3 ply roof underlay membrane is also called breather membrane, with high performance and top combination of fabric and membrane, make the film inside not only perform the function of waterproof, but also the function of breathe. Nantong Kangda, the first company in China to produce this produce, has developed this product for many years, the technology we obtained now is the advanced, and has been proved by many Lab. 

The job of a breather membrane is to stop these impurities from adversely affecting the building, but in order to carry out this task without suffocating the building, they need to be breathable. If polythene was used for example as an external protection lining, then this would make a great barrier against adverse external environmental conditions, but naturally occurring moisture produced from within the building would quickly become trapped in the interstitial layers causing untold damage.