History of Weather Barrier
Derivated from USA, the history of weather barrier technique can be traced back to the middle of 20th century. Before that time, like most of the existing buildings in China up to present, people know little about the air tightness and water tightness relating to buildings. From the end of 1940s to 60s, people started to be aware of their importance. Professor Rowley from Minnesota University, USA, and Mr. Neil.B.Hutcheon from Canada National Building Standard Association both believe that the vapor condensation developed on the exterior wall and roof of the building has serious impact on the performance of building insulation material and the durability of envelope structure, leading to development of mold and damping problems…the liquid phase water (water) and vapor phase water (water vapor) penetrated into the envelope structure via the exterior air are the major cause of damping. Therefore, the architecture circles in America and Europe started to widely adopt a layer of damp barrier to have the whole building envelope by wraping it on the insulation layer, so as to increase air tightness and water tightness of buildings. But the damping problems of exterior building envelope are still not completely solved due to the non-permeability of the damp barrier.
In 1970s, with the outbreak of global energy crisis, the American and European countries paid more attentions to the energy conservation issues regarding to buildings, while the solution to the damping issue is of great significance in archiving the comprehensive energy efficiency. It was found through study by G.O.Handegord from Canada National Building Standard Association that the vapor shall travel from high temperature side to low temperature side due to the temperature difference across the envelope structure, accumulating and compensating at the insulation layer because of its failure to be vented due to the existence of damp barrier which is not permeable, thus resulting in the damping issue. As a result, people set forth a new requirement for the performance of damp barrier, that is, a material which is not only wind proof and water proof, but also can ensure the efficient discharging of vapor from the envelope structure is required.
In the mid of 1970s, DuPont company, USA, innovatively introduced its patent product Tyvek® into the building field. As an alternative product for the damp barrier, Tyvek weather barrier, with its unique performance in water tightness and permeability, allows the venting of vapor and at the same time improves the building’s air tightness and water tightness, effectively solving the damping problem. Since then, the weather barrier technique is rapidly accepted by people and is vividly called as “breathable membrane”. In additions to Europe and USA, it has been introduced to the areas such as Australia, South Africa, and Asia.
The application principle is shown in the drawings below:
Schematic drawing of weather barrier for exterior wall application
Schematic drawing of weather barrier for roofing application
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