A coating on an architectural building material is formed by particles of a polymer that are softened using heat and allowed to cool over the surface of the building material to form a cohesive and adhesive structure or film on the building material. The polymeric coating composition is substantially free of any volatile organic compound (VOC). A system for applying coatings on architectural building materials includes an apparatus for spraying a polymer emulsion on a building material, an apparatus for removing a carrier from the polymer emulsion, and an apparatus for conveying the building material from the spray apparatus to the apparatus for removing the carrier. A method of coating an architectural building material includes spraying a substantially VOC-free emulsion having particles of a polymer onto the building material. A volatile portion of the emulsion is flashed off. Heat is then used to coalesce the particles of the polymer.