CALGreen code 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.
Wall and roof-ceiling assemblies exposed to the noise source making up the building or addition envelope or altered 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:
- Within the 65 CNEL noise contour of an airport.
- L dn or CNEL for military airports shall be determined by the facility Air Installation Compatible Land Use Zone (AICUZ) plan.
- L dn or CNEL for other airports and heliports for which a land use plan that has not been developed shall be determined by the local general plan noise element.
- Within the 65 CNEL or L dn noise contour of a freeway or expressway, railroad, industrial source or fixed-guideway notice 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 65dB Leq-1-hr during any hour of operation shall have building, addition or alteration 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 Section 5.507.4.1 or 5.507.4.1.1, wall and roof-ceiling assemblies exposed to the noise source making up the building or addition envelope or altered envelope shall be constructed to provide an interior noise environment attributable to exterior sources that does not exceed an hourly equivalent noise level (L eq -1Hr) of 50 dBA in occupied areas during any hours of operations
5.507.4.2.1 Site features.
Exterior features such as sound walls or earth berms may be utilized as appropriate to the building, addition or alteration 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.
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.
Design team: Determine if this code section applies; if so, then specify and detail wall and ceiling assemblies and show in the construction documents.
The contractor should install the wall and ceiling assemblies per the construction documents.
Plan intake: The plan reviewer should confirm in the construction documents that STC ratings are included that meet these requirements.
On-site enforcement: The inspector should verify that complying wall and ceiling assemblies are installed correctly per the construction documents.
(Excerpted from ‘Guide to the 2019 California Green Building Standards Code Nonresidential’ – Chapter 5)