This is an auto glass pandemic that’s affected almost every automaker — 2018 models representing 35 brands have at least one sunroof-shattering incident.

Auto Manufacturers Blame Projectiles

There’s not a single uniform response that all automakers have put forth, but most manufacturer’s explanations are similar when drivers contact them about shattering sunroof glass. Automakers usually blame projectiles — stones or other debris — that strike the sunroofs while traveling at high speeds.

Striking debris certainly can cause auto glass to shatter when driving at highway speeds, which is when most of these incidents occur. This explanation, however, fails to account for all of the mounting evidence.

There is a clear increase in the frequency with which sunroofs are shattering, and flying stones doesn’t explain why. There can’t be a 71-percent increase in the number of stones flying around.

Thinner Metals Offer Another Explanation

An alternative and more plausible explanation arises from the metals being used in vehicles.

Over the past few years, automakers have been using thinner metals as a means of reducing vehicles’ gross weight and improving their fuel economy. It’d be unfair to single out any one manufacturer as an example because this appears to be an industry-wide issue. There are many instances where automakers have built models with lighter, thinner metals when the models were last updated (which was normally within the past 6 years).

There’s not definitive proof yet, but an unintended consequence of using thinner and lighter metals may be a loss of support for attached glass. Even if the metals are stronger (which automakers claim in some cases), they might not offer the same bracing for glass.

Whether this could lead to spontaneous shattering due to manufacturing defects, less flexible glass that’s worn down by wind or glass that can’t handle the occasional flying stone is unknown. Whatever the link, it’s plausible — and perhaps likely — that the thinner metal automakers are using is contributing to the increase in shattering sunroofs.

Drivers Should Check for Recalls

Shattering sunroofs, of course, pose a potential safety hazard. The risk is low — just 859 incidents have officially been reported and there are many vehicles with sunroofs. It’s a present risk, though, and one that drivers should guard against.

To see if there’s anything you should do about your vehicle’s sunroof glass, check whether there are any recalls on your vehicle. Some automakers have issued voluntary recalls. If there is a recall, have a qualified professional do the work. The cost should be covered by your vehicle’s manufacturer.

Drivers Don’t Need to Worry About Windshields

Many drivers naturally have concerns about their vehicle’s windshield when they first hear about sunroofs shattering. Thankfully, there’s little reason to be concerned about windshields shattering in the same way.

Windshield glass is made differently from sunroof (and exterior mirror) glass. Sunroofs and exterior mirrors are made from tempered glass, which shatters into small, rounded pieces when broken. Windshield glass is laminated glass, which is entirely different. It’s made of two sheets of glass that are held together by a layer of vinyl. Laminated glass will break — but the vinyl will keep the glass in a solid sheet even when it shatters.

Thus, windshields almost never (if ever) shatter into little pieces that go flying in drivers’ and passengers’ faces.