Study On Moisture-proof And Energy-saving Of Compound Insulating Metal Roof

The implementation of building energy-saving and the improvement of building technology have forced the development of new materials,new technologies and new products in building field.The metal envelope system,which is insulated,light-strong,and easily assembled,is increasingly applied in long-span buildings such as airports.Inorganic porous fiber materials,such as glass wool,are often used as insulation materials for fire safety consideration.Based on the consideration of winter moisture prevention,a vapor barrier is set on the inner side of the insulation layer of the compound insulating metal envelope.In the south of China,however,this construction may cause internal condensation in summer in humid zones,which would have negative effects on energy consumption,safety and indoor air quality of buildings.In order to analyze the annual heat and moisture distribution of compound insulating metal roof in the whole year,and propose an optimal design scheme in consideration of moisture-proof and energy-saving,this thesis uses a combination of experiment and simulation to carry out research.The main contents are as follows:Firstly,the commonly used physical properties and test methods of porous building materials are summarized.With reference to relevant standards,the physical properties of glass wool were measured through corresponding experiments:the apparent density and porosity were measured by the vacuum saturation experiment,the thermal conductivity under different moisture content was measured by the steady-state thermal conductivity experiment,and the specific heat capacity was measured by differential scanning calorimetry experiment.The equilibrium moisture absorption experiment measured the isothermal moisture absorption curve,the water vapor permeability experiment measured the water vapor permeability coefficient,and the capillary water absorption experiment measured the water absorption coefficient and capillary saturation moisture content.The measured parameters provide basic material data for subsequent software simulation.Secondly,a scaled model of an air-conditioned room with a compound insulating metal roof was made,and the distribution of heat and moisture inside the components was tested from August 11 to September 8 in Chongqing.The results showed that during the test period,the maximum relative humidity inside the component was 89%.Although no condensation occurred during the test period,it is still possible that condensation may occur due to the different weather conditions during other periods of summer.The experimental results are validation of simulation.Thirdly,a one-dimensional heat and moisture transfer model of the compound insulating metal roof was set up in WUFI^?Pro software.The accuracy of the model was verified.One city was selected in per thermal design zone（representatively Harbin,Beijing,Chongqing,Guangzhou and Kunming）to simulate the annual heat and moisture distribution in the glass wool under the condition that the vapor permeability resistance of the vapor barrier was very small（0.1 m）and very large（1500 m）.The results showed that the temperature slightly fluctuated via applying vapor barriers with different vapor permeability resistance,but the relative humidity fluctuated significantly.When the vapor permeability resistance was very small,condensation was obvious in Harbin in winter.When the vapor permeability resistance was very large,a transient condensation occurred in summer in Beijing,while severe condensation occurred in summer in Chongqing and Guangzhou.When the vapor permeability resistance was set to different values,there was no condensation in Kunming throughout the year.Finally,the maximum relative humidity of the glass wool and the annual load caused by the heat and moisture transfer of the roof were simulated by changing the vapor permeability resistance（between 0.1～1500 m）of the vapor barrier in WUFI^?Pro.With the goal of preventing condensation and reducing the annual load,the analysis showed that the recommended values of the best water vapor permeation resistance of the vapor barriers in 5 cities are:Harbin and Kunming≥2 m,Beijing,Chongqing and Guangzhou are 0.3～0.5 m,0.3～0.6 m and 0.2～0.3 m,respectively.Finally,the recommended values were converted into corresponding common vapor barrier practices for engineering reference.