LEED v4 EQ Acoustic Performance Requirements: HVAC Noise, STC, and Reverberation Time (v4, 2019 addenda)

LEED v4 BD+C EQ Credit Acoustic Performance is worth 1 point for New Construction, Schools, Data Centers, Warehouses and Distribution Centers and Hospitality, and 1-2 points for Healthcare. Schools also have a separate Minimum Acoustic Performance prerequisite. Source: LEED v4 BD+C rating system, July 2019 addenda, pp. 112 and 136-139. This article covers LEED v4 BD+C; LEED v4.1 is not covered. LEED v5 has also been released (USGBC) and is not covered.

LEED v4 EQ acoustic performance at a glance

The EQ Credit Acoustic Performance rewards buildings that limit HVAC background noise, control sound transmission between spaces and manage reverberation time. For New Construction and the other non-school, non-healthcare project types, the credit has four elements: HVAC background noise, sound transmission, reverberation time, and sound reinforcement and masking. School projects follow a different set of requirements built on ANSI/ASA S12.60-2010 Part 1, and healthcare projects follow the 2010 FGI Guidelines. Sound levels may be calculated or measured, so design-stage calculations can support the submission.

Why do these acoustic thresholds exist?

The credit’s stated intent is to provide workspaces and classrooms that promote occupants’ well-being, productivity and communications through effective acoustic design. HVAC noise, sound isolation and reverberation are the three physical factors that govern speech intelligibility and privacy in occupied rooms. The specific limits come from the standards the credit adopts: the ASHRAE Handbook and AHRI 885 for background noise, the composite STC table in the credit, reverberation limits adapted from the Performance Measurement Protocols for Commercial Buildings, and ANSI/ASA S12.60-2010 for schools. For healthcare projects the requirements come from the 2010 FGI Guidelines and the 2010 Sound and Vibration Design Guidelines for Health Care Facilities.

What background noise and reverberation limits apply to classrooms and commercial spaces?

For school classrooms, the credit requires a background noise level of 35 dBA or less from HVAC systems in classrooms and other core learning spaces, following ANSI S12.60-2010 Part 1 Annex A.1, the ASHRAE 2011 HVAC Applications Handbook Chapter 48, or AHRI 885-2008. The Minimum Acoustic Performance prerequisite for schools sets 40 dBA as the HVAC limit, requires acoustic treatment on high-noise sites (peak-hour Leq above 60 dBA during school hours) and sets reverberation requirements: for rooms under 20,000 cubic feet (566 cubic meters), either enough sound-absorptive finish area (NRC 0.70 or higher) to equal the ceiling area, or calculations showing the ANSI S12.60-2010 reverberation time is met; for rooms of 20,000 cubic feet or more, the recommended times in NRC-CNRC Construction Technology Update No. 51.

For New Construction, the credit does not set NC values. HVAC background noise must meet the 2011 ASHRAE Handbook, HVAC Applications, Chapter 48, Table 1 (or AHRI 885-2008, Table 15, or a local equivalent). Reverberation time (T60 at 500, 1000 and 2000 Hz) must meet Table 2: classroom, executive or private office, conference room and teleconference room under 0.6 s; open-plan office under 0.8 s; library under 1.0 s; courtroom with unamplified speech under 0.7 s; gymnasium or natatorium under 2.0 s.

Commercial sound isolation (composite STC minimums, LEED v4 BD+C Table 1):

Multifamily residence, hotel and motel adjacencies have their own rows (50 to 60); the local building code applies if more stringent.

What documentation is required for LEED acoustic submission?

The credit says to calculate or measure sound levels for HVAC background noise, so a measured post-occupancy test is not the only route. Documentation typically covers the HVAC noise calculation or measurement for each space type, the composite STC of adjacent assemblies against Table 1, and reverberation time against Table 2. Where measurements are used, the sound level meter must conform to ANSI S1.4 type 1 or type 2. Large conference rooms and auditoriums seating more than 50 people require an evaluation of whether sound reinforcement is needed; if needed, it must achieve an STI of at least 0.60 (or CIS of at least 0.77), a minimum sound level of 70 dBA and +/-3 dB coverage at 2000 Hz. Masking systems must not exceed 48 dBA. Confirm the documentation list with the current LEED Online credit form.

What mistakes should project teams avoid on LEED v4 acoustic credits?

Four errors to avoid on this credit.

First: applying the prerequisite number to the credit. For schools the prerequisite HVAC limit is 40 dBA and the credit limit is 35 dBA.

Second: missing the classroom volume boundary. The school prerequisite splits at 20,000 cubic feet (566 cubic meters): smaller rooms follow the absorptive-finish or S12.60 calculation route, larger rooms the NRC-CNRC recommended times.

Third: using one STC for all office adjacencies. Table 1 distinguishes standard offices (45) from executive offices and conference rooms (50) and sets 60 for mechanical equipment rooms against occupied areas.

Fourth: submitting commercial values for a healthcare project. Healthcare projects must meet the 2010 FGI Guidelines tables referenced in the credit; Option 1 (speech privacy, sound isolation and background noise) is 1 point and Option 2 (acoustical finishes and site exterior noise) is 1 point.

Frequently asked questions

What is the LEED v4 EQ Acoustic Performance credit worth?

1 point for New Construction, Schools, Data Centers, Warehouses and Distribution Centers and Hospitality; 1-2 points for Healthcare (1 point per option). Schools also must meet the Minimum Acoustic Performance prerequisite.

What HVAC noise level is required for school classrooms under LEED v4?

The credit requires 35 dBA or less from HVAC systems in classrooms and other core learning spaces. The prerequisite requires a maximum of 40 dBA. Both reference ANSI S12.60-2010 Part 1 Annex A.1, the ASHRAE Handbook or AHRI 885-2008.

Does LEED v4 acoustic performance require post-occupancy testing?

Not as a rule. The credit lets the project calculate or measure sound levels, so design-stage calculations can be used. If measurements are taken, use an ANSI S1.4 type 1 or type 2 meter.

What STC rating is required between offices?

Standard office to standard office requires a composite STC of 45; executive office to executive office, conference room to conference room and office or conference room to hallway require 50; mechanical equipment room to occupied area requires 60. For school classrooms, the credit refers to the STC requirements of ANSI S12.60-2010 Part 1 rather than listing values.