It may actually make the problem worse by absorbing and holding the heat longer. Foil blocks 95 percent of the radiant heat from the hot roof. I installed it in my attic and it dropped my bedroom temperature by 10 degrees. Attic radiant barrier foil is basically the same type of aluminum foil that you use in your kitchen. For durability and easy installation, attic foil is thicker and reinforced with nylon mesh or kraft paper.
Attic foil is very easy to install.
Simply staple it to the underside of the roof rafters. The neatness of the job is not important for it to be effective. It took me about two hours to do a 30 ft. by 50 ft. Do it in the evening or in the early morning when it is cooler. The lightweight aluminum foil is often available in four-foot wide rolls from 50 to 100 feet long.