It reduces energy costs and also improves the appearance of siding. For example, it keeps vinyl siding running in a crisp, straight line by leveling the wall under the siding. It is made of closed-cell non-toxic EPS, which is 98% air and 2% plastic. Polystyrene is made of carbon and hydrogen. Styrene occurs naturally. Pentane is used to blow the product, which is not a CFC and is not harmful to the ozone layer. The product also protects against pests. www.progressivefoam.com