Comprising a steel space frame, it is the largest ETFE-clad structure in the world with over 100,000 m² of ETFE pillows that are only 0.2 mm (1/125 of an inch) in total thickness. The ETFE cladding, supplied and installed by the firm Vector Foiltec, allows more light and heat penetration than traditional glass, resulting in a 30% decrease in energy costs. This choice was made in view of Beijing's goal of presenting a fully "green" Olympic Games, with zero net growth in total carbon emissions. Likewise, the venue was also designed to "capture and recycle 80% of the water falling on the roof or lost from the pools."