Why Do North America’s Sunroofs Keep Exploding?

Why Do North America’s Sunroofs Keep Exploding?

Across the US and Canada, demand for sunroofs in new vehicles has exploded, particularly within the past four years. No longer reserved solely for luxury vehicles, nowadays sunroofs feature prominently in virtually all makes and models of vehicle over a broad range of price points. In tandem with the trend, however, incidences of sunroofs exploding – quite literally and seemingly without cause – have skyrocketed over the same period.

In fact, sunroofs have exploded in every region of the US, and in every month of the year. Self-reported data from the National Highway Traffic Safety Administration (NHTSA) Office of Defects Investigation indicates a steady rise in the number of reports through 2012, followed by a spike in cases reported in the US from 2013 onward.

Similarly, Transport Canada reported no such complaints in 2007, but more than 110 were registered in Canada in 2016 and 103 as of October 16, 2017. The agency ascribes the boost in consumer complaints in part to the increased number of vehicles on the road with sunroofs, which are also of increasing size, compared to a decade ago.

Though the incidents span a wide range of motor vehicle brands, NHTSA has only investigated the Kia Sorento for model years 2011-2013. A similar Transport Canada investigation led to the recall of over 10,000 of the SUVs in March of 2016.

While the odds of any one sunroof exploding are relatively low (a tire is more likely to blow out than a sunroof), these incidents are nevertheless dangerous. Though the shower of tempered glass on vehicle occupants should be minimally damaging in and of itself (as tempered glass is designed to break with rounded, rather than sharp, edges), the sudden noise and ensuing shock can cause the driver to drive erratically, endangering occupants, other vehicles, and pedestrians.

Shattering Expectations

While the number of reported sunroofs exploding in the US and Canada has increased significantly in recent years, the exact reasons remain up for debate. Possible causes include:

  • the large size or curved shape of some sunroofs, which make them more vulnerable to damage from projectiles and other debris kicked up from the road
  • materials concerns or contamination, such as the presence of contaminant nickel sulfide in tempered glass formulations or the application of coatings that weaken the glass
  • thermal shock, i.e., expansion and contraction of the glass due to sudden fluctuations in ambient temperature
  • weakened structural integrity as a result of the impact from bumps in the road and twists in the car’s frame
  • imperfect manufacturing processes

Material Quality & Safety Standards a Concern

Glass in passenger vehicles produced in the US is required to meet the minimum standards put forth by the American National Standards Institute and the society of automotive engineers SAE International.

But these standards haven’t been updated since 1996, and since that time sunroofs have gained both in popularity and in size.

Due to pressures to keep down vehicle costs and overall weight, manufacturers typically use tempered glass in sunroofs at the thinnest thickness permitted. While tempered glass may be sufficient when a sunroof is small and flat, it poses a potential safety hazard when sunroofs are large and curved, as they are with trendy panoramic sunroofs that have become increasingly common in recent years.

Room for Improvement

Though tempered glass sunroofs meet the qualifications of the standards currently in effect, research shows that laminated glass sunroofs may be key to to a safer riding experience.  Laminated glass, which comprises two panes of glass fused by a sheet of plastic, is more likely to hold its form and less likely to shatter into the cabin when broken than tempered glass.

To Find Out More

Interested in learning more about the North American automotive industry? For historical demand data and forecasts by product, performer, and country, see The Freedonia Group’s series of studies on the automotive aftermarket, which includes:

These studies also cover market environment factors, industry structure, company market share, and leading companies.

About the Author

E. Reta Sober is an industry analyst at The Freedonia Group where she writes studies related to electrical equipment, machinery, and the automotive industry.