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Acoustic Performance & Carbon Footprint in CLT Floor Design
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What Test Campaigns Reveal about Floor Build-up Choices
Cross-laminated timber (CLT) is increasingly used in residential and mixed-use buildings due to its structural efficiency and lower embodied carbon. However, achieving strong acoustic performance in lightweight timber structures remains a key design challenge.
To better understand how floor build-up choices influence performance, CDM Stravitec conducted a series of laboratory test campaigns on floating floor systems installed on CLT slabs. These tests evaluate how different configurations affect both airborne and impact sound insulation.
Today, this dataset can be extended further by integrating Environmental Product Declaration (EPD) data - allowing designers to assess not only acoustic performance, but also the carbon footprint of different floor solutions.
Adding a New Dimension: Carbon Footprint
Today, results can also be evaluated from another perspective: the carbon footprint of different floor assemblies.
EPDs are now available for Stravifloor Deck and Stravifloor Channel. These verified datasets make it possible to estimate the embodied carbon associated with different floor configurations.
By combining the acoustic performance results from our CLT test campaigns with EPD data, designers can now evaluate how floor system choices influence both:
- vibration and sound insulation performance
- environmental impact
This dual perspective allows project teams to better understand the trade-offs between acoustic performance and embodied carbon when designing floor assemblies in timber buildings.
Comparing Different Stravifloor Build-ups on Cross-Laminated Timber
The analysis compares several floating floor solutions installed on CLT slabs. The results highlight how changes in board composition and build-up height influence both acoustic performance and carbon footprint.
| Stravifloor Deck(1) | Stravifloor Channel w/ CLD (2) | Stravifloor Channel w/ cement & wooden boards | Stravifloor Channel w/ cement & wooden boards and overheight | Stravifloor Channel w/ wooden boards and overheight | |
|---|---|---|---|---|---|
| Build-up height [mm (in)] |
100 (3.94) |
93 (3.60) |
100.5 (3.96) |
136.5 (5.37) |
118 (4.65) |
| STC | 65 | 64 | 63 | 67 | 66 |
| IIC | 55 | 55 | 56 | 63 | 57 |
| A1-A3 GWP (with carbon storage) [kg CO2eq/m² (kg CO₂eq/ft²)](3) | 33.5 (3.1) |
-21.1 (-1.9) |
-8.3 (-0.7) |
20.5 (1.9) |
-23.2 (-2.1) |
| A1-A3 GWP (without carbon storage) [kg CO2eq/m²](3) |
33.5 (3.1) |
14.1 (1.3) |
21.0 (1.9) |
21.6 (2.0) |
13.1 (1.2) |
| A1-A3 GWP (with carbon storage) - incl. CLT slab [kg CO2eq/m²](3) |
-84.1 (-7.8) |
-138.8 (-12.9) |
-126.1 (-11.7) |
-97.2 (-9.0) |
-140.9 (-13.1) |
| GWP (A1-A3) (without carbon storage) - incl. CLT slab [kg CO2eq/m²](3) |
50.6 (4.7) |
31.2 (2.9) |
38.1 (3.5) |
38.7 (3.6) |
30.2 (2.8) |
(1) Considering cement type III.
(2) Constrained Layer Damping.
(3) GWP (Global Warming Potential)
Values are based on EPDs or, where unavailable, on industry-average Benelux/French datasets.
Takeaways
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Interpreting the Results: Acoustic Performance Across Metrics
The comparison highlights how different floor build-ups influence acoustic performance across multiple indicators.
- Airborne sound insulation, expressed through STC values, follows a consistent trend across configurations. Solutions with increased mass and build-up height - such as the Stravifloor Channel with overheight and mixed boards - achieve the highest performance (STC 67), indicating strong resistance to airborne noise transmission.
- Impact sound insulation, reflected in IIC values, shows more pronounced variation. The same high-mass configuration reaches IIC 63, demonstrating significantly improved vibration isolation compared to lighter systems.
For designers, this classification translates technical results into clear performance targets aligned with regulatory and comfort expectations, making it easier to evaluate the suitability of each build-up in real projects.
-
Influence of Build-up Height and System Mass
The results show a clear relationship between system mass, build-up height and acoustic performance.
Configurations with increased mass and additional height, such as the Stravifloor Channel solution with overheight and combined cement and wooden boards, achieve the highest performance across multiple indicators. The added mass improves airborne sound insulation, while the increased system depth enhances vibration isolation by reducing structural transmission paths.
This combination results in improved performance for both airborne and impact noise (STC, IIC respectively).
However, these improvements are achieved through additional material layers and increased system thickness. As a result, design choices that optimise acoustic performance in this way also tend to influence the overall material use and environmental impact of the floor assembly. -
Lower Carbon Dry Floor Solutions
Lighter dry screed configurations demonstrate that it is possible to reduce embodied carbon while maintaining solid acoustic performance levels.
Solutions such as the Stravifloor Channel with CLD technique or configurations using only wooden boards achieve competitive results across airborne and impact sound indicators, while significantly lowering the associated carbon footprint compared to heavier reference solutions.
Although these systems generally perform at a lower level than high-mass configurations, particularly in impact sound insulation and corresponding IIC values, they remain within acceptable ranges for many residential applications.
These results highlight that optimised dry floor solutions can offer a balanced approach, reducing material use and embodied carbon without compromising essential acoustic requirements. -
Understanding the Acoustic–Carbon Trade-off
The comparison illustrates a key design consideration in CLT floor systems: acoustic performance and carbon optimisation do not necessarily align.
Configurations that achieve the highest acoustic performance, reflected across STC and IIC, typically rely on increased system mass and build-up height. This leads to higher material use and, consequently, a greater embodied carbon impact. Conversely, lighter systems reduce material intensity and carbon footprint, but may result in lower performance in certain acoustic indicators, particularly those related to impact sound insulation.
By combining measured acoustic data with EPD-based carbon calculations, designers can evaluate these trade-offs more effectively. Rather than optimising for a single parameter, this approach supports more informed decisions that balance acoustic comfort requirements with environmental performance targets. -
Supporting Better Design Decisions in Mass Timber and Other Sustainable Projects
Bringing together measured acoustic performance across multiple indicators, STC and IIC, with verified carbon data provides a more complete basis for decision-making in CLT floor design, while also supporting alignment with building certification frameworks such as BREEAM and LEED. Rather than evaluating individual parameters in isolation, project teams can better understand how build-up choices influence both acoustic comfort and embodied carbon.
This combined approach enables more informed design strategies from the early stages of a project, where floor configurations can be optimised to meet performance requirements, reduce environmental impact, and contribute to certification targets.
Technical Bulletin: Stravifloor on CLT Slabs
This Technical bulletin summarises the key findings of an extensive test campaign studying the acoustical performance (airborne sound reduction and impact noise isolation) of lightweight Stravifloor solutions in combination with cross-laminated timber slabs.