For window covers - we found this material called Insul-Shine. It’s a reflective material on one side, and batting on the other. We just sewed some dark blue fabric on the opposite side and hung them on hooks. This way they are reversible. When we’re sleeping in freezing temps, we have the reflective side facing in which keeps the interior warmer and when we’re in hot temps, we flip them around so the reflective side faces the windows to keep the heat and sunlight out. They aren’t flushed on our windows to allow a bit of a gap to let the heat actually radiate and bounce off. when we are not using them, we just roll them up and velcro them above the windows. Best of luck to you brother!