TL;DR — 30 Minutes to WELL Acoustic Confidence
WELL v2 Feature 74 (Sound) is the certification component that causes the most project delays — not because the acoustic requirements are difficult, but because teams do not check compliance early enough. The typical failure mode is discovering at the documentation submission stage that three meeting rooms exceed the RT60 limit and two open-plan zones fail the background noise criterion, triggering a design revision cycle that delays certification by 8–12 weeks. This guide walks through a 30-minute AcousPlan workflow that checks every acoustic parameter in Feature 74 at the design stage, generates the pre-certification evidence package, and identifies problems while they can still be fixed for free — by changing a material specification rather than retrofitting a completed room.
The Story: 12 Weeks Lost to a Missing Check
A 4,500 m² commercial office fit-out in Singapore pursued WELL Gold certification. The acoustic consultant produced a compliance report at tender stage showing all spaces meeting Feature 74. During construction, the contractor substituted the specified ceiling tiles (NRC 0.90) with a "similar" product (NRC 0.70) — a common value engineering decision. Nobody re-checked the acoustics. At the WELL Performance Verification stage, four of nine tested rooms failed RT60 limits. The remediation required removing the installed ceiling tiles and replacing them, at a cost of $38,000 and a 12-week programme delay. A 10-minute recalculation after the substitution would have flagged the problem immediately.
The WELL v2 Feature 74 Acoustic Requirements
Feature 74 covers five preconditions and optimisations. The table below summarises the acoustic parameters relevant to the AcousPlan workflow:
| WELL Feature 74 Part | Parameter | Typical Target | AcousPlan Coverage |
|---|---|---|---|
| L07 Sound Mapping | Acoustic zoning plan | Qualitative | Room type assignment |
| L08 Exterior Noise | Facade insulation (Rw) | Rw 35-45 dB (by exposure) | Sound insulation calc |
| L09 Internal Noise | Background noise level | NC 25-40 (by space type) | Noise criteria check |
| L10 Reverberation Time | RT60 at 500, 1000, 2000 Hz | 0.4-0.6 s (by type) | Full RT60 calculation |
| L11 Sound Masking | Masking spectrum + level | 40-48 dBA broadband | Masking design tool |
The 30-Minute Workflow: Step by Step
Minutes 0–5: Create Project and Define Rooms
Open AcousPlan and create a new project. For each distinct acoustic zone, create a room entry with:
- Room name and type (select from WELL-compatible room types: open office, enclosed office, meeting room, classroom, etc.)
- Dimensions (length, width, height) or import from your BIM model
- Occupancy count (affects furnished absorption calculation)
Tip: Use the "Duplicate Room" function for similar spaces — duplicate a standard 8-person meeting room and adjust only the dimensions for each instance.
Minutes 5–12: Assign Materials and Verify RT60
For each room, assign the specified materials to ceiling, floor, and wall surfaces using AcousPlan's material library. The calculator automatically:
- Retrieves ISO 354-tested octave-band absorption coefficients
- Calculates RT60 at 125, 250, 500, 1000, 2000, and 4000 Hz using Sabine or Eyring (auto-selected based on average absorption)
- Compares results against WELL Feature 74 L10 RT60 limits for the selected room type
- Flags any frequency band that exceeds the target
| Room Type | WELL L10 RT60 Target | Typical Untreated RT60 | Treatment Needed? |
|---|---|---|---|
| Open office (per workstation zone) | ≤ 0.5 s | 0.8–1.2 s | Yes — ceiling + partial wall |
| Enclosed meeting room (<50 m³) | ≤ 0.6 s | 1.0–1.5 s | Yes — ceiling minimum |
| Enclosed office | ≤ 0.6 s | 0.9–1.3 s | Yes — ceiling minimum |
| Reception / lobby | ≤ 0.8 s | 1.5–3.0 s | Yes — ceiling + wall + furniture |
| Breakout / cafe | ≤ 0.7 s | 1.2–2.0 s | Yes — ceiling + soft furnishing |
Minutes 12–18: Check Background Noise (L09)
Switch to the noise criteria tab in AcousPlan. For each room, enter:
- HVAC system type (VAV, FCU, split system, natural ventilation)
- Duct dimensions and air velocity (if known)
- Distance from air handling unit
| Room Type | WELL L09 Max Background Noise |
|---|---|
| Open office | NC 40 / RC 40 |
| Enclosed meeting room | NC 30 / RC 30 |
| Enclosed office | NC 30 / RC 30 |
| Conference room (>20 people) | NC 25 / RC 25(N) |
| Focus room | NC 30 / RC 30 |
Calculate Now: Use AcousPlan's WELL Feature 74 calculator to check RT60 and noise criteria compliance for all your project rooms simultaneously — the tool automatically applies WELL-specific targets.
Minutes 18–22: Address Any Failures
If any room fails an RT60 or noise criterion, AcousPlan's auto-solve function identifies the minimum material changes needed to achieve compliance. Typical fixes:
- RT60 too high: Upgrade ceiling tile from NRC 0.70 to NRC 0.85, or add wall absorbers to one surface
- Background noise too high: Add duct silencer, reduce air velocity, or increase distance from AHU to diffuser
- Both: Often solved together by upgrading the ceiling (absorption helps RT60) and specifying lower-noise diffusers
Minutes 22–28: Generate the Pre-Certification Report
Export the WELL acoustic compliance report from AcousPlan. The report includes:
- Project summary with room schedule
- RT60 calculation results at all octave bands per room, compared against WELL L10 targets
- Background noise assessment per room, compared against WELL L09 targets
- Material schedule with ISO 354 test references
- Sound mapping plan (L07) showing acoustic zone assignments
- Compliance summary table with pass/fail status for each Feature 74 component
Minutes 28–30: Review and Submit
Review the compliance summary. Verify that every room shows "Pass" for L10 (RT60) and L09 (Background Noise). If any room shows "Marginal" (within 10% of the limit), consider adding a safety margin — construction tolerances and material substitutions during procurement can erode thin margins.
Save the project for future reference. When the contractor proposes material substitutions during construction, re-run the calculation with the proposed product to verify compliance is maintained — the 10-minute check that would have saved the Singapore project $38,000.
Common WELL Acoustic Certification Mistakes
Mistake 1: Checking only enclosed rooms. WELL Feature 74 L10 applies to open-plan areas too, not just meeting rooms. The open-plan RT60 target is often stricter (≤ 0.5 s) than the enclosed room target (≤ 0.6 s).
Mistake 2: Using NRC instead of octave-band data. WELL specifies RT60 at individual frequencies (500, 1000, 2000 Hz). NRC-based calculations cannot verify compliance at each frequency.
Mistake 3: Forgetting to re-check after material substitutions. Value engineering during construction is the primary cause of WELL acoustic failures. Every substitution must be re-checked.
Mistake 4: Ignoring the masking requirement. WELL L11 (Sound Masking) requires a uniform broadband spectrum at 40–48 dBA in open-plan spaces. If the project includes open-plan zones, masking system design must be part of the acoustic submission.
Mistake 5: Submitting predictions without measurement protocol. WELL expects a post-construction measurement plan. Include the measurement methodology (ISO 3382-2 for RT60, ISO 16283 for insulation) in your pre-certification documentation.
Summary
WELL v2 Feature 74 acoustic compliance is not intrinsically difficult — the RT60 and noise criteria targets are achievable with standard commercial acoustic products. The challenge is checking early, checking correctly, and re-checking after changes. The 30-minute AcousPlan workflow puts all five Feature 74 acoustic components through a rigorous calculation at the design stage, when fixing a problem costs nothing more than a specification line item change.
Do not wait for the WELL Performance Testing Agent to find problems that a 30-minute design check would have caught. Start your WELL acoustic pre-certification now.