Rematerialization and cradle-to-cradle design can be applied with high-tech or low-tech methods to new or existing buildings. Harmful materials in existing buildings can be replaced with healthful ones. Old buildings can also be restored with new designs and technologies that harvest the sun’s energy – examples include the Audubon Society’s century-old headquarters in Manhattan and the venerable Field Museum in Chicago – or flexibly refitted for a variety of new uses.