Safer - Secondary Glazing

Secondary glazing is a fully independent internal window, fitted on the room side of the existing primary window. This provides significant noise reduction, improved thermal performance and enhanced security.

It seems that nearly every day we hear stories of break-in’s and armed robberies. It is unnerving and affects all of us as we could all be at risk.

Secondary glazing can provide an unseen level of security to any property. It creates a second barrier of protection from the inside that can prevent the most determined thief or intruder. 

You may be looking to find ways to secure the contents of your building; be it physical high value objects or highly sensitive data or the people within. If this is the case, secondary glazing could provide the solution.


  • Deters intruders
  • Blast mitigation
  • Protection against firearms
  • Preserves clean environments
  • Second barrier to entry
  • Removes the need for unsightly grilles and bars
  • Maintains a normaised environment
  • Provides a delay mechanism

How it works

Physical attack

Under physical attack secondary glazing works by providing a second barrier to entry. At lower risk levels it must prevent manipulation of the locks and catches or removal of the glass or glazed panels. As the performance increases it must resist levering or use of cutting tools including penetration of the glazing, which at higher risk levels will be a sophisticated combination of glass, resin and polycarbonate. It is also worth noting that the attacker will have to break through the primary window first then work through the breached opening to attack the secondary glazing, by which time any vibration alarms will have been activated.

Blast mitigation

Secondary glazing can protect occupants and contents from the effects of an explosion by containing the flying shards of glass from the breakup of the primary window under the blast load. Fixings, frame, locks and glass are all designed to work in harmony deflecting and yielding to absorb the blast wave. PVB interlayers are used in the laminated glass composition to stretch and contain the blast.


Protection from firearm attack is achieved by several layers of glass of various thicknesses laminated together. The front layers of glass are designed to shatter, thereby absorbing the initial impact energy, subsequent glass and interlayers absorb the lower level shock waves. Lighter, thinner bullet resistant glass can be produced by the use of polycarbonate in the lamination. However, bullet resistant glass is not enough on its own as the same performance is required from all the components of the frame including any joints and junctions.


Fire resistant glazing provides a protected escape route for occupants. Specialist glass, together with fire and intumescent seals set within appropriate framing, resists the intense heat of a fire. This provides "integrity" which prevents breach of flames and gases, and where required "insulation" to reduce the transfer of heat.

Clean environments

Secondary glazing with its high-performance seals and easy clean surfaces can provide an efficiently sealed envelope in Clean, Antibacterial and Positive or Negative pressured environments. Fitted on the inside of primary windows or in partitions, it can be used to stop the ingress of dust and grime and provide a protected space for blinds

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