A radiant barrier is a type of building material designed to reduce heat transfer. It typically consists of a reflective surface, often made of aluminum, that reflects radiant heat away from living spaces. This helps keep homes cooler in the summer and warmer in the winter, improving energy efficiency. Radiant barriers are commonly installed in attics, where they can significantly lower cooling costs by preventing heat from entering the home. They work best in hot climates and are often used in conjunction with other insulation materials to enhance overall thermal performance.