Acoustic movable walls: Rw insulation 38 to 55 dB
The NF S 31-080 standard sets Rw >= 38 dB for executive rooms
Catalogue Rw 55 dB = field DnT,A 47-50 dB: 5 to 8 dB vanish into the flanks, the plenum and the raised floor. For executive rooms, the regulatory threshold is set at Rw >= 38 dB, but the real contractual performance is measured as DnT,A on site, once lateral transmissions are taken into account. The acoustic office movable wall divides a 200 m² room into two independent spaces in under 8 minutes, for a budget generally between 850 and 2,200 euros/m² depending on the acoustic performance targeted and the complexity of the site. For the architect and the building engineering firm, the decision is not to choose a catalogue Rw: it is to guarantee a contractual DnT,A once lateral transmissions, the storage parking and article R4216-2 on escape routes have been taken into account. Kytom has been involved in this type of trade-off since 2006, with internal feedback from 1200+ projects in France and Spain. Selecting the Rw category mobilises three variables: the surface mass of the panels (45 to 65 kg/m²), the ceiling height (up to 6 metres) and the performance of the adjacent elements.
An acoustic movable wall differs from a removable partition in its ability to be deployed several times a week while guaranteeing reproducible insulation. The hierarchy of requirements in commercial offices is established as follows:
| Usage level | Target Rw | Fixed partition equivalent | Application case |
|---|---|---|---|
| Standard confidentiality | >= 32 dB | 72/48 single facing | Closed offices |
| Sensitive meeting room | >= 38 dB | 98/48 single facing | Management, HR |
| Training / open space | 45 to 48 dB | 98/48 double facing | Training rooms |
| Executive committee / event | 52 to 55 dB | 100 mm masonry partition | Modular plenary rooms |
Our reading differs from common practice on one precise point: the industry communicates on laboratory Rw, but it is the in situ DnT,A that prevails at handover. Under standard conditions, the gap between the catalogue Rw and the DnT,A measured in situ at handover typically lies between -3 and -5 dB, and can reach -8 dB when the flanks are not treated upstream. Specifying Rw 52 dB to achieve executive committee comfort at 47 dB DnT,A is the rule, not the exception.
The panels are 100 to 110 mm thick, double-skin with an absorbent core (mineral wool 60 to 80 kg/m³). The telescopic upper and lower perimeter seals, deployed by crank or electric system, ensure acoustic sealing on all 4 sides. The 12-week lead time covers bespoke manufacturing, the reinforced top rail and deployment tests before handover.
The Kytom method sizes the movable wall in 4 phases over 12 weeks
Acoustic sizing follows a 4-phase sequence, proven on Kytom sites.
- Usage audit (weeks 1-2): survey of deployment frequency, of the activities on each side (training, committee, client event) and of the actual ceiling height.
- Choice of acoustic category (weeks 3-4): Rw 45 dB to separate training from open space, Rw 52 to 55 dB to isolate an executive committee from an amplified event space.
- Structural verification of the ceiling (weeks 5-6): the top rail supports 45 to 65 kg/m², i.e. 1.2 to 1.8 tonnes for 6 linear metres at 3 metres high. A support framework is installed in the suspended ceiling in most configurations, with a distribution slab compliant with the Eurocodes.
- In situ tests after installation (week 12): DnT,A measurement to validate the gap between laboratory performance (Rw) and field performance, generally a few decibels depending on lateral transmissions.
When the movable wall is not the right answer. Below 200 m² of room to be divided, or with fewer than 2 reconfigurations per week, the movable wall ceases to be cost-effective: its additional cost compared to a removable partition does not amortise over low-intensity use. Above 4 weekly reconfigurations on a small surface, it is the opposite: the removable partition shows its handling limits, and the movable wall becomes relevant again. For requirements above Rw 55 dB, or for daily use with EI60 fire-rating test certificate constraints, Kytom recommends a dry partition with a fire door, more robust and less costly to maintain.
The panels are made to measure with CE marking for the closure components. The testing phase conditions the contractual handover of sites above Rw 50 dB.
For the architect and the building engineering firm: integrate the movable wall from the sketch stage, not in package 7
The acoustic movable wall is treated by the profession as a finishing-trade item, delivered after the fact. On our recent sites, this sequence is the main source of acoustic underperformance observed at handover. For the architect and the building engineering firm, three decisions must be made at the sketch stage, not in the detailed design phase:
- Structural reinforcement of the ceiling: 1.2 to 1.8 tonnes suspended over 6 linear metres requires a primary framework sized according to the Eurocodes in force. Discovered late, this reinforcement mobilises several additional weeks of work and generates a significant addendum to the cost of the wall.
- Surface mass of the flanks: the perpendicular walls receiving the vertical seal must reach at least 40 kg/m². A standard 72/48 partition at 25 kg/m² loses 5 to 8 dB on the catalogue Rw. For the building engineering firm, the specification of the adjacent partition becomes an acoustic parameter, not merely an architectural choice.
- Storage parking for the panels: 1.5 to 3 linear metres of wall in lateral or perpendicular configuration. Integrated from the sketch stage, the parking blends into the circulation. Discovered in detailed design, it forces a reduction in the deployed length of 10 to 15%.
For the CFO and the Asset Manager. The ROI observed on this type of project generally lies between 4 and 7 years, thanks to the gain in usable floor area enabled by removing fixed partitions: a 120 m² plenary room can thus replace two 50 m² rooms separated by a 20 m² corridor, freeing up 50 m² that can be reassigned to workstations. The calculation mobilises a commercial rental cost of 350 to 750 euros/m²/year on the French office market and an average weekly utilisation rate of 3.2 deployments. Maintenance generally represents 2 to 4% of the initial CAPEX per year: annual greasing of the seals, top rail inspection, with no structural replacement before 8 to 12 years of use.
The investment cost ranges from 850 euros/m² (Rw 38 dB) to 2,200 euros/m² (Rw 55 dB with wood finishes and electric motorisation).
Frequently asked questions
What gap should be expected between catalogue Rw and DnT,A measured at handover?
Across 24 KYTOM projects measured at handover between 2022 and 2024, the recorded DnT,A typically falls 3 to 5 dB below the catalogue Rw, depending on the quality of flanking treatment (40 kg/m² minimum recommended) and perimeter junctions. The gap reaches -8 dB when lateral transmissions are not anticipated ahead of the works.
To put this solution into a broader strategy, explore our acoustic correction service.
