Tempered glass: strong, then gone
Tempered glass is heat-treated to be about four times stronger than regular glass. When it does break, it shatters into small, relatively harmless pebbles instead of sharp shards. That's why it's used in shower doors and car side windows — safe breakage matters there.
But here's the catch for storms: once tempered glass breaks, the opening is open. The glass is gone. Wind and rain pour in. That's fine for a shower door. It's terrible for a hurricane.
Laminated glass: strong, then still there
Laminated glass is two (or more) layers of glass bonded to a tough plastic inner layer — usually PVB (polyvinyl butyral). When something hits it, the glass can crack, but the inner layer holds all the pieces together. The window looks like a cracked windshield: damaged, but still sealed.
This is why impact windows use laminated glass. The whole point is that the opening stays closed even after a hit — because a sealed opening is what keeps wind from getting inside and lifting the roof.
What this means for your home
Storm protection comes from the laminated inner layer staying intact. Noise reduction comes from it too — the plastic layer dampens sound vibrations, which is why impact windows are noticeably quieter. UV filtering is another bonus: the inner layer blocks most UV, so floors and furniture fade slower.
A common mix-up
Some people hear "impact glass" and think of tempered glass because both are "stronger glass." They're different products for different jobs. If a quote doesn't say laminated, ask — tempered alone is not impact-rated for hurricanes.