CalGreen July 2012- Non Residential: 5.507.4 Acoustical control

5.507.4 Acoustical control

– STC : Sound transmission class

‐ OITC : Outdoor‐indoor sound transmission class

– CNEL : Community noise equivalent level

‐    Distance to airports and freeways are removed

‐ Envelope: STC 50 or OITC 40, Windows: STC 40 as 30) or OITC 30 for:

o  Within 65 CNEL noise contour of an airport

o Within 65 CNEL or Ldb noise contour of a freeway, expressway, railroad, industrial or other sources determined by the General Plan

‐ Buildings exposed to 65 dB where noise contours are not available:

o Envelope: STC 45 or OITC 35,

Windows: STC 40 or OITC 30 ‐ Performance method: provide interior noise environment not exceeding 50 dBA

 

SECTION 5.507 ENVIRONMENTAL COMFORT

 

CALGreen Section: 5.507.4 Acoustical control. Employ building assemblies and components with Sound Transmission Class (STC) values determined in accordance with ASTM E90 and ASTM E413 or Outdoor-Indoor Sound Transmission Class (OITC) determined in accordance with ASTM E1332, using either the prescriptive or performance method in Section 5.507.4.1 or

5.507.4.2.

 

Exception:  Buildings with few or no occupants or where occupants are not likely to be affected by exterior noise, as determined by the enforcement authority, such as factories, stadiums, storage, enclosed parking structures, and utility buildings.

 

5.507.4.1 Exterior noise transmission, prescriptive method. Wall and roof-ceiling assemblies exposed to the noise source making up the building envelope shall meet a composite STC rating of at least 50 or a composite OITC rating of no less than 40, with exterior windows of a minimum STC of 40 or OITC of 30 in the following locations:

 

1. Within the 65 CNEL noise contour of an airport

 

Exceptions:

1. Ldn or CNEL for military airports shall be determined by the facility Air Installation

Compatible Land Use Zone (AICUZ) plan.

2. Ldn or CNEL for other airports and heliports for which a land use plan has not been developed shall be determined by the local general plan noise element.

 

2. Within the 65 CNEL or Ldn noise contour of a freeway or expressway, railroad, industrial source or fixed-guideway noise source as determined by the Noise Element of the General Plan

 

5.507.4.1.1 Noise exposure where noise contours are not readily available. Buildings exposed to a noise level of 65 dB Leq-1-hr during any hour of operation shall have exterior wall and roof-ceiling assemblies exposed to the noise source meeting a composite STC rating of at least 45 (or OITC 35), with exterior windows of a minimum STC of 40 (or OITC

30).

 

5.507.4.2 Performance method. For buildings located as defined in Sections A5.507.4.1 or A5.507.4.1.1, wall and roof-ceiling assemblies exposed to the noise source making up the building envelope shall be constructed to provide an interior noise environment attributable to exterior sources that does not exceed an hourly equivalent noise level (Leq-1Hr) of 50 dBA in occupied areas during any hour of operation.

 

5.507.4.2.1 Site features. Exterior features such as sound walls or earth berms may be utilized as appropriate to the project to mitigate sound migration to the interior.

 

5.507.4.2.2 Documentation of compliance. An acoustical analysis documenting complying interior sound levels shall be prepared by personnel approved by the architect or engineer of record.

 

5.507.4.3 Interior sound transmission. Wall and floor-ceiling assemblies separating tenant spaces and tenant spaces and public places shall have an STC of at least 40.

 

Note:  Examples of assemblies and their various STC ratings may be found at theCalifornia

Office of Noise Control: http://www.toolbase.org/PDF/CaseStudies/stc_icc_ratings.pdf .

 

Intent:

Where buildings are sited in the noisy areas described in this provision, the intent is to keep sound levels low enough to carry out the activities that take place inside the building without the distraction or discomfort of unwanted noise.

 

Change for 2012: This section is proposed for modification in response to comment to include performance and prescriptive measures to achieve compliance with exterior noise transmission, using measurements recognized in acoustical industry practice. It coordinates noise exposure locations with those cited in local general plans and aligns also with Chapter 12 of the California Building Code for noise control in residential occupancies regulated by HCD.

 

Existing Law or Regulation:

There is NO current law or regulation for this code provision for nonresidential buildings. There may be local ordinances that apply in those communities that have noise exposure such as

commercial airports.

 

Compliance Method:

Design Team: The designer should determine if a building’s location requires compliance, then specify and detail wall and ceiling assemblies and show in the construction documents, show on

plans and/or sections the placement of sound walls and floor/ceilings.

 

Contractor: The contractor should install the wall and ceiling assemblies as designed.

 

Suggestion:

Employing the services of an acoustical engineer is another option to assist with compliance and is required if using the performance method.  Choose an assembly from the “examples of assemblies” link that meet the corresponding sound ratings class.

 

Note: Examples of assemblies and their various STC ratings may be found at:

http://www.toolbase.org/PDF/CaseStudies/stc_icc_ratings.pdf .

 

Enforcement:

Plan Intake: The reviewer and/or plan checker should review the plans, specifications and calculations to confirm that STC ratings are included which meet the requirements of this section.

 

On-Site Enforcement: The inspector should review the permit set of plans and product data sheets to verify that complying wall and ceiling assemblies are installed correctly.

 

Intent:

CBSC adopted these sections as modified for new construction to provide clarity to the code user regarding environmental acoustics. When installed as part of an addition or alteration, new

exterior walls and roof-ceiling assemblies in buildings located near specified noise-producing neighbors, as well as new wall and floor-ceiling assemblies separating tenants inside the building,

shall comply. The proposed provisions are intended to have a positive health and psychological

impact on building occupants and promote healthy work attendance and increased productivity.

 

 

Compliance and Enforcement: See § 5.507 of this guide