The material covering the exterior walls is known, but it does not fit any of the definitions found in this table.

EWO_China_Brzev_1

EWO_China_Brzev_2

Exterior shell (walls and the roof) of the National Swimming Center in Beijing, China is made of a 0.2 mm thick plastic Teflon-like foil, which simulates bubbles (S. Brzev)