically absorbent ceilings specified.

One credit

  1. Rooms/areas used for speech (including meeting rooms and rooms for public speaking) or rooms used for music performance and rehearsal, achieve reverberation times as detailed in the more rigorous of 5(a) or 5(b) :
    1. Demonstrate that the reverberation time or equivalent absorption area for relevant spaces complies with targets within relevant national regulations or other appropriate good practice standards
    2. Where relevant national regulations or good practice standards do not require the control of reverberation time, achieve reverberation times compliant with Table - 16.
      In addition, if relevant to assessed building, all areas used for teaching, training and educational purposes achieve reverberation times compliant with Table - 17 .

Compliance notes

Ref

Terms

Description

CN1

Shell only

Offices - Where it is not possible to define the type of office space due to the speculative nature of the development, i.e. open plan or cellular, it must be assumed that it will be open with an occupancy rate of 1 person per 10m2. If the space is less than 50m2 it would most likely be cellular. Assessments of buildings that are not fully fitted do not need to assess the criteria associated with sound insulation of acoustically sensitive rooms.

CN2

Building types without areas 'used for speech' Where a building type does not have areas 'used for speech', it does not need to comply with the relevant reverberation criteria. In these instances, the two available credits can be awarded where the building complies with the indoor ambient noise level and, if relevant, sound insulation criteria.

CN3

Acoustically sensitive rooms

Where the term ‘acoustically sensitive rooms’ is referenced in this BREEAM issue, it refers to any room/space the design team or client deems to be acoustically sensitive for the purposes of privacy, which may include the following types of space/rooms (where specified);

  1. Single and multiple occupancy offices.
  2. Meeting/interview/consulting/treatment rooms.
  3. Rooms used for public speaking or seminars.
  4. Any other room/space the design team or client deems to be acoustically sensitive for the purposes of privacy.

CN4

Privacy index To increase the ambient noise level, where privacy is required or the ambient targets include a minimum as well as maximum limit, an artificial sound source or sound masking system may be required. Any artificial sound source or sound masking system should be installed and in operation at the time of the acoustic testing to demonstrate compliance.

CN5

Reverberation times Where the reverberation time required by the relevant standard is not appropriate for the type of space/building assessed, the suitably qualified acoustician must confirm why this is the case. In addition the suitably qualified acoustician must set alternative appropriate reverberation times at the design stage and provide these to demonstrate compliance.

CN6

Unoccupied spaces Where the term ‘unoccupied space’ is referenced in this BREEAM issue it refers to the nature of the space for the purpose of carrying out acoustic calculations or measurements, i.e. such measurements must be carried out when the space is unoccupied and therefore devoid of sources of noise other than those associated with the building, such as mechanical services, sound masking systems and noise break in from the environment.

CN7

Other appropriate good practice standards or regulations, As detailed in the assessment criteria it is possible to use a national/local equivalent to the BREEAM requirements stated, however this must be approved by BRE Global. The Approved standards and weightings list can be used to check for previously approved standards or to propose a new national/local standard.

Schedule of evidence required

Req Design stage
Post-construction stage
All

Professional report/study and calculations from the acoustician.

Letter of appointment or other confirmation demonstrating when the acoustician was appointed.

Relevant section/clauses of the building specification or contract and/or formal letter from the project team regarding commitments.

Professional field report/study and calculations from the acoustician post construction demonstrating compliance with the relevant credit criteria.

Evidence, such as a formal letter from the acoustician or their test report confirming that they meet BREEAM’s definition of a suitably qualified acoustician.

Where remediation works have been carried out, professional field report/study and calculations from the acoustician post completion of the works demonstrating compliance with the credit requirements.

Additional information

Relevant definitions

Dw Weighted level difference
Single number quantity that characterizes airborne sound insulation between rooms but which is not adjusted to reference conditions. Note: Weighted level difference is used to characterize the insulation between rooms in a building as they are; values cannot normally be compared with measurements made under other conditions (see (EN) ISO 717-1).
Multiple occupancy offices
Office space that is not cellular in nature, i.e. it is open-plan, and designed to accommodate more than two desk spaces/workstations.
Occupied spaces
Refer to BREEAM issue Hea 01 Visual comfort and note that for Hea 05a there is a specific, unrelated, definition of 'unoccupied' with reference to acoustic testing and measurement, see Compliance notes for details.
Pre-completion sound testing
Tests should be carried out once the build is essentially complete, but may be carried out prior to or post decoration.
Suitably qualified acoustician (SQA)
An individual achieving all the following items can be considered to be 'suitably qualified' for the purposes of a BREEAM assessment:
    Holds a university/higher education qualification or equivalent qualification in acoustics.
    Has a minimum of three years relevant experience (within the last five years). Such experience must clearly demonstrate a practical understanding of factors affecting acoustics in relation to construction and the built environment, including, acting in an advisory capacity to provide recommendations for suitable acoustic performance levels and mitigation measures.
Where a suitably qualified acoustician is verifying the acoustic measurements/calculations carried out by another acoustician who does not meet the SQA requirements, they must first confirm they comply with the definition of SQA and, as a minimum, have read and reviewed the report and confirm in writing that they have found it to:
    Represent sound industry practice.
    Be appropriate given the building assessed and scope of works proposed.
Single occupancy offices:
Cellular office space designed to accommodate one or two desk spaces/workstations (typically no greater than 10m2).

Checklists and tables

Table - 15: A selection of good practice indoor ambient noise level targets in unoccupied spaces

Function of area

Indoor ambient noise level*

General spaces (staffrooms, restrooms)

40 dB LAeq,T

Single occupancy offices 40 dB LAeq,T
Multiple occupancy offices 40-50 dB LAeq,T
Meeting rooms 35-40 dB LAeq,T
Receptions 40-50 dB LAeq,T
Spaces designed for speech e.g. seminar/lecture rooms 35 dB LAeq,T
Concert hall/theatre/auditoria 30 dB LAeq,T
Informal café/canteen areas 50 dB LAeq,T
Catering kitchens 50 dB LAeq,T
Restaurant areas 40-55 dB LAeq,T
Bars 40-45 dB LAeq,T
Retail areas 50-55 dB LAeq,T
Manual workshops 55 dB LAeq,T
Sound recording studios 30 dB LAeq,T
Laboratories 40 dB LAeq,T
Sports halls/swimming pools 55 dB LAeq,T
Library areas 40-50 dB LAeq,T
* Where ranges of noise levels are specified andprivacy is not deemed by the final occupier to be an issue, it is acceptable to disregard the lower limit of the range and consider the noise level criteria to be lower than or equal to the upper limit of the range1 BS8233:1999 Sound insulation and noise reduction for buildings - Code of practice.

Table - 16: Guide to reverberation time, T, at 500 Hz in unoccupied rooms for speech and music

Room volume

m3

Reverberation time T*

s

Speech

Music
50 0.4 1.0
100 0.5 1.1
200 0.6 1.2
500 0.7 1.3
1000 0.9 1.5
2000 1.0 1.6
*Where the reverberation times stated above or in the referenced documents are not appropriate for the type of space/building assessed, the acoustician must confirm why this is the case. In addition the acoustician must set alternative appropriate reverberation times at the design stage and provide these to demonstrate compliance.

Table - 17: Performance standards for reverberation in teaching and study spaces- mid frequency reverberation time, Tmf, in finished but unoccupied and unfurnished rooms

Type of room

(receiving room)

Tmf (seconds)*

Open-plan

Teaching areas

Resource areas

< 0.8

< 1.0

Lecture rooms

Small (fewer than 50 people)

Large (more than 50 people)

< 0.8

< 1.0

Recording studio 0.6-1.2
Control room for recording < 0.5
Libraries < 1.0
Audio-visual, video conference rooms < 0.8
*Tmf is the arithmetic average of the reverberation times in the 500 Hz, 1 kHz and 2 kHz octave bands2Building Bulletin 93: Acoustic Design in Schools, A Design Guide, 2004, UK Department for Education & Employment

Calculation procedures

Testing, measurement and calculation procedures

Where specific guidance on testing, measurement and calculation is not stated in the criteria table above for the relevant building type, or within the relevant standard/guidance referenced, the following procedures can be usedby the acoustician when measuring or calculating the levels required to demonstrate compliance with this BREEAM issue.

Measurements of sound insulation (airborne and impact) should be made in accordance with the relevant part of (EN) ISO 140 series, or the successor to these standards.

For measurements of reverberation time, the relevant principles of (EN) ISO 354:2003 should be used and the guidance provided in (EN) ISO 140-7:1998 should be followed in respect of the number of source and microphone positions, and decay measurements.

For measurements of ambient noise, when no specific guidance is available, the following procedures should be used:

  1. Noise from both internal sources (e.g. mechanical ventilation systems, plant noise, noise masking systems) and external sources (e.g. traffic noise transmitted via the building façade) should be included, and, where windows are openable as part of the background/permanent ventilation strategy, these should be assumed to be open (at their design opening distance) for the purposes of calculations and open for measurements.
  2. If openable windows are not part of the background/permanent ventilation strategy, then these should be assumed to be closed for the purposes of calculation and closed for measurements.
  3. Noise from occupants and office equipment (e.g. computers) should not be included in the measurements.
  4. Measurements should be made in at least four rooms in which noise levels can be expected to be greatest, either because they are on the noisiest façade or because they are on a naturally ventilated façade.
  5. Where different ventilation strategies are used, measurements should be conducted in rooms utilising each strategy. Otherwise, measurements should be made in rooms on the noisiest façade.
  6. T in LAeq,T is taken as the duration of the normal working day (typically 8 hours between 09.00 and 17.00).
  7. Measurements need not be made over a period of 8 hours if a shorter measurement period can be used. In this case, measurements should be made when external noise levels are representative of normal conditions throughout the day.
  8. Measurement periods less than 30 minutes may give representative values for indoor ambient noise levels and may be utilized where this is the case. However, measurement periods shorter than 5 minutes should not be used.
  9. Measurements should be taken in a minimum of 3 locations in rooms at a height of 1.2 m above the floor level and at least 1 m away from any surface.
  10. The measured level of ambient noise should be used to determine compliance with the privacy index. If at the time of acoustic commissioning it is not possible to measure ambient noise levels in the absence of construction or other extraneous noise sources that will not be present when the building is complete, then for mechanical services the lower level of 35 dB, LAeq or the lowest design limit for the acoustically sensitive space should be used.

The above is intended as guidance for undertaking acoustic testing/measurement to demonstrate compliance with the performance requirements in BREEAM. If the acoustician has felt it necessary to deviate from the above procedures, they should provide a reason for doing so and confirm that the alternative procedures are adequate for demonstrating that the building meets the acoustic performance requirements.

Other information

Noise rating (NR) curves

Noise assessments based on Noise Rating (NR) curves are often used by building services consultants to predict internal noise levels due to mechanical ventilation systems. However, the BREEAM requirement uses the indoor ambient noise level, which includes external noise transmitted via the façade as well as internal noise such as that from mechanical ventilation systems. In the absence of strong low frequency noise, LAeq,T can be estimated from the NR value using the following formula:

LAeq,T NR + 6 dB.

Therefore, if the NR value is known, but not the sound pressure levels in the individual frequency bands, an estimate for the indoor ambient noise level can still be determined from the NR value for the building services noise. The LAeq,T for the external noise transmitted via the façade must then be combined with the LAeq,T for the building services.