If you’ve read our recent blog posts you’ll know that a number of different factors come into play when specifying acoustic glass partitions. We’ve looked at how acoustic testing is carried out, how to ensure that your test certificate is credible, and how the acoustic performance of glass partitions is affected by factors on site.
It is also important to consider what glass type and thickness is needed in order to achieve the desired acoustic rating. For example, Optima’s 117 single glazed system has been tested using a variety of glass types and thicknesses, to achieve a range of acoustic ratings, such as:
12mm toughened glass in single glazed multi-module screen Rw33dB Test ref: 542-434
12.8mm acoustic laminated glass in single glazed multi-module screen Rw38dB Test ref: 542-432
For higher acoustic ratings, a double glazed system should be specified. Optima’s Revolution 100 double glazed system for example, can accommodate a range of glass types and thicknesses, such as:
12mm toughened glass + 12.8mm acoustic laminated glass Rw48dB Test ref: 2151-1845
2 x 12.8mm acoustic laminated glass Rw51dB Test ref: 2151-1848
When you’re selecting the glass thickness that best suits the required acoustic performance, you should also give consideration to how you’re applying the glass. That’s when it becomes important to understand the difference between the various glass types that could be specified, and when it’s most appropriate to use them.
All glass used in Optima’s glazed systems is class A safety glass as defined in BS6206. However, there are a number of glass types that fall into this category; some more appropriate than others in certain scenarios.
Annealed Glass (Unprocessed float glass)
Annealed glass in its basic, unprocessed form is not categorised as a safety glass and is therefore not suitable for use in partition systems or glass doors.
Standard: BS EN 12150
This is 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’. Toughened glass is the only glass recommended for use where drilling or clamping is required, 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 can be subjected to an additional process known as heat soak testing. Although not providing a 100% guarantee, this process is used to 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 Optima’s company policy to heat soak all toughened glass.
Standard: BS EN ISO 12543
Laminated glass is produced by bonding two layers of annealed glass either side of a PolyVinyl Butyral (PVB) Interlayer. In order to be categorised as a class A safety glass, the PVB interlayer must be not less than 0.76mm thick and safe breakage is achieved by the interlayer holding the fractured panel together. Optima recommends the use of laminated glass for partitions when no drilling or cutting of the glass is required.
Acoustic Laminated Glass
Standard: BS EN ISO 12543
Acoustic laminated glass is produced in the same way as the 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 should typically be 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.
Choosing a Glass Type for Partitions based on Application – Some Examples
Many architects choose to specify laminated glass in partitions, due to the safe nature of breakage and the added flexibility of being able to achieve different levels of sound control, privacy, security and decorative effects by varying the thickness and type of interlayer used. On the CMS project for example, a single glazed system with a high acoustic rating was required, so 12.8mm thick acoustic laminated glass was the perfect solution.
Where a full height glass partition is being used to protect a change in level it is said to be acting as guarding. This scenario occurred at JP Morgan, where our Revolution double glazed system was specified. We installed a combination of 17.5mm thick toughened laminated glass and 12.8mm laminated glass for enhanced safety and to ensure that the glass would withstand the appropriate design loads.
There are a number of different glass types and thicknesses that can be used when specifying glass partitions, to suit both the desired acoustic performance and the glass application.
Not sure which glass type would best suit your project? Speak to our technical experts.
In our next blog post we take a look at maximum heights and partition stiffness – two other very important factors to consider when specifying glass type and thickness.