now , according to the present invention , functional coatings are provided that comprise both a porous inorganic layer and a polymeric filler . the porous inorganic layer comprises an inorganic material that can be formed into a layer at relatively low heat load . the polymeric filler fills the porosities in the porous inorganic layer , and can be , for example , wet coated onto the porous inorganic layer . the resulting functional coatings offer simpler and cheaper fabrication along with improved physical and optical performance .