Originally Posted by blackout
I did something similar to that for $2 when I made my trip across the desert a few years ago.
Went to my Dollar store, bought 2 foam boards (used 1 1/2) cut to size.....
spray glued aluminum foil to the boards, held in place and closed the shade: VOILA !!!!
Worked great and the A/C had no problems, made a HUGE difference.