My objective is to reduce interior heat in my car while it's parked in an open lot in the direct sunlight all day. Option 1 - I could get one of those windshield things and put that up when I part the car. How much of a difference would that make? Option 2 - Tint Windows. Is this effective in reducing temperature? And to what degree? (significantly more than option 1 above) Are there types of tint material that are more effective, last longer, etc...? What are the downsides of tinting windows? Any other thoughts on the topic are welcome!