Research On The Mould Germination Risk In Building Wall In The South Of China

Chinese onstruction industry developed rapidly but roughly in recent decades,and there are some problems in the building environment.Usually,the temperature and humidity are pretty high in the South of China.Consequengtly the mould germination risk is great in the building environment,and the mould germination inside the wall is often overlooked.A evaluation model was developed for mould germination risk based on the transient temperature and humidity distribution in the building wall,and then a series of studies for the mould germination risk were carried out on the two typical building walls in the South of China.Firstly,based on a comprehensive literature studys on prediction of mould growing,mould contamination in building and heat and moisture(HM)transfer in wall,the correlation between mould germination and HM transfer of building wall was discussed.Secondly,the main hazards of mould contamination to human body and buildings were described.The conditions for mould germinating and growing were analyzed.By the scanning electron microscopy,the interior structures of some common porous building materials were observed.Taking Hunan Province of example,investigation of the mould contamination in building environment was conducted.Thirdly,a full-size experimental platform for the coupled heat and moisture transfer in building wall was built up.The experimental platform includes two experimental houses and two experimental walls,and it can carry out two kinds of experiments,one is the kind of experiment that tests the heat and moisture transfer under a artificial environments,and another is for the experiment that under actual climate.The experimental wall is the aerated concrete wall.Experiments of the heat and moisture transfer in building wall were carried out,and the results were offered to validate the mathematical model.Fourthly,based on the laws of conservation of energy and mass,taking temperature and relative humidity as driving potentials a coupled heat and moisture transfer model was developed,which takes vapor transfer,water transfer and the phase change between them,the interaction between heat transfer and moisture transfer,and the solar radiation into consideration.The relative humidity is selected as the driving potential,which avoids the discontinuity problem of moisture content at the interface of two different materials.Then the coupled model was solved.The hydrothermal model was validated by compared with the benchmark test of EN15206,HAMSTAD projects and the experimental data.The results show that the simulation results are in very good agreement with the results of the benchmark test of EN15206 and HAMSTAD project.The simulation results agree well with the experimental data as well.Lastly,an evaluation model for the mould germination risk based on the transient temperature and humidity distribution in the wall was developed.The method was used to evaluating the mould germination risk of the typical walls(red-brick wall and aerated concrete wall)in 93 cities of the South of China.The effect of solar radiation,indoor temperature and indoor humidity on the mould germination risk were studied.Three concepts(critical value of relative humidity,critical temperature and humidity,the critical line of temperature and humidity)about the mould germination risk of building wall were proposed.Some critical lines of temperature and humidity of indoor air are obtained at the internal surface of wall in the major 15 cities of the South of China.With these researches we can find that:(1)Literature researches reveals that,these existing models for predicting the mould growth are less suitable for directly predicting mould germination in building wall exposed to actual climate,and humidity is the critical factor for mould germinating and propagating.It is necessary for studying the coupled heat and moisture transfer in typical building walls,and then studying the mould problem in the South of China;(2)By Scanning electron microscopy,the interior structure of some common porous building materials was observed,and it can find that there are rooms for mould germinating in these materials.The results of the questionnaire survey show that there is serious mould contamination in building environment in Hunan Province.There is a strong correlation between mould contamination and building wet conditions.And there is also a strong correlation between mould contamination and disease risk of resident;(3)The mould germination risk of the two typical building walls was evaluated,and the results show that:the mould germination risks of these cities of the South of China are often different,as the same as the risks between the two typical walls,and the risks between different place of the wall;(4)The effects of solar radiation,indoor temperature and indoor humidity on the mould germination risks are great.The lower solar radiation results in a greater mould germination risk.The rising indoor humidity results in a rising mould germination risk of the wall.Indoor humidity has a greater effect on the internal surface than on the outside interlayers.The rising indoor temperature results in a decreasing mould germination risk at outside interlayer,but an increasing risk at the internal surface;(5)Changing the temperature with step length of 0.5 ?,and changing the relative humidity with step length of 0.1%,the critical lines of temperature and humidity for mould germination risk at the internal surface in the major cities of the South of China were built up.The results show that the critical lines are different for different cities.And the critical lines are different for different wall.The fullsize experimental platform for the heat and moisture transfer in building wall,and the coupled heat and moisture transfer model lay the foundation for studying the hydrothermal transfer characteristic in building wall in the South of China.The evaluation of the mould germination risk of the two typical walls,the built critical lines of temperature and humidity for the mould germination risk,and the survey of the mould contamination status in the building environment in Hunan Province,lay the foundation for optimizing the building environment in the South of China.