I have huge windows that allow enormous amounts of sunlight in. And it gets hot as all can be in here. Contact paper is out of the question. The mess to take off in the winter would be crazy due to wanting the sunlight in the winter. I found rolls of solar screen 48" x 25 ft. at Home depot online, for $78. Now, that’s just the roll, and I’m not paying $200-$300 per window (which is 48" X 80") for a custom made screen. Do you think I could simple use double sided tape to hold them up against the windows for the summer. I only want to cover 2 windows. And the whole entire window won’t be covered, just the middle. I have two small windows on the side that I want to be able to open. The curtains I have will be enough to cover those. I’m not too worried about looks. Just an extremely cheap and effective way to prevent this insane heat. I am home improvement illiterate! Sorry and THANKS!!!!
My windows are very small, so I have to use very small air conditioners, 5000 b.t.u. I know those are large windows but the parts that actually open are very small. It is an old home and the other windows are just as small. I do plan on installing 2 more in the house since it is all open, even the upstairs to the downstairs, I would like to take care of the excess heat coming in first. So hanging with double sided tape would work you are saying, correct?

you have a very good idea also look into thermal sided drapes. keeping the sun out is the main objective. ceiling fans and air conditioners with very high btu’s help also, good luck.