I recently saw a tip in a Facebook group and I tried it out for myself and it works!! I cut cardboard to fit the windows on the south side of my house (it happens to be the back of the house) and is where the Florida room is (for those of you who don’t know what that is, it is like a second living room). This is where I sit most of the time if watching TV etc. The south wall behind me is all windows. I have heat blocking shades but they are not enough. So I covered the cardboard with cheap aluminum foil, with the shiny side out and placed them in the windows. The shades cover them from the inside. Within 15 minutes of doing this, this room dropped 4 degrees in temperature! YAY!! Now, a room that used to be consistently 80 F. runs anywhere from 74 to 76 F. I am so happy!!