The windshield of a vehicle is the front window. They are generally made up of laminated safety glass and a type of treated glass, which consists of two curved sheets of glass with a plastic layer (Polyvinyl Butyral(PVB)  laminated between them for safety, and are bonded into the window frame. 

Glass does an expectational job of insulating your vehicle that other materials like plastic can't  do. The design and shape of your glass is made to withstand not just wind, but road debris and outside elements like water and snow.