How to Specify Biophilic Acoustic Wall Systems in 5 Steps
A repeatable decision framework for architects, acousticians, and consultants - from acoustic brief to installed system. Covers performance data, fire compliance, and certification mapping.
Table of contents
#Why acoustic specification for biophilic systems is different
Specifying biophilic acoustic solutions should be straightforward. In practice, it rarely is.
Project teams face a consistent set of obstacles: acoustic data that was tested under conditions that don't match the project, fire classifications that apply to isolated materials but not to installed assemblies, sustainability claims that don't map to any recognized certification framework, and product documentation that focuses on aesthetics while leaving performance unsubstantiated.
The result is a specification process driven by assumption rather than evidence. Materials are selected for how they look, not how they perform. Fire safety is addressed late - sometimes after procurement. Certification contributions are discovered retroactively, or missed entirely.
This article offers a different approach. A structured, 5-step decision framework that moves from the acoustic brief to the complete system specification - with fire compliance, certification mapping, and documentation built into the process from the start.
#The 5-step specification framework
From acoustic brief to installed system
Each step builds on the previous one. Skipping a step - or reversing the order - is where most specification issues originate. Selecting a product before defining the acoustic target leads to solutions that look right but underperform. Addressing fire compliance after procurement leads to costly substitutions or project delays.
The framework applies to any biophilic acoustic material. This article illustrates each step with Greenmood's preserved systems - Ball Moss, Velvet Leaf, Forest, Reindeer Moss, and Cork Acoustic Tiles - where acoustic, fire, and sustainability data is available for each step.
How to define acoustic targets for interior spaces
Every acoustic specification begins with a question: what does this space need to sound like?
The answer depends on how the space will be used, how many people will occupy it, what surfaces already exist, and what level of speech clarity or acoustic comfort is expected.
The two metrics that matter most for interior acoustic comfort:
- Reverberation Time (RT60) - How long sound persists in a space after the source stops. For open offices, the target is typically 0.5–0.8 seconds. For meeting rooms, 0.4–0.6 seconds. For hospitality lobbies, acceptable ranges are wider but still require control.
- Background Noise Level - Measured in dB(A). Most offices exceed 45 dB(A), which is above the threshold for sustained concentration. Reducing reverberation directly impacts perceived noise, even when the source volume remains constant.
Before selecting any material, the project team should establish:
A common rule of thumb: in a typical open-plan office of 200 m², reducing RT60 from 1.2 seconds to 0.6 seconds may require approximately 60–80 m² of absorptive surface with an NRC above 0.65, depending on existing finishes and room geometry. This number should be validated by an acoustician during design development, but it provides a useful starting point for feasibility conversations.
This step is not about choosing a product. It is about defining what the product must achieve.
Choosing between moss, cork, and preserved foliage for acoustic performance
Once the acoustic target is defined, the next decision is which material family best addresses both the performance requirement and the design intent.
In biophilic acoustic design, three material families are most commonly specified: preserved moss, preserved foliage, and natural cork. Each absorbs sound at different rates, at different frequency profiles, and each suits different project contexts.
| Material | NRC | ISO Class | Best application |
|---|---|---|---|
| Ball Moss | 0.73 | D (ISO 11654) | Large surfaces, ceilings, open offices, atriums - highest absorption in the collection |
| Velvet Leaf | 0.65 | C (ISO 11654) | Feature walls, lounges, corridors, hospitality - mid-range absorption with visual depth |
| Cork Acoustic Tiles (Parenthèse, Sillon, Brickx, Morse) |
Tested ISO 11654 | Tested | Meeting rooms, branded spaces, modular walls - designed by Alain Gilles in four architectural patterns |
| Reindeer Moss | System-level | Part of system | Background textures, mixed compositions - used in Forest and custom combinations |
The selection depends on three factors:
Left to right: Ball Moss (NRC 0.73) · Velvet Leaf (NRC 0.65) · Cork Acoustic Tiles - three material families, each suited to different acoustic and design requirements.
- Performance priority. If the primary goal is maximum sound absorption per square meter, Ball Moss at NRC 0.73 delivers the highest absorption. For moderate absorption with distinctive visual impact, Velvet Leaf at NRC 0.65 provides strong mid-frequency performance with visual complexity. For modular applications, Cork Acoustic Tiles combine pattern flexibility with tested acoustic data.
- Design language. Cork tiles offer four architectural patterns - Parenthèse, Sillon, Brickx, and Morse - designed by Alain Gilles, where acoustic performance integrates into a deliberate design vocabulary. Preserved moss and Forest compositions offer organic, textural qualities that cannot be replicated with synthetic alternatives.
Cork Acoustic Tiles - four architectural patterns by Alain Gilles: Parenthèse, Sillon, Brickx, and Morse. Modular wall systems where acoustic performance meets design intent.
- Application context. Ceilings and large open walls favour Ball Moss for uniform absorption. Branded environments and meeting rooms favour Cork for pattern control. Mixed compositions using multiple foliage types - as in the Forest collection - create visual depth while maintaining system-level acoustic integrity.
At this stage, the specification should include the material family, the target surface area, and the expected NRC contribution - validated against the acoustic target established in Step 1.
Fire classification requirements for preserved green wall systems
Fire compliance should be confirmed before a product enters the specification - not after procurement. This is the step most often deferred, and the one most likely to cause project delays or forced substitutions.
The critical distinction, covered in depth in our fire safety guidance, is between material-level testing and system-level testing. A fire test on a flat moss sample does not represent the performance of a complete wall assembly with backing, adhesive, frame, and mounting.
Four questions to verify fire documentation:
Greenmood fire classifications (system-level):
| Standard | Classification | Region | Basis |
|---|---|---|---|
| EN 13501-1 | B-S2-d0 | EU / UK | Complete assembly tested |
| ASTM E84 | FSI 0 / SDI 15 | US / North America | Complete assembly tested |
These classifications apply to the installed system - not to individual material samples. If any of these conditions are unclear for a product under consideration, the specification is not ready to proceed.
How biophilic acoustic products contribute to LEED v5, BREEAM, and WELL credits
Many projects today pursue environmental or wellness certification - LEED, BREEAM, WELL, or regional equivalents. Biophilic acoustic solutions can contribute to multiple credit categories when properly documented, but this contribution needs to be identified at specification stage, not retroactively.
| Credit category | How biophilic acoustics contribute | Required documentation |
|---|---|---|
| Indoor Environmental Quality (LEED EQ / BREEAM Hea / WELL Sound) |
Certified sound absorption data (Ball Moss NRC 0.73, Velvet Leaf NRC 0.65). Contribution to RT60 reduction. Improved speech clarity and occupant comfort. | NRC test reports (ISO 11654). In-situ measurement data when available. |
| Materials & Resources (LEED MR / BREEAM Mat) |
Natural, preserved materials with traceable sourcing. Extended lifecycle with zero replacement. No synthetic components in primary foliage. Cork bark harvested without cutting trees (renewable every 9 years). | Material sourcing documentation. Lifecycle data. Preservation process description. |
| Biophilic Quality (LEED v5 Connecting with Nature / WELL Mind) |
Direct, non-representational connection to nature using real plant material. Sensory richness and visual complexity. Alignment with 12 biophilic attributes recognized by LEED v5. | Product composition documentation. Biophilic attribute mapping. Installation photography. |
The operational advantage of preserved systems in certification contexts is significant. Unlike living installations, preserved walls require no irrigation logs, no plant replacement records, no seasonal maintenance schedules, and no ongoing horticultural management documentation. This simplifies the most time-consuming element of certification: operational compliance over the building lifecycle.
What a complete biophilic wall system specification includes
The final step is where most specification documents fall short. They name a product - "preserved moss wall" - without defining the system: the backing, the mounting, the substrate interface, the edge conditions, the maintenance protocol (or absence of one).
A complete specification for a biophilic acoustic system includes:
When a green wall is specified as a system - with acoustic data, fire classification, dimensional precision, and certification mapping - it stops being a decorative choice and becomes a documented, defensible architectural element.
System-level specification in practice: custom-fabricated panels, precise dimensional fit, and wrap corners that follow the architecture - not generic flat panels trimmed on site.
#In practice: the Wisecom project, Paris
Measured acoustic improvement in a real workspace
Wisecom - Paris, France
For the Wisecom project in Paris, acoustic comfort was the primary design driver. Noise levels across the open workspace were affecting focus, speech clarity, and day-to-day usability. The brief required reducing reverberation without compartmentalizing the space - no partitions, no layout changes.
The solution, designed and delivered by Greenmood France, combined two complementary interventions:
- Preserved Ball Moss walls - contributing to broadband sound absorption while introducing a strong natural, biophilic dimension to the interior.
- Suspended acoustic circles above workstations - improving reverberation control precisely where it matters most, while visually structuring the open space without physical barriers.
Wisecom, Paris - Ball Moss walls combined with suspended acoustic circles. Measured result: −10 dB across the open workspace.
The measured result - a 10 dB reduction across the workspace - represents a substantial improvement in acoustic comfort, with a direct impact on concentration, communication clarity, and perceived noise levels.
This project illustrates the framework in action: an acoustic target was defined (reduce reverberation in open workspace), materials were selected for performance and design fit (Ball Moss walls + suspended elements), fire compliance was verified for the French market, and the solution was specified and installed as a complete system.
#Acoustic performance data: Greenmood product reference
| Product | NRC | ISO Class | Fire (EU) | Fire (US) | Maintenance |
|---|---|---|---|---|---|
| Ball Moss | 0.73 | D | B-S2-d0 | FSI 0 / SDI 15 | None |
| Velvet Leaf | 0.65 | C | B-S2-d0 | FSI 0 / SDI 15 | None |
| Sparse Forest (mixed composition) |
System-level | System-level | B-S2-d0 | FSI 0 / SDI 15 | None |
| Reindeer Moss | System-level | System-level | B-S2-d0 | FSI 0 / SDI 15 | None |
| Cork Acoustic Tiles (Parenthèse · Sillon · Brickx · Morse) |
Tested ISO 11654 | Tested | B-S2-d0 | FSI 0 / SDI 15 | None |
Preserved moss texture detail - the variation in density, depth, and surface structure across foliage types directly influences acoustic absorption characteristics.
#Specification scenarios by space type
What to specify for open offices, meeting rooms, and lobbies
| Space type | Target RT60 | Recommended product | Indicative surface | Notes |
|---|---|---|---|---|
| Open-plan office (200 m²) |
0.5–0.8 s | Ball Moss walls + suspended acoustic elements | 60–80 m² absorptive surface (NRC ≥ 0.65) | Combine wall treatment with ceiling elements for best broadband absorption. See Wisecom case study for a measured example (−10 dB). |
| Meeting room (30 m²) |
0.4–0.6 s | Cork Tiles (Sillon or Parenthèse) or Velvet Leaf feature wall | 8–14 m² absorptive surface | Cork tiles offer pattern control suited to branded or formal environments. Velvet Leaf provides a more organic alternative. Speech clarity is the priority metric. |
| Lobby / reception (100–300 m²) |
0.8–1.2 s | Forest composition or large-scale Ball Moss feature | Variable - depends on volume and ceiling height | High-volume spaces require acoustic modeling. Forest compositions provide visual impact at scale while contributing system-level absorption. Custom fabrication (wrap corners, non-standard panels) often required. |
These are indicative starting points. Greenmood provides project-specific acoustic estimates during the specification consultation process, accounting for room geometry, existing finishes, and target performance levels.
Biophilic acoustic treatment integrated into a professional workspace - the specification scenarios above translate directly into installations like this.
#Documentation provided at each project stage
| Project stage | Available from Greenmood |
|---|---|
| Concept / briefing | Product sample box. Configurator access. Preliminary acoustic estimates based on room type and surface area. |
| Schematic design | Technical data sheets per product. NRC and fire classification summaries. Material composition descriptions. |
| Design development | Full acoustic test reports (ISO 11654). Fire test reports (EN 13501-1 / ASTM E84). LEED Support Pack with credit mapping. CAD and dimensional drawings. |
| Construction documents | Panel-by-panel dimensional specifications. Installation guides. Custom fabrication documentation (wrap corners, non-standard panels). |
| Post-installation | As-built documentation. Maintenance protocol (confirming zero ongoing maintenance). Photography for certification submissions. |
#Specification checklist
Verify before the product enters the specification document
#Frequently asked questions
What NRC rating do I need for an open-plan office?
For open-plan offices targeting an RT60 of 0.5–0.8 seconds, specify materials with NRC 0.65 or higher. Ball Moss (NRC 0.73) and Velvet Leaf (NRC 0.65) both meet this threshold. The required surface area depends on room geometry and existing finishes - as a starting point, plan for 30–40% of the ceiling or wall area to be treated with absorptive material.
Do preserved moss walls require fire testing?
Yes. Preserved moss walls must be fire-tested as complete assemblies - not just as isolated material samples. A test on a flat moss sample does not represent the fire behavior of the installed system. Greenmood systems are classified B-S2-d0 under EN 13501-1 (EU/UK) and FSI 0 / SDI 15 under ASTM E84 (US), based on system-level testing. Full test reports are available on our downloads page.
Can biophilic acoustic products contribute to LEED v5 credits?
Yes. Preserved biophilic systems can contribute to multiple LEED v5 credit categories simultaneously: Indoor Environmental Quality (acoustic performance), Materials & Resources (natural sourcing, extended lifecycle), and the new Connecting with Nature biophilic quality credit. A LEED Support Pack is available with detailed credit mapping for consultants.
What is the difference between sound absorption and sound insulation?
Sound absorption reduces reverberation within a space - it is measured by NRC and improves speech clarity and acoustic comfort. Sound insulation blocks sound transmission between spaces - it is measured by STC. Preserved moss and cork walls provide sound absorption. They significantly improve acoustic conditions inside a room, but they are not designed to prevent sound from traveling to adjacent spaces. For more detail, see our acoustic performance guide.
How much preserved moss wall do I need to improve acoustics?
As a guideline, a 200 m² open office may require 60–80 m² of absorptive surface with NRC above 0.65 to reduce RT60 from 1.2 seconds to 0.6 seconds. The exact requirement depends on existing finishes, room geometry, and ceiling height. In the Wisecom project, combining Ball Moss walls with suspended acoustic elements achieved a measured −10 dB reduction. Greenmood provides project-specific acoustic estimates during the specification process.
Do preserved green walls need ongoing maintenance?
No. Preserved green wall systems require zero irrigation, zero plant replacement, and zero ongoing horticultural maintenance. This also simplifies certification documentation - no irrigation logs, no seasonal maintenance records, no replacement schedules. The system performs as installed, for the expected lifespan, with no operational overhead.
#Related A&D guidance
This article consolidates specification thinking from three companion articles, each covering one dimension of the framework in depth:
Final takeaway
Biophilic acoustic solutions perform best when they are specified as systems - with acoustic targets, fire compliance, certification mapping, and documentation built into the process from the start. The framework is simple. The discipline to follow it is what separates specification from selection.
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