Replacing a window is expensive and disruptive, which is why an overglaze polycarbonate shield is often the smarter upgrade: a transparent polycarbonate panel fitted over the existing glass that adds impact and forced-entry resistance without pulling out the original window.
The retrofit that keeps the window
An overglaze shield sits in front of the existing glazing, converting a weak window into one that resists forced entry and impact. The frame detail matters most: the shield has to be fixed to the structural frame, not to the old glass, with the holding force matched to the threat. Because the panel is transparent, the original window keeps working, and the upgrade is reversible — which makes it practical for rented or heritage buildings where replacing the window is not an option.
Retrofit checklist for an overglaze shield
- Fix the shield to the structural frame, not to the old glass.
- Match the holding force to the threat level.
- Keep the panel transparent so the original window stays usable.
- Use an overglaze build where replacing the window is impractical.
How a full window is rebuilt for security is covered in the security window retrofit guide, and the bank-level glazing in bulletproof window for banks.
Frequently Asked Questions
Q: What is an overglaze polycarbonate shield?
A:It is a transparent polycarbonate panel fitted over existing glazing to add impact and forced-entry resistance, without replacing the original window.
Q: Does an overglaze shield weaken the existing window?
A:No. Fixed to the structural frame, it strengthens the opening and keeps the original window usable. The frame holding force and threat match decide the real security gain.
For a bullet-resistant or security polycarbonate glazing quoted to your threat level, panel size and frame system, email oversales@rpplexiglass.com with the threat level, panel dimensions and the opening type you need to protect.