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UV radiation – is your fire safety glass durable enough?

One of the main appeals of modern fire safety glass solutions is the successful balancing act between fire protection and aesthetics. However, with continuous exposure to UV radiation, the appearance of some fire safety glass systems can be compromised in as little as a few years. Here, Richard Ainsworth, Group Technical Director at Pyroguard, explores how this can be avoided…

Vivanta New Delhi Dwarka

Glass continues to be a popular building material by architects and specifiers, a trend that is surely set to remain. Thanks to market developments, innovations and technological advancements over the last three decades or so, the fire safety glass industry has advanced significantly. Today, not only does it provide a vast range of aesthetically pleasing high-performance fire safety glazing solutions, but also offers many additional performance properties such as acoustics, thermal and a much improved light transmission. Specified and installed correctly, these solutions have enabled the creation of contemporary buildings and spaces – whether used internally to create light, open and airy spaces, installed in an atrium to create a central focal feature, or used externally within façade and curtain wall systems, providing a functional yet striking contemporary sight on our urban skylines.

But how can you ensure that your fire safety glass remains looking crystal clear for longer? Laminated fire safety glass systems can be manufactured from various panes of toughened glass, with a specially engineered fire-resistant interlayer in between. Installed on the exterior face of a building, or indeed anywhere where the glass is exposed to UV radiation, this exposure can have a marked effect on the appearance of some fire safety glasses. While the glass itself and the system’s performance in the event of a fire is thankfully usually unaffected, depending on its chemical composition, the fire-resistant interlayer between the individual glass panes can react to the natural UV light exposure. In countries where higher temperatures are experienced, this reaction can be accelerated even further.

UV degradation can take numerous forms, such as the formation of micro-bubbles in the interlayer, delamination, yellowing or cloudiness of the glass – leading to a decreased level of light transmittance or unexpected and unsightly change of appearance.

Understandably, when glass is chosen for its striking and contemporary visual appearance, the last thing you want is for this to be compromised just a few years after its installation. So, the all-important question is: how can you ensure fire safety glass will maintain its aesthetic performance for years to come, resisting the effects of daily exposure to UV radiation?

What do the Building Regulations say?

Looking at the Regulations, fire glass products should be tested to the relevant International Standards for durability: in Europe, the standard UV durability test is detailed in EN ISO 12543-4 and provides a means of accelerated testing. Here, laminated glass samples are placed into a test rig within a controlled laboratory environment and subjected to standardised levels of heat and UV light. More specifically, this test is usually formed of a wall of UV lightbulbs emitting 900W/m2 for 2,000 hours while the chamber is maintained at 45oC. Unfortunately, it is complex to map the results of this test to a real-world product lifetime and the standard is more lenient when defining a ‘pass’ for fire rated glass – allowing some defects including (surprisingly) bubbles and cloudiness.  This, in some cases, can render the claim of a ‘pass’ close to meaningless.

Real-world weathering

Real-world weathering testing is another way in which specifiers, installers and fabricators can gain a greater understanding into the expected long-term performance of a fire safety glass. As the name suggests, real-world weathering involves samples being placed on testing sites around the world, exposing them to the radiant energy presented in sunlight, as well as heat and water (predominantly in the form of humidity, dew and rain). Unsurprisingly, Florida and Arizona are popular locations for outdoor weathering tests, due to their climate’s high-intensity sunlight and reliably elevated temperatures all year round. A disadvantage of this approach is the long length of time required to approve new products.

Exceeding expectations

Installers and fabricators might be wise to seek out products and solutions that haven’t merely met the required test standards but have also exceeded them, providing complete assurance that the glass will continue to look visually appealing and transparent for longer. For example, panes of Pyroguard Protect, taken from Pyroguard’s range of gel-filled toughened fire safety glass, have recently undergone a series of new accelerated UV durability tests with some fantastic results. Samples were found to be unaffected by the UV radiation specified in EN ISO 12543-4 even after 10,000 hours of testing – that’s 8,000 hours longer, or five times longer, than the standard 2,000 hours test specified by the standard. Moreover, no defects were detected.

When it comes to choosing fire safety glass and combining fire performance with architectural design, there are numerous factors to consider to ensure that the optimum solution is chosen. With the added concern of weathering and continuous UV exposure potentially detrimentally impacting the aesthetics of a building’s fire safety glass, it’s important to check manufacturer’s warranties for exclusions relating to durability issues and look at the test certification available. Careful product choice can help construct safe and attractive buildings that are sure to stand the test of time.

For more information about Pyroguard Protect please contact us.

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