When there are higher requirements for building effects, ETFE air pillows are generally chosen for heat preservation. The roof of Shenzhen Wanghai Primary School uses ETFE air pillows for an architectural design because of its ideal shading effect.

The thermal insulation principle of the air pillow is similar to that of hollow glass, and it mainly depends on the air layer. The thickness of the air layer has a great influence on the thermal insulation capacity.

Take insulating glass as an example, when the thickness of the air layer is less than 5mm. The heat transfer process is dominated by heat conduction and convection heat transfer. When it is larger than 5mm, the main heat transfer is radiation.

When the thickness is 0-20mm, the thermal conductivity changes very significantly. At 25~70mm, the thermal conductivity changes very slowly. And the peak appears at 20mm.

For insulating glass, increasing the thickness of the air layer means higher cost. The air pillow is different. Air pillows will lose height due to the consideration of material bearing capacity. The customary practice in the industry generally loses height of one-tenth of the span.

Therefore, in a large span, the air pillow has a thicker air layer than the insulating glass, and this will basically not affect the cost, on the contrary, it will be better to improve the thermal insulation performance.