Why should toughened glass be used for domestic rooflights?

All glass installed overhead in products such as rooflights and skylights must be ‘safety glass’; by that we mean toughened or tempered glass. Toughened glass is designed to break into small fragments if it is broken rather than larger shards which are far more likely to cause injury, particularly if the glass is installed overhead. Toughened safety glass is 4-5 times stronger than standard annealed glass. In most domestic settings, glass rooflights will use toughened safety glass of at least 4mm, although some manufacturers prefer to use 6mm as it has less deflection. This reduces the potential for water ponding on the rooflight. Due to the manufacturing process, toughened glass can sometimes be susceptible to ‘spontaneous breakage’ because of Nickel Sulphide impurities present in the glass. Manufacturers can effectively combat this by using a process called ‘heat soak testing’ which greatly reduces the chances of spontaneous breakage. This process is usually used for walk on specification glass for obvious safety reasons. Rooflights with a pane size above 3m2 or between 5mts and 13mts from floor level are slightly different and require the use of laminated glass. This is designed to physically hold the glass together and prevent it from falling, even if the glass itself has been broken; this can be either annealed laminated or sometimes toughened laminated. All rooflights.com products are toughened heat soak tested as standard.

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