Giant sunroofs expand interiors but can add weight and cut fuel economy
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Automakers may be obsessed with cutting vehicle weight, but they are happily packing on pounds in one place.
Giant sunroofs and skylights dominate many new-vehicle cabins. The treated glass provides natural light and can be as strong as steel. But the glass can add several more pounds than steel, depending on the size of the opening. And an open sunroof interrupts airflow over a vehicle, increasing drag and reducing fuel economy.
"What we're seeing is that more people are trying to bring more light and energy into the vehicle," said John Thomas, vice president at sunroof maker Webasto AG.
Webasto says it supplies about 55 percent of all original-equipment sunroofs used worldwide. Though sunroofs and skylights are getting lighter with the use of aluminum frames and thinner glass, Thomas said automakers carefully monitor the percentage of vehicles on which the features are installed.
If the heavier sunroofs make up more than a third of a vehicle's production mix, the vehicle's fuel-economy testing must include the feature.
Still, big glass has been a growing trend on the roofs of luxury vehicles for several years, and recent advances in sealing and mechanics seem to be expanding that trend.
The 2013 Lincoln MKZ, for example, will boast a retractable roof with more than 15 square feet of glass when it shows up at dealerships this year. For comparison, the two-piece sunroof that adorns Cadillac's SRX crossover measures just under 12 square feet.
Traditional sunroofs, like those that pepper the aftermarket, usually are less than 4 square feet.
Chrysler Group uses identical two-piece panoramic retractable sunroofs for its flagship sedan and SUV, the Chrysler 300 and Jeep Grand Cherokee. A $1,495 option on the 300, the roof's glass measures about 11 square feet.
At Hyundai and Kia, large sunroofs are widely available in various nameplates' upper trim levels.
Kia offers optional panoramic sunroofs on high-end trims of the 2013 Sorento crossover, 2012 Optima sedan and 2012 Sportage compact crossover.
Similar sunroofs are offered on Hyundai's Sonata mid-sized sedan, Azera large sedan, Veloster sporty coupe, Tucson crossover and the upcoming redesigned Santa Fe crossover and Elantra GT hatchback.
Ryan Beene contributed to this report
You can reach Larry P. Vellequette at lvellequette@crain.com.
