Evans & Pearce floor ventilation systems for grain storage (http://www.evansandpearce.com/grain-cooling/floor-ventilation-systems) are built around plastic, twin wall ducting, which is a very robust and durable alternative to traditional metal systems. Our range of Polycool 6m x 450mm grain ducts feature a massive perforated area and, combined with solid EV fans, are more than capable of providing the air flow required to keep your grain crop ventilated.