Study on the Concept of “Breathable”Building by Domestic Building Circle
With the requirements for the building energy conservation and residential quality becoming increasingly higher in our country, the concept of making the building “breathable”, that is windproof, waterproof and air permeable, has already gained people’s attention, and benefit studies and practice have been made, though the weather barrier technique was just introduced into the domestic market 2 years ago whose concept is far from being popularized in our country.
As far as the wall, as a matter of fact, regulations concerning the necessity and methods for the waterproof and air permeability of walls (or damp proof and air permeability) have already been established in the country. The famous thermo physical scientist Mr.Chen Qigao from the Building Engineering Institute of Chongqing University, started to study the theory of heat and dampness migration in 1980s, pointing out in a number of essays that the dampness and air penetration have serious impact upon the performance of insulation layer, endurability of envelope structure, indoor air quality and building energy consumption, with effective solutions provided. In his book titled theory on calculation and design of heat and dampness migration within the building envelope, he put forward that the vapor barrier provided on the higher temperature side (inner side of envelope) can only solve par of the damping issue…lower temperature side is required to be provide with an air layer absorbing the dampness out of the layer of heat insulation material (insulation layer) to ensure the permanent dry condition of the heat insulation layer (insulation layer)”. Besides, he added that outside the insulation layer, the windproof paper is required to eliminate the internal penetration of air within the heat insulation layer (insulation layer), but it is advisable to use the paper which is vapor permeable and is not air permeable by large quantity ”. Such statements are completely consistent with the weather barrier theory. Ideal result also obtained in his consequent engineering practices based on such theory.
As far as the roof, regulations on inverted roof were already made in Chinese national standard Specification of Roof Engineering Construction and Acceptance (GBJ207-83) in 1980s. The rapid popularization of the inverted roof method in recent years shows that people is beginning to attach importance to the issue of dampness protection and air permeability. In the roof (88J5-1) developed by North China Standard Office, it is addressed that through the analysis based on the investigation and study, maintaining the roof insulation layer in permanent dry condition is of great importance to the insulation effect on the roof, while the inverted roof method which places the insulation layer upon the waterproof layer is good for maintaining the drying out of roof insulation layer. From that, people have already considerably realized the dampness proof and air permeability of roof. To sum it up, although the weather barrier technology in China is in its starting period, people has already been aware of the wind proof, water proof, air permeability which shall be attached great importance by the building circle with the deepening of requirements for energy conservation and environmental protection.
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