Impact vs Non-Impact Windows

Watch what happens when hurricane debris strikes. One shatters completely, the other holds together. This difference can mean life or death for your building's envelope.

Non-Impact Glass

Standard tempered/annealed glass
BREACH - ENVELOPE FAILED

Impact-Rated Glass

Laminated with PVB interlayer
PASS - ENVELOPE INTACT

Non-Impact Result

  • Glass shatters completely
  • Opening created for wind entry
  • Interior pressurizes rapidly
  • Roof lift-off risk increases
  • Water intrusion guaranteed

Impact-Rated Result

  • Glass cracks but stays intact
  • PVB interlayer holds shards
  • Building envelope maintained
  • Survives 9,000 pressure cycles
  • Water infiltration prevented

Glass Construction Comparison

The critical difference is in what's between the glass layers.

Tempered

Non-Impact Glass

Single or double pane tempered or annealed glass. Designed to break safely into small pieces but cannot resist penetration.

  • ConstructionSingle/Double Pane
  • InterlayerNone or Air Gap
  • Break PatternComplete Shatter
  • Debris RatingNone
  • HVHZ CompliantNo (Needs Shutters)
Glass
PVB
Glass

Impact-Rated Glass

Laminated glass with polyvinyl butyral (PVB) interlayer that bonds the glass layers together, preventing penetration even when cracked.

  • ConstructionLaminated Multi-Pane
  • Interlayer0.090" PVB Minimum
  • Break PatternCracks, Stays Intact
  • Debris RatingLarge Missile D
  • HVHZ CompliantYes

Frequently Asked Questions

Common questions about impact vs non-impact windows.

What's the difference between impact and non-impact windows?
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Impact windows use laminated glass with a plastic interlayer (PVB) that holds the glass together when broken. Non-impact windows use standard tempered or annealed glass that shatters completely, creating an opening for wind and water to enter your building.
Do I need impact windows in Palm Beach County?
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In HVHZ (High Velocity Hurricane Zone) areas of Palm Beach County, impact-rated products or approved shutters are required. In non-HVHZ areas, you can use non-impact windows with approved hurricane shutters for wind-borne debris protection.
How are impact windows tested?
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Impact windows undergo large missile testing (9-lb 2x4 lumber at 50 fps) and small missile testing (10 steel balls at 80 fps) per ASTM E1886/E1996. After impact, they must survive 9,000 pressure cycles without creating an opening in the building envelope.
Are impact windows more expensive than non-impact?
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Impact windows typically cost 50-100% more than comparable non-impact windows. However, they eliminate the need for separate hurricane shutters, provide year-round protection, and often reduce insurance premiums by 25-45%, offsetting much of the cost over time.
Can I use shutters instead of impact windows?
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Yes, in most areas approved hurricane shutters provide equivalent protection to impact windows. The window/shutter combination must meet the required design pressure and debris impact ratings. However, shutters require deployment before storms and don't provide everyday security benefits.

Calculate Your Impact Requirements

Get instant wind load calculations to determine if you need impact-rated products for your Palm Beach County project.

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