Cutting energy bills the Victorian way

Modern facades on Victorian buildings in Chicago and other industrial cities of the American Midwest often hide a secret. Scattered through old drugstores and boarded-up banks from Madison to Fort Wayne, curiously shaped glass tiles known as Luxfer prisms lie just a few centimetres behind the paint and plaster. Luxfers were one of the 19th century's greatest innovations in lighting, and an idea that is beginning to make a comeback in our own energy-conscious times.