LAMINATED GLASS KEY POINTS
- Laminated toughened glass offers additional safety benefits.
- Interlayers can be used for privacy, tinting, colouring, etc.
- PVB is most common due to its cost/performance balance.
What is laminated glass?
Two layers of toughened glass are joined with an interlayer providing the benefit of a second form of guarding preserved by the remaining panel until a full replacement can be made, enhancing both the safety of the balcony it is guarding and the balconies or areas below. Laminated glass is typically considered to offer the best panel security for glass balustrades.
It is important to note that what is typically referred to in the industry as “laminated glass”, is usually temper toughened glass which has also been laminated, not normally untoughened laminated glass.
Heat strengthened and laminated glass is less common for balustrades, but more common in glass floors (chosen for its larger fragmentation pattern if broken). Untoughened, or annealed glass which has been laminated together is rarely used for balconies, occasionally it will be used for special scenarios (e.g. where the glass forms a tight curved radius).
Why use laminated glass?
One of the main benefits of using laminated glass (as noted in BS 6180:2011), is that when monolithic glass breaks it will smash into small particles which are not contained, whereas the interlayer of laminated glass will hold the majority of particles in most typical breakages.
Another benefit of using toughened and laminated glass, is that BS6180:2011 8.5.2 states that a handrail should be used unless a laminated toughened glass is used. This allows a minimalistic aesthetic appearance to be achieved.
Types of interlayer
PVB (Poly Vinyl Butyral) is the most commonly used interlayer in glass balustrades. This is because it offers a good balance between being cost effective, offering a relatively good edge detail, performance and durability. PVB is available in a very extensive range of colours and designs enabling glass to be coloured, tinted, obscured or patterned very effectively.
CIP (Cast in Place) is not a laminated interlayer sheet, but rather a poured resin. Sapphire does not recommend the use of CIP panels because the edge finish typically looks messy and requires concealing the edges strips due to the tape used around the holes and edges to contain the resin.
SGP (SentryGlas Plus), a registered trade mark of DuPont could be specified for exposed or potentially ‘dangerous’ environments; an SGP interlayer may be up to 5 times stronger than a PVB interlayer. In our experience, it is typically a very costly option. It comes in sheets rather than rolls like PVB often meaning there is high waste for balustrade glass production.
EVA (Ethylene Vinyl Acetate) is not as common as PVB and is from our experience more expensive. It is typically used to encapsulate other components, such as LED lighting, into glass and offers the benefits of being less water absorbent.
Whichever interlayer is selected we recommend that an additional capping or handrail is also considered. Aesthetically, this helps to achieve panel alignment, both vertically with adjacent balustrade panels but also any slight misalignment of the two pieces which have been laminated to each other. It also reduces the risk of impact damage, and the risk of delamination along the top edge caused by water.