By Mike Wood, Pilkington UK Ltd
One of the most significant themes in today’s building designs is the extensive use of glass, not only by area but also in the range of glass function. The story of architecture is inextricably linked to glass technology from Scheerbart’s vision in 1914 of the all-glass building through the flowering of the international school led by van der Rohe to the advances from the 1970s of the high tech style.
Not only has this been a question of larger glass panes with higher quality and lower cost due to the efficient high output capability of the Pilkington, now global, float process. There have been tremendous developments in coatings, leading to sophisticated light and energy selective coatings which provide the most subtle of tints with high performance solar gain and energy efficiency. Such innovations have allowed the creation of inspirational buildings, making the most of glass adaptability to maximise functionality and natural lighting without losing interior comfort, while exploiting the distinctive eye-catching aesthetics that only the durable crystal qualities of glass provide.
Developments towards the substantially all-glass building would not have been possible without advances in fire-resistant glass. All structures require built-in protection to limit fire movement, prevent collapse and safeguard occupants against the effects of fire. A number of fire-resistant glazing technologies are now available. Products fall into two distinct classes: either integrity (i.e. a physical barrier against fire and flames) or insulation (i.e. providing a physical and heat barrier against fire, determined in standard tests by measurements of surface temperatures on the non-fire side, which must be less than a rise of 140ºC over a standard test period, e.g. 30, 60, 90 or 120 minutes). Designers should not limit their aspirations for fear of being unable to provide effective transparent barriers against fire.
Common applications of fire-resistant glass include vision panels in fire doors as well as full-size glass doors (even including sliding door elements), transparent floor-to-ceiling walls, ceiling, floor and roof constructions, corridor partitions and atria glazing. Fire-resistant glass facades can also be used to protect against fire movement by break-out through glazed panels. Latest developments even include tremendously resilient blast-resistant constructions combined with fire-resistance.
The intumescent interlayer insu-lation with integrity glass types (e.g. Pilkington Pyrostop) also provide inherently good sound damping, which can be further increased with special acoustic formulations. That, in combination with extraordinarily good insulation against the heat of a fire, has allowed the development of integrally loaded fire-resistant glass floors, now well established and tested for use as whole areas or as inserted floor panels.
Developments in fire–resistant glass have not only included special technologies and continual refinements to expand scope of application. Standard glass is a material that is inherently weak in fire and prone to early failure and so special steps have to be taken to make glass sufficiently resistant against fire. The reliability and dependability of the fire-resistant glass technology must be robust: whenever a product is tested a successful result should be expected with a high degree of confidence every time. Consistent, reliable performance is essential in case of fire.
But that is not so with some types of fire-resistant glass. Modified toughened glass types in particular have fallen under a shadow because they can be sensitive to uneven thermal stress. They can fail, unpredictably, well before the allotted end of standard tests, with complete collapse of the glass panes. That weakness is well known in specialist glass and testing circles.
A new toughened glass
The weakness of modified toughened glass in fire has been recognised, at the same time registering the expressed need of designers and engineers for a functional basic integrity glass for the early stages of fire. Several R&D years have been spent in perfecting new types of modified toughened fire-resistant glass, which effectively sets a new performance benchmark for this type.