When a building cannot replace its windows but needs them hardened, the answer is a security window retrofit: a polycarbonate overglaze shield mounted over the existing glass. It is faster and cheaper than a full replacement, and it upgrades the opening without gutting the facade.
How a retrofit overglaze works
A ballistic or forced-entry polycarbonate panel is fabricated to the existing opening, sized and edged to the frame, and anchored through a continuous restraint so the impact load spreads rather than concentrating at a bolt. Because polycarbonate is far lighter than glass of equal protection, the existing frame often carries it without reinforcement, and the panel keeps the window clear.
Retrofit steps that protect the opening
- Measure the opening and confirm the frame detail.
- Set the threat level (forced entry or a UL 752 ballistic level).
- Size and edge the polycarbonate shield to the frame.
- Anchor through continuous restraint, not point bolts.
- Confirm the panel stays clear for daylight and sightlines.
For the ballistic version of this upgrade, see bullet resistant window, and for the composite build, glass clad polycarbonate glazing.
Frequently Asked Questions
Q: Can a security window retrofit use the existing frame?
A:Often yes, because polycarbonate is lighter than laminated glass at equal protection; confirm the frame carries the panel and the fixing transfers load evenly.
Q: Will the retrofit block the light?
A:No, a polycarbonate overglaze keeps good transparency, so the window retains daylight and sightlines while gaining the protection.
For a project-specific quotation on bullet resistant polycarbonate or security glazing, email oversales@rpplexiglass.com with your threat level, panel size and frame detail.