Tempered glass is actually designed to minimize injury rather than prevent entry. It shatters into tens of thousands of pieces when hit. Tempered glass keeps people safer from injury or being cut by glass—such as in a car accident—but doesn’t stop intruders from breaking the glass and getting in. In fact, a sharp-edged object will break the glass’ ”surface tension” and shatter tempered glass without any impact and with very little noise.
Laminated glass is much harder for would-be burglars to penetrate. A laminated glass system usually consists of one composite pane made up of a polyvinyl butyral (PVB) interlayer sandwiched by two sheets of glass—and then another pane of standard glass. That special PVB interlayer is what keeps the glass from being penetrated. There are different thicknesses of PVB interlayers. Thicker interlayers (such as .060 or .090) will provide much more protection than thinner interlayers (.030 size, for example). In tests, windows and doors with thicker interlayers have withstood more than 30 blows from a baseball bat before a hole the size of a quarter appears. The glass will shatter – but the PVB won’t break, so no one can get through.
Tempered glass is a good choice in some situations—such as patio doors, or very large windows with big expanses of glass—because it’s safe when broken (often a concern of homeowners with kids). But for home security, to help prevent intrusions, laminated glass is more effective.