A common way to modernize arched windows is to install interior window treatments that allow light through the curved portion up to and let you cover the bottom portion for privacy. You can also install plantation shutters to make an arched window look more modern. From the exterior, arched windows can appear outdated if they’re coupled with ornate trim, so toning down the decor can make your window look more natural with a modern design.

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. 

Cellular shades, also known as honeycomb shades, are the most energy-efficient and insulating window treatments. Their honeycomb structure is made of soft fabric that forms layered cell pockets. These pockets trap air, creating a thermal barrier that reduces heat loss in the winter and blocks heat gain in the summer. For even greater insulation, consider double- or triple-cell varieties. Side-tracked cellular shades, which seal the edges of the window frame, can further minimize air leaks and maximize energy efficiency.

Tinting your windows will make your house darker since it will prevent some sunlight from getting inside. While you can choose a window film that is on the lighter side, there will still be reduced sunlight. If natural light is important to you, tinted windows might not be the best choice for your home.