School of Specification – Security through laminated glass

Allan Gibson, AIS Global Product/Marketing Segment Manager at Kuraray Europe, has produced a School of Specification module exploring security using laminated glass. Here, he considers the main security threats for glazing and what can be done to mitigate them.

Photo: mike_shots/shutterstock 2018

What are the main security threats for glazing and what standards/classifications apply to them?
Advances in façade design now allow for larger laminated glass panels with minimal framing, but this increases exposure to man-made threats in three key areas:

Blast resistance. Explosions create pressure waves that can shatter glazing, causing injury from glass fragments. This is classified under EN 16933 (arena testing) or EN 13541 (shock tube testing).
Ballistic resistance: Firearm attacks risk bullet penetration, leading to injury or unauthorised access. EN 1063 classifies resistance from BR1 to BR7. Spall protection (NS classification) can be added with Spallshield films.
Forced entry resistance:Burglary, riots, or vandalism may involve tools or blunt force to breach glazing. This is classified under EN 356(P1A–P8B), LPS 1270 (1A–8G), and PAS 24.

Security must be considered early in design, following overlays such as the RIBA stages developed with NPSA and Secured by Design.

What is laminated glass and how does it differ from other types of safety glass?
Laminated glass is made by bonding two or more layers of glass with a specialist interlayer, such as SentryGlas®, to enhance strength and security. The interlayer improves the mechanical properties and coupling effect, preventing penetration or failure under load. Unlike other types of safety glass, such as tempered glass, which shatters into small pieces on impact, laminated glass holds together after breakage, maintaining a protective barrier. Its performance also depends on proper framing and secure anchoring to the substrate.

Security must be considered early in design, following overlays such as the RIBA stages developed with NPSA and Secured by Design”

What are the different types of interlayer commonly used in laminated glass and how do they work?
Several types of interlayers are used in laminated safety glass depending on the threat level and performance requirements:

PVB (polyvinyl butyral). Common for general safety and security glazing. It can offer some blast mitigation at lower threat levels due to its elastic properties.
Ionoplast interlayer, such as SentryGlas®. Provides higher strength and stiffness than PVB, allowing for thinner glass constructions while maintaining high security. It is often used in ballistic- and forced-entry-resistant glazing.
Specialty interlayers, such as Spallshield. Applied in ballistic applications to reduce or prevent glass spall, protecting occupants from secondary fragmentation.

For higher threat scenarios, such as ballistic or forced-entry resistance, a multi-layered construction combining different interlayers and glass types is typically required to meet certification standards.

In what ways can laminated glass be used to mitigate the security threats posed by blast, ballistics, and forced entry?
Laminated glass mitigates these threats through tailored glass and interlayer combinations based on the threat level:

Blast mitigation. Typically two or more glass layers laminated with PVB or SentryGlas®, depending on blast severity. PVB can address lower-level blasts, while SentryGlas® provides enhanced stiffness and post-breakage performance under higher blast loads.
Ballistic resistance. Typically multi-layered glazing with combinations of glass, SentryGlas®, and PVB or spall shield films. Thicker glass composites prevent projectile penetration and control spall.
Forced entry resistance. Typically multiple laminated glass layers with PVB or SentryGlas®. Builds vary from simple PVB-laminated glass for lower risks to SentryGlas® reinforced laminates for extended attack resistance.

Laminated glass systems provide a ‘transparent armour’ when designed with the appropriate glass thicknesses, interlayer types, and secure fixing methods, allowing architects to meet both security and aesthetic goals.