Among world's sport facilities, the National Stadium has one of the largest spans in its steel structure. Its roof maintenance structure is a steel structure covered by two layers of membranes: the upper layer is a transparent ETFE membrane fastened between the upper chords of the steel structure; the lower layer is a translucent PTFE acoustic suspended ceiling fastened under the lower cords of the steel structure and to the side walls of the inner loop.
    The National Stadium was constructed with an advanced energy-saving design and such environment-friendly features as natural ventilation and lighting, full recycling of rainwater, utilization of renewable geothermal energy resources and application of solar photovoltaic power generation technologies. Under the football field of Bird's Nest are 312 GSHP (ground source heat pump) wells, which heat the Stadium in winters by absorbing thermal energy from the soil through embedded heat exchange pipes; and cool the place in summers by absorbing cold energy from the soil, saving considerable amount of electric power.The roof of Bird's Nest is equipped with a special rainwater recycling system, through which rainwater is collected for watering plants and grass, flushing toilets, fire fighting and even washing the tracks. These advanced environmental-friendly measures have turned the National Stadium into an enormous "green building" that lives up to its name.