this invention discloses improved residential roofing products with durable active protection against algae discoloration . versatile organometallic salts and chelates for this purpose are incorporated in manufacture of composite concrete tile and asphalt shingle products via integrated process modifications . these chemically stable non - volatile microbiocides , with exceptional effectiveness against both green and blue green algae , are tailored for specific matrix compatibility . by virtue of their composition and surface activity they serve a dual function in process improvement and product performance . the control of microbiocide activity , long term , significantly advances the state - of - the - art protection against algae and the service life of these products .