Automotive glass must meet a host of government standards in the U.S. and elsewhere. It has to let in the maximum amount of light to help drivers see. It has to shatter into tiny pieces instead of shards that might hurt occupants in a crash.
But there are no requirements for sun protection. That can vary by vehicle, and even by window within a vehicle.
Read more: http://www.foxnews.com/leisure/2013/09/04/not-all-car-windows-protect-passengers-from-sun-rays/?intcmp=HPBucket#ixzz2eOpPaTIT