Ratings come first
Everything else follows from one question: what is this panel expected to stop?
Ballistic glazing is classified by calibre, projectile velocity, number of rounds and the spacing between impacts. A build rated for a handgun is thinner, lighter and cheaper than one rated for a rifle, and specifying above the real requirement adds weight and cost that the structure then has to carry.
So the specification conversation runs:
- What threat level does this opening need?
- Is the frame and its fixing rated to the same level?
- Does the panel need to open, and how is that hardware rated?
- What else must it do — thermal, acoustic, solar control?
Skipping the second question is the most common and most serious mistake.
How it stops a round
Layers of glass, polycarbonate or acrylic bonded with polymer interlayers. On impact the outer layer slows and deforms the projectile — spreading its point load over a wider area — and the inner layers absorb and disperse the remaining energy laterally.
The energy ends up distributed across the panel rather than concentrated at one point. What varies between builds is the number, thickness and material of those layers.
Spall: the thing people miss
When a ballistic panel is struck, fragments can be thrown off the protected face even if the round does not penetrate. That is spall, and it can injure someone standing behind the glass.
No-spall builds add a polycarbonate or film layer on the protected side to contain it. Whether you need that depends on how close occupants stand to the glass — a teller position needs it; a perimeter window generally does not.
The five constructions
Laminated glass. Multiple glass plies with PVB or polyurethane interlayers. The default: excellent optics, scratch-resistant, heavy.
Polycarbonate. Much lighter for the same rating, and inherently no-spall. Scratches easily and yellows with UV over time.
Glass-clad polycarbonate. A polycarbonate core with glass faces — the scratch resistance of glass with the weight and spall behaviour of polycarbonate.
Acrylic. Monolithic, lighter than glass, good clarity, generally lower ratings.
One-way glass. Ballistic protection combined with a mirrored or reflective face for observation from the protected side.
Insulated units. Any of the above built into a sealed unit, so security does not cost thermal comfort.
Where it belongs
Jewellery showrooms, banks and cash-handling counters, ground-floor retail with high-value stock, some corporate and government offices, and a small number of residences with a defined requirement.
For most homes, laminated security glass is the proportionate answer — see bulletproof windows in Mumbai for that comparison.