An interior view of the National Aquatics Center

(BEIJING, January 28) -- In spite of clear skies, Beijing, in the depths of winter, has a frigid coldness about it that can be attributed to strong winds from the northwest. The cold does not mitigate even as you stand before the National Aquatics Center admiring its beauty. Upon walking inside, however, you immediately feel the warmth of the building -- warmth that might remind you of pleasant springtime temperatures.

It turns out that the space between the air-pillow walls of the "Water Cube," as the National Aquatics Center (NAC) is also known, is completely sealed off, creating a layer of insulation.

In the summer, a meter-high vent works to regulate the NAC's temperature indoors through heat exchange, by drawing indoor heat out of and cooler outdoor air into the venue. In the winter the vent is sealed off, and the warm indoor temperatures remain constant.

To address potential problems with heat from direct sunlight, the membrane layers between the two layers of air pillows have different degrees of density to control the amount of sunlight that is let into the NAC. This works in part also to reduce the amount of heat brought about by the sun and helps keep the indoor temperatures under control.

According to Zheng Fang, head engineer of the venue's Chinese design partner, the design of the "Water Cube's indoor environment fully took into consideration the requirements of both athletes and spectators. The main competition hall and water recreation hall both make use of advanced ventilation systems.

Since construction began, the designers had monitored various parameters at the venue, including changes in wind pressure, wind movement and temperature field. This data has resulted in the ability to keep the venue's indoor temperatures constant year-round.