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Windshield glass is often taken for granted in cars. Windshields give us an unobstructed view of the road and an added layer of protection from flying objects so we can stay safe. But what happens when your windshield is no longer safe? Can windshield glass spontaneously break? Why is it dangerous? And why can it happen? 

What is spontaneous breakage, and why is it dangerous? 

A broken windshield
A broken windshield | Getty Images

Spontaneous breakage is when something breaks without warning. In the case of windshields, it’s wildly unexpected since they are designed to be sturdy. As CBS News puts it, “Automakers say the windshield provides one-third of the structural integrity for the roof of your car.”

Not only that, but the pieces of glass falling onto a driver can be dangerous. The same CBS article recounts a case in 1999 where a woman was killed in a car crash. The impact of the crash threw her out of the vehicle along with the windshield. The glass shattered when it hit the ground, cutting her up as she lay on top of it.

While not all windshield breakage incidents can be prevented, there are some factors to keep in mind that could potentially cause a windshield to spontaneously break, especially if the window integrity is already compromised.  

1. Temperature 

Temperature can affect the windshield in many ways, especially when cracks already exist within the glass. It can happen with both heat and cold. 

In winter weather, water can get through cracks in the windshield, freeze, and expand. This can cause more cracking in the windshield. If water gets in the crack and freezes after that, the force may be great enough to shatter the windshield. 

Heat can have the same effect. According to MS Glass Outlet, “Extreme heat causes expansion. A crack or nick in your auto glass can grow as the glass expands under the heat.” They also add, “Too much heat on one side of the glass can cause the glass to expand on that side, but not the other. This process can cause bending, which can create tiny fractures in the glass.” Due to the minor fractures, the glass is more fragile and may shatter. 

2. Installation

According to CBS, “The problems [with windshields] don’t usually happen with a new car. It’s after someone replaces the factory-installed windshield incorrectly. That’s when the wrong adhesive could be used, or applied improperly.”

Installation is one of the main things that can cause a windshield to spontaneously break. While you may think this is only for DIY jobs gone wrong, this is not the case. 

Any windshield installer you go to may not be qualified. Underqualification is a significant problem in the industry, and they often don’t have formal qualifications or training. Unfortunately, this passes on to innocent consumers like you, who may have a faulty windshield without knowing it. 

This is not a cause for fear, though. You can find the right installers by checking if they meet AGRSS standards. AGRSS stands for Automotive Glass Replacement Safety Standard. It was founded by the Auto Glass Safety Council. This standard entails continual training of technicians, selecting the right glass, and more. You can trust that those who meet AGRSS standards are sufficiently qualified to replace a windshield

3. Inadequacies in the windshield glass

Inadequacies with windshield glass can manifest if the wrong type of glass is used for the windshield. According to WGME, laminated glass is sometimes used for only the front windshield, while the rear windshield uses tempered glass to cut costs. While laminated glass tends to crack, tempered glass is prone to shattering. Even a small impact could cause it to shatter suddenly, especially if it has already experienced some wear and tear up to that point. 


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