A radiant barrier is a form of insulation topped with a reflective material designed to keep homes cool during hotter months. It is generally considered worth the investment if you live in a hot, sunny climate, as the cost can be recouped over time through lower energy bills. Installation costs typically range from $0.10 to $1 per square foot. After installation, homeowners in warm climates may save between $7 and $15 per month, potentially reducing their electric bill by 5% to 10%. The exact savings will vary depending on your location and the type of barrier chosen.

If you need to insulate behind finished walls, the best option will likely be to have an insulation professional install blown-in insulation. The installation requires small holes cut in your wall, after which the installer can blow loose-fill insulation into the void. After the installation, you’ll have minor drywall patching, which shouldn’t cost more than $100. Compared to ripping down the existing drywall, using a different type of insulation, and replacing and finishing the drywall, this should save you hundreds or even thousands, depending on the size of the room you’re insulating.

Spreading tin foil over your windows works similarly to radiant barrier insulation, but not as well. It will reflect some of the sunlight that would otherwise come through the glass and warm up the inside of your home, so it might help a little to keep your home cool in the summer. However, the appearance isn’t preferable to blinds or drapes that can offer the same benefits. You might also consider tinting your windows instead, which is a more aesthetically pleasing change that can still block a good portion of the solar heat coming through your windows.

Yes, you can install insulation behind drywall yourself, but only if your walls are not finished. If your studs are exposed, installing fiberglass insulation in roll or batt form is very straightforward and just requires a few tools and some safety equipment. If your walls are already finished and you’re looking to add insulation, it’s better to hire a professional, as you’ll likely need blown-in insulation, which can be dangerous to work with and a challenge to get into the proper areas in your wall voids.