Glass – Strength and Size Matters

Glazing is a highly versatile option for the exterior of many buildings. Susan Sinden, Commercial Manager of ESG Group, looks at how specifying strong, durable toughened laminated glass allows architects to create uninterrupted clear views, using larger panel sizes.

Lamination, which brings both strength and added safety to an already desirable toughened glass building product, has allowed architects to push the boundaries of design in the building envelope.

In the process of lamination, two layers of glass are sandwiched together using a PVB (PolyVinyl Butyrall) interlayer, which bonds the layers of glass together. This technique is normally used to combine two sheets of toughened glass, adding strength, safety, and a wide range of functionality.

Critically, lamination has allowed us to increase the size of the glass panel. With the considerable additional strength which lamination brings, we can now produce glass panels of several metres in height and width, and these panels can be joined unobtrusively, to produce large expanses of glass which to be appear uninterrupted, allowing architects full reign for their imagination, as well as the freedom to create some of our most iconic modern buildings.

Lamination brings a host of other benefits too. By laminating two layers of toughened glass, security is greatly enhanced. If a panel of toughened laminated glass is damaged, the broken glass will usually stay in place. Most of the glass fragments are held in place by the interlayer to which they are bonded, so, although the appearance of the glass may be marred, and the panel may become bowed or misshapen, it may not even need to be boarded over until a replacement can be installed. This not only protects the building’s users from coming into contact with shards of glass, it also helps to preserve the integrity of the external envelope, which would inevitably be compromised with non-laminated glass.

Security can be enhanced still further, by laminating specially processed security glass with specialised interlayers which, when used together, form a high security glass which will withstand multiple blows from heavy objects or weapons. High security glass either prevents the external envelope from being breached altogether or significantly extends the time that it would take to breach the glass panel, sufficiently to deter the would-be intruder. Laminated security glass can pass the standards for EN356 manual attack resistant glass. And even ballistic resistance can be added with the use of the appropriate advanced interlayer. Again, larger panels also allow uninterrupted sight lines, which can be critical in high security areas such as airports and other transport termini.

High security laminated glass products are now commonly used in applications such as high value goods shop fronts, and also inside retail outlets in display and jewellery counters. They are also increasingly used to protect bank tellers or public service employees in locations such as benefits offices.

We can also use interlayers to introduce some other properties such as sound attenuation. This can benefit those outside the building, by muffling the noise of heavy machinery from a manufacturing process, but it can also help to provide a more tranquil indoor environment for the building’s occupiers, whether in an office or a domestic setting.

It doesn’t have to be either or; we can use interlayers to create sound attenuation with high security or to introduce a few other features such as privacy. Seclusion can be either permanent or temporary.

One of the most popular advances in interlayer technology in the past decade has been the rise in use of the switchable interlayer. A switchable privacy layer allows the glass panel to be either transparent or opaque at will, allowing occupants to admire the view if they wish, but also to enjoy privacy. The interlayer is controlled by a small electric current. When current is passed through the interlayer, particles inside it line up to allow light to pass through and the panel becomes see-through. However, when the current is switched off, the particles in the interlayer align randomly, so that light can no longer pass through, making it opaque. The glass panel can be clear or opaque, quite literally at the touch of a button, or a remote control.

Glass processing technology has advanced almost beyond recognition. Where windows were, historically, necessarily small, both for cost considerations and to make them less likely to break; we can now provide vast expanses of glazing, which are cost effective, extremely long lasting and highly secure.

Glass, one of the oldest building materials on the planet, is still at the forefront of iconic new architecture. Strength and size definitely do matter.

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