I saw your story on whether insurance covers shattered sunroofs and I was left with the question: How often does this actually happen? I have an SUV with a big panoramic sunroof. Should I be worried about it? – Rosa, Toronto
If you have a panoramic sunroof, don’t be too worried about danger from above, Transport Canada says.
“Though the number of shattered sunroof complaints are rising, when you consider the number of vehicles on the road, it’s still quite a rare event,” Sau Sau Liu, a spokeswoman for Transport Canada, said in an e-mail.
Since 2000, there have been 878 complaints to Transport Canada of sunroofs shattering – that’s an average of about 40 a year.
Until 2011, they were relatively rare – there were 18 complaints from 2000 to 2011. But from 2012 to 2022, there were 860.
The rise coincides with an increase in panoramic sunroofs and moonroofs – the terms are interchangeable these days – over the past decade or so.
Transport Canada said it determined that gravel was the culprit in most cases – even if the actual break came later.
“While the cause could not be confirmed in all cases, Transport Canada’s investigations concluded that the majority of incidents were the result of external damage from impact with an airborne projectile, such as a piece of ice, gravel or other debris, hitting and damaging the glass,” Liu said. “The glass could break on impact, or at a later time with temperature shifts or a vehicle jolt. Such breakage is more prevalent in provinces where gravel road treatments for ice/snow and severe temperature shifts are common.”
Sunroof glass can also be weakened if scratched when loading or unloading a roof rack, Liu said.
There have been no reports of serious injuries, Transport Canada said on its website.
Temper, tempered?
Drivers who’ve had their sunroofs shatter have said it’s happened suddenly with a loud bang and a shower of small glass chunks,
Meaghan Maloney, a London, Ont., woman whose 2023 Nissan Rogue’s sunroof shattered last month while she was driving told CTV News that the explosion was “quite shocking.”
“It wasn’t until I heard the wind that I looked up to see the sunroof was gone,” Mahoney said.
Sunroofs are typically made of tempered glass – known as safety glass. It’s about four times stronger than ordinary glass and shatters into small, relatively harmless pieces instead of into sharp shards. The glass is strengthened using either heat or chemicals.
Typically, shattered sunroofs aren’t covered by the manufacturer’s warranty because car makers say they weren’t caused by defects.
But defects can happen and can be tough to detect, a glass expert said.
“Contaminant inclusions in glass, like nickel sulphide, are a common issue for tempered parts and are very difficult to detect at manufacture,” said Chris Davies, head of research and innovation for Belron Canada Inc., the parent company of Speedy Glass. “The change in the crystalline structure of these inclusions creates significant stress and can lead to sudden failure.”
In the United States, there have been class-action lawsuits filed against several auto makers, including Hyundai and Mercedes, alleging that shattered sunroofs were because of a manufacturing defect.
One option to prevent sunroofs from shattering explosively would be for auto makers to use the more expensive laminated glass – two pieces of glass held together by a middle layer of polyvinyl. It’s used in windshields. While it can still break, when it does, the pieces stay stuck to the middle layer.
“Laminated glass [sunroofs] may reduce contaminant-based failure because they are not rapidly cooled which causes the problematic crystalline structures that add very high stresses,” Davies said. “Of course, if the failures are due to stone impacts, while damage frequency may not be eliminated, the failure won’t be explosive like in the case of a tempered part.”
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