Do not use Windex or any glass cleaner when applying window film. These products contain ammonia, which will damage the film. Instead, use the application solution provided with the installation kit. If there is no solution, make your own using 1 teaspoon of baby shampoo and a gallon of bottled water.

To darken your windows without curtains, try installing window film or even installing an awning outside your windows. Window film is a DIY-friendly option with many different darkness levels you can choose from to fit your desired look. Awnings can also help by casting shade over your window, though this isn’t feasible for every home. 

You can easily and cheaply use tin foil or cardboard to black out your windows. Save a pretty penny by cutting either material to the size of your windows and taping it to the window. This is one of the easiest and most budget-friendly blackout solutions, but it definitely isn’t the most aesthetically friendly.  

Some frosted glass sprays can handle the outdoors, but most of them aren't built for it. Sprays made for exterior use will say so clearly on the label. Anything marked “interior use only” can't hold up against rain, UV exposure, or changing temperatures without peeling, fading, or yellowing. Outdoor-rated sprays are typically more durable, but even then, proper prep and application matter. Before spraying anything outside, double-check the product instructions. If it doesn’t specifically mention exterior use, skip it.