WELL v2 Feature 74 is the acoustic chapter of the WELL Building Standard. It covers seven distinct areas of acoustic performance, each with its own threshold, measurement method, and documentation requirement. Projects that approach Feature 74 as a single "acoustics" checkbox routinely fail — not because the acoustic design is poor, but because the compliance process was not tracked systematically from early design through post-occupancy measurement.
This checklist gives you a part-by-part breakdown of what Feature 74 requires, what evidence IWBI's reviewers expect to see, and where projects most commonly fall short. Work through it at three project stages: design, construction completion, and post-occupancy.
To model your meeting rooms and open areas against L07 thresholds, use the WELL v2 Feature 74 Calculator.
What Feature 74 Requires
WELL v2 Feature 74 has seven parts, labelled L01 through L07. The parts address different aspects of acoustic performance:
- L01 — Sound Mapping: Document the acoustic environment
- L02 — Massing and Orientation: Site-level noise management
- L03 — Exterior Noise Intrusion: Interior noise from outside
- L04 — Mechanical Equipment Noise**: HVAC and building services
- L05 — Plumbing Noise**: Pipe and drainage noise
- L06 — Sound Barriers**: Sound insulation between spaces
- L07 — Reverberation Time**: RT60 in occupied spaces
The Compliance Checklist
Use this checklist at three stages: Design (D), Construction Completion (CC), and Post-Occupancy (PO). Mark each item as Complete, In Progress, or Not Applicable.
L01 — Sound Mapping
Requirement: Provide a sound map of the project site documenting noise levels from all significant sources.
Threshold: No numerical threshold — this is a documentation and planning part.
What IWBI needs:
- [ ] (D) Site noise survey identifying sources: traffic, rail, flight paths, mechanical plant, neighbouring uses
- [ ] (D) Noise level measurements or predictions at the building facade, expressed as LAeq and L10 (hourly, daytime and night-time periods)
- [ ] (D) Sound map drawing or GIS overlay showing noise contours at facade level
- [ ] (D) Narrative explaining how the sound map informed building massing, window placement, and room layout decisions
- [ ] (CC) Confirmation that the design decisions from L01 were implemented in construction
L02 — Massing and Orientation
Requirement: Optimise building massing and orientation to reduce noise intrusion from the loudest facades.
Threshold: For projects with exterior noise above 65 dB LAeq (daytime), the design must demonstrate that noise-sensitive spaces (bedrooms, classrooms, meeting rooms) are located on the quieter facades or protected by acoustic screening.
What IWBI needs:
- [ ] (D) Floor plan annotated to show noise-sensitive spaces and their relationship to noise sources
- [ ] (D) Facade noise levels at each elevation (from L01 measurement/modelling)
- [ ] (D) Narrative or drawing showing how sensitive spaces avoid the high-noise facades, or how buffer spaces (corridors, service areas, toilets) are used as noise shields
- [ ] (D) For new construction: confirmation that planning noise conditions are met and that facade glazing specifications reflect the required Rw ratings
- [ ] (CC) Architect's confirmation that layout changes from L02 analysis were retained in final design
L03 — Exterior Noise Intrusion
Requirement: Limit the background noise level inside the building caused by external noise sources.
Threshold:
| Space Type | Maximum Background Noise (LAeq) |
|---|---|
| Sleeping areas (residential, healthcare) | 35 dB LAeq night-time |
| Meeting rooms, private offices | 40 dB LAeq daytime |
| Open-plan offices | 45 dB LAeq daytime |
| Lobbies, corridors, circulation | 50 dB LAeq daytime |
What IWBI needs:
- [ ] (D) Facade element Rw ratings (windows, walls, ventilation attenuators) demonstrating sufficient sound insulation to meet interior levels given facade noise
- [ ] (CC) Acoustic report confirming installed facade elements match specification
- [ ] (PO) Background noise measurements in representative spaces, taken when HVAC is running but occupants are absent. Measurement method: IEC 61672 Class 1 sound level meter, LAeq over minimum 15-minute period, windows and doors closed
L04 — Mechanical Equipment Noise
Requirement: Limit background noise from HVAC, lifts, and other mechanical plant.
Threshold:
| Space Type | Maximum Background Noise |
|---|---|
| Sleeping areas | NR 25 (approx. 33 dB LAeq) |
| Meeting rooms, private offices | NR 35 (approx. 43 dB LAeq) |
| Open-plan offices | NR 40 (approx. 48 dB LAeq) |
| Corridors, lobbies | NR 45 (approx. 53 dB LAeq) |
What IWBI needs:
- [ ] (D) HVAC acoustic design calculations demonstrating compliance with NR targets. Calculations must include: fan power data, duct attenuation, terminal diffuser noise, breakout noise through ceiling tiles
- [ ] (D) Plant room isolation design (structural isolation, acoustic enclosures for high-noise plant)
- [ ] (CC) Commissioning sign-off confirming HVAC systems operate within noise specifications
- [ ] (PO) Background noise measurements taken with HVAC running in normal operation. Separate measurement with HVAC isolated to identify HVAC contribution versus external noise
L05 — Plumbing Noise
Requirement: Limit noise from water supply pipes and drainage systems.
Threshold: Maximum 30 dB LAeq in sleeping areas measured during peak flow periods. For offices, no specific threshold — but noise from plumbing above NR 35 in meeting rooms is a compliance risk.
What IWBI needs:
- [ ] (D) Plumbing layout showing pipe routing relative to noise-sensitive spaces. Drainage stacks should not run through or immediately adjacent to meeting rooms or bedrooms.
- [ ] (D) Specification of pipe insulation lagging (minimum 25 mm mineral wool wrap for soil and waste stacks where adjacent to sensitive spaces)
- [ ] (D) Isolation details for pipe brackets and supports (anti-vibration mounts)
- [ ] (CC) Inspection confirmation that lagging is installed as specified
- [ ] (PO) For residential and healthcare: noise measurements during toilet flushing and peak hot water draw-off periods
L06 — Sound Barriers
Requirement: Provide sufficient sound insulation between spaces to maintain privacy and prevent disturbance.
Threshold:
| Partition Type | Minimum Rw (lab rating) | Minimum DnT,w (field rating) |
|---|---|---|
| Meeting room to open office | Rw 45 dB | DnT,w 40 dB |
| Private office to office | Rw 40 dB | DnT,w 35 dB |
| Meeting room to meeting room | Rw 50 dB | DnT,w 45 dB |
| Healthcare consulting room | Rw 50 dB | DnT,w 45 dB |
| Residential party wall | Rw 55 dB | DnT,w 50 dB |
Note: Lab ratings (Rw) are always higher than field ratings (DnT,w) because on-site construction is never as controlled as laboratory conditions. Typically allow 5–10 dB difference.
What IWBI needs:
- [ ] (D) Partition schedule with Rw ratings for all significant partitions
- [ ] (D) Acoustic detail drawings showing: partition head and base seals, penetrations (electrical sockets, junction boxes, pipe sleeves), flanking paths via ceiling void
- [ ] (CC) Acoustic inspection confirming seals, penetrations, and above-ceiling paths are completed per drawings
- [ ] (PO) Field sound insulation measurements (DnT,w per ISO 16283-1) in representative room pairs. IWBI requires a minimum of three measurement positions per room.
L07 — Reverberation Time
Requirement: Limit reverberation time in all regularly occupied spaces to support speech intelligibility and acoustic comfort.
Threshold:
| Space Type | Maximum RT60 (mid-frequency average) |
|---|---|
| Meeting rooms (all sizes) | 0.5 s |
| Open-plan offices | 0.6 s |
| Classrooms, training rooms | 0.6 s |
| Reception areas, lobbies | 0.8 s |
| Healthcare waiting areas | 0.7 s |
| Fitness studios | 1.0 s |
Mid-frequency average = average of 500 Hz and 1000 Hz octave band T20 or T30 values, measured per ISO 3382-2.
What IWBI needs:
- [ ] (D) RT60 calculations (Sabine or Eyring) for all space types showing predicted compliance. Show room volume, surface areas, absorption coefficients, and calculated T60 at 500 Hz and 1000 Hz minimum.
- [ ] (D) Acoustic treatment schedule: panel type, product name, NRC rating, area, location
- [ ] (CC) Confirmation that specified products are installed in specified quantities
- [ ] (PO) RT60 measurements per ISO 3382-2. Minimum measurement positions: 3 source, 6 receiver combinations per room for rooms > 200 m³; 2 source, 4 receiver for smaller rooms. Report T20 or T30 at octave bands 125 Hz–4000 Hz. Submit arithmetic average of all valid measurements.
Common failure: Measurements taken in empty rooms. WELL requires measurements in "typical occupancy conditions" which means furnished but unoccupied (chairs, desks, and soft furnishings in place, people absent). An empty room can be 20–30% more reverberant than a furnished one.
Documentation Package for WELL Review
Compile the following documents for WELL AP submission:
- Acoustic design report — Pre-construction predictions for L03, L04, L06, L07 with methodology, inputs, and calculated results against WELL thresholds
- Sound map drawing — Site noise survey, facade noise levels, sensitive space locations (L01, L02)
- Specification extracts — Partition Rw ratings, HVAC noise specifications, plumbing lagging specifications (L04, L05, L06)
- Post-occupancy measurement reports — RT60 (L07), background noise (L03, L04), sound insulation (L06), with measurement positions marked on floor plan
- Commissioning records — HVAC commissioning sign-off confirming NR compliance (L04)
- Photographic evidence — Acoustic panel installation, ceiling void sealing, plumbing lagging (L05, L06)
Timeline for Feature 74 Compliance
| Project Stage | Feature 74 Actions |
|---|---|
| RIBA Stage 1 / Schematic | Appoint acoustic consultant. Begin L01 site noise survey. |
| RIBA Stage 2 / Design Development | Complete L01 sound map. Confirm L02 massing. Specify facade Rw for L03. |
| RIBA Stage 3 / Technical Design | Finalise partition schedule (L06). RT60 predictions (L07). HVAC acoustic design (L04). |
| RIBA Stage 4 / Construction | Coordinate with contractor: ceiling void sealing, plumbing lagging, partition head seals. |
| Practical Completion | Inspect acoustic details. Confirm HVAC commissioning. |
| Post-Occupancy (3–6 months) | Measure RT60, background noise, sound insulation. Compile documentation package. |
Standards Referenced
WELL v2 Feature 74 — Sound. International WELL Building Institute (IWBI), 2020. Available at wellcertified.com. Parts L01–L07 as described above.
ISO 3382-2:2008 — Measurement of room acoustic parameters. Part 2: Reverberation time in ordinary rooms. Required measurement method for L07.
ISO 16283-1:2014 — Field measurement of sound insulation in buildings. Part 1: Airborne sound insulation. Required for L06 field measurements.
IEC 61672-1:2013 — Electroacoustics — Sound level meters. Class 1 meters required for all WELL measurements.
ISO 1996-1:2016 — Acoustics — Description, measurement and assessment of environmental noise. Methodology for exterior noise assessment in L01 and L02.
For a deeper analysis of Feature 74's three most common failure modes, see WELL Acoustic Certification: What Goes Wrong and Why. For a cost breakdown of WELL acoustic compliance, see WELL Certification Cost: The Acoustic Component.