Tempered Glass Is Strong
So why does it still need safety film?
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Tempered glass is approximately four to five times stronger than ordinary annealed glass, making it one of the safest glazing materials used in modern buildings. Yet despite its impressive strength, it can still shatter instantly if its edge or corner is damaged. When that happens, an entire pane can disintegrate within a fraction of a second, scattering thousands of small glass fragments across the surrounding area.
Safety film does not prevent tempered glass from breaking. Instead, it performs a different but equally important function. Once the glass fails, the film holds the broken fragments together, reducing the risk of injury, helping to secure the opening, and minimising disruption until the damaged panel can be replaced.
This distinction explains why architects, facility managers, schools, hospitals, commercial buildings, and MCSTs throughout Singapore continue to specify safety and security window film even where tempered glass has already been installed.
Tempered Glass Alone Versus Tempered Glass With Safety Film
The table highlights an important point. Safety film does not significantly increase the structural strength of tempered glass before it breaks. Its primary purpose is to improve what happens after breakage by retaining the fractured glass on the pane.
How Strong Is Tempered Glass?
Tempered glass, also known as toughened glass, is produced by heating ordinary glass to approximately 620°C before rapidly cooling both surfaces with high-pressure air. This thermal tempering process permanently compresses the outer surfaces while placing the centre of the glass under tension.
The result is a glazing material that is typically four to five times stronger than ordinary annealed glass of the same thickness.
Under ASTM C1048, tempered glass generally achieves surface compression exceeding 10,000 psi and is capable of resisting bending and impact loads approaching 24,000 psi before failure. By comparison, ordinary annealed glass typically fractures at around 6,000 psi.
This exceptional strength makes tempered glass the standard choice for sliding doors, office partitions, shopfronts, shower screens, curtain walls, and many other architectural applications throughout Singapore.
The Hidden Weakness Behind Its Strength
The very process that gives tempered glass its strength also creates its greatest vulnerability.
Because the outer surfaces remain under permanent compression while the centre stays under tension, the glass stores a significant amount of internal energy. As long as the surface layer remains intact, this energy remains safely locked inside the pane.
However, if an edge or corner becomes chipped or damaged, that balance can collapse almost instantly. Unlike the centre of the glass, the edges contain exposed stress concentrations where even a relatively small impact can trigger complete failure.
Instead of cracking gradually like ordinary glass, tempered glass releases its stored energy almost immediately, causing the entire pane to break into thousands of small fragments.
Besides accidental impact, tempered glass may also fail due to nickel sulphide inclusions, previous edge damage, installation stresses, or thermal stress. Although spontaneous breakage is uncommon, it is a recognised characteristic of tempered glass and one reason many building owners choose to add an additional layer of protection.
This is also why Window-Cool’s BCA-registered and BizSAFE Level 4 certified installation teams handle tempered glass with exceptional care during transport and installation. Improper handling at the edges remains one of the leading causes of unexpected glass failure.
When Singapore Regulations Require Laminated Glass Instead of Safety Film
Singapore’s Building Control Regulations distinguish between laminated glass and retrofit safety film.
Since 1 July 2011, where glass forms part or the whole of a safety barrier under Clause H of the Fifth Schedule to the Building Control Regulations, the glazing must be laminated and comply with Singapore Standard SS341:2001.
The requirement is based on the function of the glazing rather than a fixed installation height. If the glass is acting as a protective barrier against falls, such as a balcony balustrade, stair guard, or guarding system, laminated glass is required.
For overhead glazing such as canopies and glass roofs installed 2.4 metres or more above the floor, the glazing must also comply with SS341:2001. Where tempered glass is used, the design must include secondary protection to reduce the risk of injury should spontaneous breakage occur.
Safety film should therefore be viewed as a retrofit enhancement rather than a replacement for laminated glass where Singapore regulations specifically require laminated glazing.
Building owners should always verify the intended function of their glazing with an architect, Qualified Person (QP), or BCA-registered contractor before specifying safety film in place of laminated glass.
Why Safety Film Cannot Replace Laminated Glass
Although both laminated glass and safety film improve post-breakage safety, they achieve this in fundamentally different ways.
Laminated glass is manufactured by permanently bonding two or more sheets of glass together with a structural interlayer during production. After breakage, the interlayer continues supporting the broken glass as an integrated glazing system designed to satisfy structural safety requirements.
Safety film, by contrast, is applied to the surface of existing glass as a retrofit. While high-quality safety film significantly improves fragment retention and reduces injury, it does not transform tempered glass into laminated glass under SS341:2001 where laminated glazing is specifically required by Singapore regulations.
The two systems complement each other, but they are not interchangeable.
Why Window-Cool Recommends Safety Film
Selecting the correct glazing solution begins with understanding the purpose of the glass rather than applying the same product everywhere. Where Singapore regulations require laminated glass for safety barriers, laminated glass remains the correct specification.
For existing tempered glass that is not performing a barrier function, professionally installed safety and security film provides an effective retrofit that improves post-breakage safety, enhances security, and helps reduce operational disruption without replacing the existing glazing.
Window-Cool installs LLumar safety and security films that have been independently tested to internationally recognised standards, including:
• Safety Glazing: ANSI Z97.1, CPSC 16 CFR 1201 and EN12600.
• Blast Mitigation: GSA TS01, ISO 16933, ASTM F1642 and ASTM F2912, including successful Intertek airblast testing on LLumar 8 mil systems.
• Manual Attack Resistance: EN356 Level P2A.
• Impact and Wind Resistance: ASTM E1886 and ASTM E1996 Level C.
Every installation is carried out by BCA-registered and BizSAFE Level 4 certified teams operating under our ISO 9001 quality management system, ensuring consistent workmanship for residential, commercial and institutional projects throughout Singapore.
Frequently Asked Questions
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No. Tempered glass is approximately four to five times stronger than ordinary glass, but it can still shatter if its edges or corners are damaged or subjected to concentrated impact.
Not significantly. Safety film is designed primarily to retain broken glass fragments after breakage rather than substantially increasing the structural strength of the glass beforehand.
No. Safety film cannot prevent tempered glass from breaking or spontaneously shattering. Its purpose is to hold the broken fragments together after failure, reducing injury and helping maintain the integrity of the opening until replacement glass is installed.
No. Where glass performs a safety barrier function under Clause H of the Fifth Schedule to the Building Control Regulations, Singapore requires laminated glass compliant with SS341:2001. Safety film cannot be substituted for this requirement.
Safety film remains an excellent retrofit solution for existing tempered glass used in standard windows, partitions, shopfronts, office glazing, and many other non-barrier applications.
Yes. Although uncommon, tempered glass can occasionally shatter spontaneously due to nickel sulphide inclusions, hidden edge damage, thermal stress, or stresses introduced during manufacture or installation.
Building regulations do not require safety film for every tempered glass installation. However, many building owners, MCSTs, schools, hospitals, and commercial facilities choose to install it because it improves post-breakage safety, reduces flying glass hazards, enhances security, and helps minimise downtime after unexpected glass failure.
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