I just got awnings installed two months ago on the windows that get sun for most of the day. It dropped the temps in those rooms by almost 8 degrees Celsius on hot days. The AC even runs less during the day now.
They're simple retractable awnings that a local guy installed for me. I used to hate the idea of awnings, but the thought about IR heat getting trapped clicked with me recently and suddenly the idea of awnings seemed brilliant.