How to distinguish the vapor barrier and breathable membrane
A vapor barrier for insulation is a moisture-proof plastic film that prevents condensation in various building insulation such as steel structure, timer frame structure, passive building etc.In commercial buildings or houses, the vapor barrier on insulation improves energy efficiency and living comfort as well as preventing the moisture.
The vapor barrier is widely used at the bottom of the insulation of buildings to prevent the penetration of indoor humid air into the insulation layer.The vapor barrier insulation can isolate water and air, and keeps the room completely airtight. So people use vapor barrier under the insulation layer in order to prevent indoor water vapor permeation into the building envelope.While breathable membrane is installed on the outside part of the insulation layer commonly, it is a kind of new product with both waterproof and breathable performance.Its function is to prevent outdoor rainwater to enter the insulation layer, and at the same time, it can discharge moisture from the insulation layer outwards to keep the insulation layer dry and increase the insulation performance of the building, thus making the building more energy saving.
But, in very wet areas, people also installed the roof vapor barrier as well as wall vapor barrier outside the building structure, this should be decided by the local installation codes.