The “Water Cube” is a rectangular-shaped steel building covered by a membrane of brightly lit blue bubbles which is incredible to look at but it is also important on an environmental level. The Water Cube consists of 100,000 sq m of ETFE, (Ethylene Tetrafluoroethylene) a unique transparent plastic which absorbs solar radiation and reduces thermal loss. It is the world’s largest and most complex EFTE building ever constructed. EFTE is recyclable and light (1% the weight of glass) but it is also strong, capable of bearing up to 400 times its own weight. As it lets in more light and is a better insulator than glass it will reduce energy costs in the Water Cube by 30%. The Water Cube’s structure consists of 3,000 pneumatic cushions ranging from with different sizes from 9sqm to less than 1sqm in size. These “air bubbles” are relatively independent of each other so they can be easily replaced. The LED-lit bubbles allow warm air to enter the building and keep the water temperature at an optimum 28 degrees, but the air can also be stored and used in the Water Cube when required. The Water Cube spans 80,000-sq-m and was constructed with 6,700 tons of steel, but as EFTE spans greater distances than glass it needed less supportive steel structure beneath it.