Breathable membrane adopts the principle of microporous breathable, because the small diameter of water droplets and the diameter of water vapor there is a huge difference, water vapor can be diffused by diffusion principle through microporous membrane, liquid water or water droplets because of its surface tension, so that water molecules can not pass, also prevent the infiltration of water, so that the breathable membrane has a waterproof function.

Breathable membrane is laid outside the insulation layer, the whole building is covered, thereby reducing air leakage and convective heat loss, effectively strengthening the air tightness of the building. It laid outside the insulation layer, can ensure the effective discharge of water vapor in the enclosure structure, reduce the risk of roof dew, solve the problem of dew moisture, protect the insulation layer.