Auto Glass: School Project

Question
Good evening, I have some questions for an engineering project, not about my car.  I must design a simple, inexpensive, yet effective product that can be used to keep car/bus windows from letting in cold air.  However, I have no prior knowledge on windows at all.  I understand that you specialize in car windows.  I have a few simple questions that I am unsure of so I was wondering if you could help me in any way.  What glass is generally used for transportation systems and why?  How does the cold air reach the inside of the window on a car/bus?  Does it have to do with the transparency of the glass?  Would a thicker substance make it harder for cold air to get through?  Does the air get through the sides of the windows?  Are the windows even the problem or is it the insulation?  Again, I understand that this may not be relevant to what you specialize in, but I would highly appreciate you informing me on anything else you know about windows, heating, cars/buses, or any ideas for my project.  If you can’t help do you know anyone who I can contact who can? Thank you so much for your time and consideration.

Answer
Hello Claire,

I think your instructor needs to assign you a different project.  

Windows on today's vehicles do not allow air to enter the vehicle when they are closed.  Vehicles today are so "tight" that almost every vehicle incorporates an automatic ventilation feature that brings a small amount fresh air into and out of the vehicle even when the passenger heating or cooling system is in the off position.

During summer or winter there is some heat gain or heat loss due to the low "R" value of auto glass, but your project calls for a "simple, inexpensive" solution.  Improving the "R" of auto glass would be neither of those.

Good luck with your assignment.  Feel free to send me a follow up question if you like.

Ben ... the power window guy