Laminated or Tempered Glass for Window Replacement in San Bernardino Earthquake Country

By Window Replacement San Bernardino Civil War Web · October 24, 2026

Laminated glass is the better choice when the goal is a window that stays closed after it breaks in an earthquake, and tempered glass is the better choice when heat resistance matters most. For many San Bernardino homes the strongest answer is a dual pane unit that uses both. The reasoning comes down to what each type does in the seconds after it fails.

What Happens When Each Glass Breaks

Tempered glass is ordinary glass that has been heated and cooled rapidly. That process makes it several times stronger than standard annealed glass of the same thickness, and it changes how the pane fails. When tempered glass breaks, the whole pane lets go at once and falls apart into small, blunt cubes. The opening is then completely empty.

Laminated glass is two or more lites bonded to a plastic interlayer, usually PVB. When it breaks, it cracks in a spiderweb pattern, but the fragments stay stuck to the interlayer and the pane generally stays in the frame. The window looks ruined, yet it still works as a barrier.

Neither one is unbreakable. Tempered glass is not shatterproof, and laminated glass is not earthquake proof. The difference is the aftermath: tempered drops granules and leaves a hole, while laminated stays put as a cracked but closed barrier.

Why Glass Breaks in a Quake

Glass in a house rarely breaks because something hits it. During shaking, the wall and window frame rack out of square, and the frame squeezes the glass. Once the stress passes what the pane can take, it cracks.

That is why San Bernardino homeowners should think about the second half of the event. Falling granules and chunks of tempered glass can still cut and injure anyone standing nearby, and an empty opening lets in wind, dust and weather. A cracked laminated pane keeps most of that out.

Why San Bernardino Raises the Stakes

The San Andreas Fault runs along the base of the San Bernardino Mountains on the north side of the city. Homes in the northern foothill areas, such as those near California State University, San Bernardino and in Verdemont, sit close to the fault trace. For those homes, keeping glass from falling inward or outward deserves extra weight in the decision.

Wind adds another reason. Santa Ana winds funnel through the Cajon Pass and hit the city hard, throwing branches and debris at windows. A broken laminated pane usually keeps wind, dust and embers out. A broken tempered pane leaves an open hole until it is boarded.

Start by Checking What You Already Have

Many older San Bernardino homes still have original single pane annealed glass, often in aluminum sliders. Annealed glass breaks into long, sharp shards and is the most dangerous glass to have during shaking. Replacing it comes first, before any debate about tempered versus laminated.

You can identify what is in a window without tools:

• Tempered glass normally carries a permanent etched mark, often called a bug, in one corner.
• Laminated glass shows a thin plastic line when you look at the edge of the pane.
• Glass with no mark and no visible interlayer should be treated as annealed until proven otherwise.

Do not assume a dual pane window is safety glass automatically. A dual pane unit can be made of two annealed lites.

Where Safety Glass Matters Most

Put safety glass first in the hazardous spots: doors, sidelites, tub and shower enclosures, large panes that sit low near the floor, and glass near stairs. Requirements vary by location in the house, so ask the installer what applies to each opening instead of guessing.

The Case for Laminated Glass

Beyond holding together in a quake, laminated glass has several practical advantages in this area.

• Break-in resistance. Laminated glass is significantly harder to break through, which deters smash and grab entry. Tempered glass is strong in the center of the pane, but a sharp blow near the edge can shatter it instantly. Laminated glass is not bulletproof and is not automatically impact rated.
• Noise reduction. It reduces noise better than a single monolithic lite of similar thickness, which helps for homes near the freeway corridors or the rail lines that run through the city and up the Cajon Pass.
• UV protection. The standard PVB interlayer blocks most UV light, which slows fading of floors and furniture behind sunny south and west facing windows in the Inland Empire heat.

The Case for Tempered Glass

Tempered glass earns its place in wildfire exposed foothill neighborhoods like Verdemont. It resists heat-induced cracking much better than annealed glass, and dual pane units with at least one tempered lite are a standard recommendation near the wildland edge.

The caution runs the other way for laminated glass in that setting. The interlayer can soften under intense heat, so ask the installer how a laminated lite would perform in that specific assembly before committing.

The Combination Many Homes Use

Insulated windows do not have to use one glass type throughout. A common upgrade is a dual pane unit with a tempered outer lite and a laminated inner lite. The outside gets strength and heat resistance, and the inside gets fragment retention, so broken glass is held on the room side rather than dropping toward the people in it.

Ask the installer to put the exact makeup of each lite in writing, including which one is on the interior.

Installation Details That Decide the Outcome

The glass type is only half the story. How the glass sits in the frame matters just as much.

• Glazing bite and clearance. Ask about setting blocks, edge clearance and adequate glazing bite. Glass with no room to move cracks sooner when the frame racks, and laminated glass with too little bite can pull out of the frame as a sheet.
• Weight. Laminated glass is heavier. Have the installer confirm that sash balances, hinges and rollers on operable windows and sliders are rated for the added weight, or the hardware will wear early.
• Edge sealing. Laminated edges must stay sealed. Long exposure to water, or contact with incompatible sealants, can cause cloudy delamination that starts at the edges. Ask that the installer use sealants rated compatible with the interlayer.
• Exact sizing. Tempered glass cannot be cut, drilled or edged after tempering. Every pane has to be ordered to exact size, so a measuring error means reordering, not trimming.

Bedroom Escape Windows

Windows meant for emergency escape need a sash that opens easily. Do not plan on breaking glass to get out. Because laminated glass is hard to break through and holds together when cracked, keep this in mind before putting laminated glass in an escape window, and confirm that the operating hardware still works smoothly with the heavier lite.

Care and Quirks of Each Type

Tempered glass can rarely break on its own with no impact, usually from a tiny inclusion in the glass or an old edge chip. If you find a chipped edge on a tempered pane, especially on a slider, plan to replace it.

Do not scrape tempered glass with a razor blade. Fine debris from the tempering process can drag across the surface and leave permanent scratches. Use non-abrasive cleaners and soft pads.

After a Noticeable Quake

Walk the house and check each pane. Look for:

• Cracks, including hairline ones in the corners
• Chipped edges
• Fogging between the panes of dual pane units, a sign the seal failed
• Sashes that now bind or will not lock

A cracked laminated pane still holds, but it needs replacement because it no longer has its full strength.

If Replacement Has to Wait

For existing annealed windows that cannot be replaced yet, professionally applied safety film is a stopgap. It holds shards together, and it works best when the film is anchored to the frame. It is not equivalent to factory laminated glass, and it should be treated as a temporary measure rather than a finished fix.

A Practical Way to Decide

Work through the choice in this order:

1. Replace any annealed glass in doors, low panes, bathrooms and stair areas first.
2. For homes close to the fault trace in the northern foothills, lean toward laminated glass on at least the interior lite.
3. For homes at the wildland edge, ask for a tempered lite in the assembly and have the installer explain how any laminated lite will behave near heat.
4. For noise, break-in concerns or sun fading, laminated glass adds value on top of its quake performance.
5. Confirm hardware weight ratings, glazing bite and sealant compatibility before the order is placed.

A good installer will answer each of these questions plainly. If the answers are vague, that is a sign to keep asking before any glass is cut or ordered.