Although windows amount to about 10 percent of a home’s surface area ... notes that Roman and roller shades do the best job at blocking sunlight but only provide “a small amount of insulation ...

Quilted roller shades and Roman shades with several layers of fiber batting insulate as well as block sun, and are more effective than other soft window treatments. Because of their individual ...

Possibly, though black cardboard fully exposed to sun is going to get very hot and be on the inside of the house (the goal is to block from between the window and the blinds). Syonyk[/url ...