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Interior and Exterior Bulletproof Windows: What’s the Difference?

May 24, 2024

When considering the security of bulletproof windows for your facility, it might be tempting to choose the most affordable option. However, opting for the wrong type of ballistic glass can lead to significant problems, including compromised safety and durability.

Not all bulletproof glass is suitable for exterior use. Using the wrong type outdoors can result in unsightly visual effects such as yellowing or even damage that compromises the glass's bullet-resistance.

This article will explain the differences between interior and exterior bulletproof windows. For specific questions, you can visit our detailed guide here.

Interior and Exterior Bulletproof Windows: What’s the Difference?

Key Differences Between Interior and Exterior Bulletproof Windows

The primary difference between interior and exterior bulletproof windows is their ability to withstand environmental elements. Glass-clad polycarbonate (GCP) and insulated glazing have protective glass caps that shield against natural forces. Conversely, acrylic and polycarbonate do not, making them suitable only for interior use. While GCP and insulated glazing can be used indoors or outdoors, insulated glass is typically preferred for exterior applications due to its air gap that enhances protection against the elements.

Beyond weather resistance, there are several other distinctions between interior and exterior bulletproof glass:

  • Thermal Properties:
    Exterior glass often needs better thermal insulation to handle temperature variations.
  • Thickness:
    Different applications may require varying thicknesses for optimal performance.
  • Light Transmission:
    The amount of light passing through can vary, affecting clarity.
  • Bullet-Resistance Rating:
    Levels of ballistic protection differ, with some glass designed to withstand higher impacts.
  • Cost:
    Exterior bulletproof glass tends to be more expensive due to the additional materials and manufacturing processes involved.

These differences do not imply that one type is superior to another; rather, the right choice depends on your specific needs.

Types of Bulletproof Glass for Windows

Interior Bulletproof Windows

Acrylic and Polycarbonate Glazing:

  • Acrylic:
    Cost-effective, high light transmission, resistant to yellowing, available in UL 752 Levels 1 and 2.
  • Polycarbonate:
    Slightly lower light transmission, may yellow over time with UV exposure, available in UL Levels 1, 2, and 3, also offers forced entry protection.

Exterior Bulletproof Windows

Glass-Clad Polycarbonate (GCP) and Insulated Glass:

  • Glass-Clad Polycarbonate (GCP):
    High-performance, customizable, can be manufactured to UL Levels 1-8, resistant to blasts, forced entry, and harsh weather conditions. Custom options include tints and one-way mirrors.
  • Insulated Glass:
    High protection rating, efficient thermal insulation, available in UL Levels 1-5, offering up to 90% light transmission for excellent clarity.

Retrofitting Bulletproof Exterior Windows Using Backglazing

Adding bulletproof windows to existing structures can be challenging, especially for historic buildings or modern designs with unique features. Backglazing provides a solution by installing a ballistic glass layer behind the existing non-rated glass. This method maintains the building's aesthetic while enhancing security without visibility or compliance issues. Since it is not exposed to the elements, backglazing can use acrylic or polycarbonate, offering additional benefits typically unavailable for exterior windows.


Selecting the right bulletproof windows for your facility can be overwhelming given the variety of options. The decision should be based on the specific requirements and conditions of your site. For expert guidance and a custom solution tailored to your needs, visit our comprehensive guide on bulletproof windows here.

@TSSBulletProof #TSSBulletProof #bulletproof #healthcaresecurity #security #bulletproofglass

Company: Total Security Solutions Inc

Product: Ballistic Security Glass




Bullet Resistant