Understanding how glass type influences the acoustic performance of glass partitions

Acoustic test evidence should therefore relate to a clearly defined and tested system configuration. The test certificate should identify the system, glass specification and test method, allowing the stated performance to be understood and assessed accurately.

It is also important to recognise that laboratory test results relate to the complete tested specimen. The performance achieved on site may be affected by installation quality, interfaces with adjoining construction, doors, penetrations and sound travelling through surrounding elements.

The type and thickness of glass must be considered alongside the acoustic rating required for the complete partition system.

For example, the Optima 117 single-glazed system has been tested with different glass specifications, achieving the following laboratory ratings:

• 12mm toughened glass in a single-glazed, multi-module screen: Rw 33dB
  Test reference: 542-434
• 14.8mm acoustic laminated glass in a single-glazed, multi-module screen: Rw40dB
  Test reference: 438126/01/P004

Where higher acoustic ratings are required, a double-glazed system may be appropriate. The Revolution 100 double-glazed system can accommodate different combinations of glass type and thickness, including:

• 12mm toughened glass and 12.8mm acoustic laminated glass: Rw 48dB
  Test reference: 2151-1845
• Two panes of 12.8mm acoustic laminated glass: Rw 51dB
  Test reference: 2151-1848

These results demonstrate why the performance of acoustic glass partitions should not be judged solely by whether a system is single or double glazed. The complete tested configuration, including the glass build-up, must be considered.

Acoustic performance is only one part of glass selection. The intended application, safety requirements, loading conditions, fixing method and need for drilled or cut openings must also be considered.

Different safety glass types offer different characteristics, making some more suitable than others for particular applications.

The following sections explain the glass types commonly used within Optima partition systems and where each may be appropriate.

Toughened glass

Standard: BS EN 12150
Annealed glass that has been thermally treated to give it much greater impact resistance: typically, seven times greater. Toughened glass satisfies BS6206 in that it breaks safely, shattering into equally sized ‘dice’. Drilling or clamping glass is only recommended with Toughened, for example, when used for accommodating door furniture.

It is important to note that the toughening process stimulates Nickel Sulphide (NiS), known as ‘inclusions’, which occurs naturally in float glass. The presence of these inclusions can, over time, although very rare, induce a spontaneous fracture of a toughened glass panel. Whilst all glass manufacturers and processors take all practicable steps to ensure glass is inclusion-free, it is not possible to guarantee the absence of nickel sulphide inclusions.

Heat soaked toughened glass

Standard: BS EN 14179
To significantly reduce the risk of NiS induced spontaneous failure, toughened glass panels are sometimes subjected to an additional process known as heat soak testing. Although not providing a 100% guarantee, this process can reveal the presence of NiS inclusions. It is a destructive test, designed to break any panel that is at risk. In order to ensure complete customer confidence in the safety of glass, it is company policy to heat soak all toughened glass.

Laminated glass

Standard: BS EN ISO 12543
Producing Laminated glass requires bonding two layers of annealed glass either side of a PolyVinyl Butyral (PVB) Interlayer. With the intention of categorising our product as a class A safety glass, the PVB interlayer must be not less than 0.76mm thick and achieve safe breakage by the interlayer holding the fractured panel together. When not needing to drill or cut the glass, we recommend the use of laminated glass for partitions.

Acoustic laminated glass

Standard: BS EN ISO 12543
We produce Acoustic laminated glass the same way we produce regular laminated glass. However, it utilises a specially formulated acoustic PVB interlayer to achieve significantly better acoustic properties.

Toughened laminated glass

Standards: BS EN 12150 (Toughened) and BS EN 12543 (Laminated)
This type of glass combines the benefits of both toughened and laminated glass and would typically involve a 1.5mm PVB interlayer. Because it has the additional benefit of lamination, the glass would not normally require the additional process of heat soaking. Toughened laminate glass, commonly specified for glass screens adjacent to a significant change in level (e.g. an atrium) and where there is the potential for significant crowd loading as defined in BS 6180 and BS 6399.

Annealed glass (unprocessed float glass)

We do not use Annealed glass in its basic, unprocessed form due to the fact that it is not categorised as safety glass.

The correct specification for acoustic glass partitions depends on both the desired sound reduction and the way the glass will be used within the building.

Single-glazed partitions requiring enhanced acoustic performance

Architects frequently specify laminated glass for partitions because of its breakage behaviour and the ability to vary the interlayer to support acoustic, privacy, security or decorative requirements.

On the CMS project, a high acoustic rating was required from a single-glazed system. A 12.8mm acoustic laminated glass specification was therefore selected to support the project’s acoustic requirements within the chosen system configuration.

Full-height partitions acting as guarding

Where a full-height glass partition is positioned beside a level change, it may also need to fulfil a guarding function.

At JP Morgan, the Revolution double-glazed system incorporated a combination of 17.5mm toughened laminated glass and 12.8mm laminated glass. The glass specification was selected to address the relevant safety requirements and design loads while forming part of the complete double-glazed partition system.

Glass is only one part of acoustic performance

Selecting acoustic laminated glass does not, by itself, establish the performance of an acoustic glass partition.

The final result depends on the complete system, including:

• The glass type and thickness
• The number of panes
• The cavity between the panes
• The framing and seals
• The door specification
• Junctions with walls, ceilings and floors
• Installation quality
• Flanking sound paths through surrounding construction

For this reason, acoustic ratings should be linked to the precise configuration that was tested. Substituting the glass, changing the system arrangement or introducing different interfaces may alter the performance.

Different glass types and thicknesses can be used within acoustic glass partitions to address acoustic, safety, loading and application requirements.

Toughened glass may be appropriate where drilling or clamping is necessary. Laminated glass offers post-breakage retention and flexibility through different interlayer specifications. Acoustic laminated glass can provide improved sound reduction, while toughened laminated glass may be required where impact resistance, guarding or higher design loads must also be considered.

The required acoustic rating should always be assessed against test evidence for the complete partition configuration, not the glass in isolation.

For support selecting the appropriate glass and partition configuration for your project, speak to Optima’s technical team.