In 1868 and 1869, Josef modernised the furnaces at the Neuwiese and Polaun glassworks – they were no longer heated by wood and switched to wood gas. Josef was the first to incorporate the groundbreaking regenerative flue gas heat recovery system (first using wood, later using coal) to heat his glass furnaces. This new technology was invented by German engineer Friedrich Siemens between 1856 and 1861 and translated into a saving of 30-50%. In 1878, a competitive (but similar) system from Siebert (patented in 1878) was incorporated in Riedel's factories.