Stucco is a siding material made of Portland cement, sand, lime and water. Applied in three coats over a lath base, it provides a solid, durable and seamless home exterior. Another advantage is that it’s naturally resistant to fire. Stucco over Styrofoam is also called EIFS (exterior insulation and finish system), and it’s a popular alternative to stucco. An acrylic-polymer coat is sprayed or applied onto a base of fiberglass mesh and foam board insulation. It virtually never cracks and gives your home extra insulation.