An energy control sheet, including a highly transparent substructure having first and second surfaces, a substantially transparent, thin film metal layer formed on one surface of the substructure, and a highly transparent thin film dielectric layer formed over said metal layer. The dielectric layer comprises a mixed metal oxide layer having metal constituents of at least one lanthanide series metal (e.g. cerium oxide) and at least one transition or semiconductor metal (e.g. tin oxide). The dielectric layer is characterized by substantial water vapor impermeability so that the weatherability of the energy control sheet is substantially improved. The metal layer is either a silver layer or a silver-palladium alloy.