The design of the tower's glass façade, which completes a 120° twist as it rises, is intended to reduce wind loads on the building by 24%. This reduced the amount of construction materials needed; the Shanghai Tower used 25% less structural steel than a conventional design of a similar height. As a result, the building's constructors saved an estimated US$58 million in material costs. Construction practices were also sustainable. Though the majority of the tower's energy will be provided by conventional power systems, 270 vertical-axis wind turbines located in the facade and near the top of the tower are capable of generating up to 350,000 kWh of supplementary electricity per year, and are expected to provide 10% of the building's electrical needs. The double-layered insulating glass façade was designed to reduce the need for indoor air conditioning, and is composed of an advanced reinforced glass with a high tolerance for temperature variations. In addition, the building's heating and cooling systems use geothermal energy sources. Furthermore, rain and waste water are recycled to flush toilets and irrigate the tower's green spaces.
