Damages due to humidity transfer in porous materials

Abstract

The basic idea of this work is based on the dependence of the biological damage due to amount of moisture in the building. The larger the average amount of humidity is, the better the growing conditions are for insects, bacteria and fungi. Therefore, the number and scale of damages on wooden structures or visible mold growth is in a close context, respectively is directly related to the amount of long term moisture in buildings.In frame of the dissertation, evaluations of structural investigations - pointing to humidity occurring in masonry structures - were done in elderly residential buildings. After then, the results were classified. The basis of that work are 97 detailed own investigation reports regarding damages caused by wood-destroying fungi and damages caused by moisture. In accordance of the results of investigations of 4,481 heads of wooden floor beams in old apartment buildings, it is shown, that the degree of damage - coursed by wood-destroying insects and fungi - of these wooden heads are on an average level of 23.9 %. In absolute terms it equates to a rate of 1,070 wooden beam heads. The distribution of damages varies, depending on the direction, the wall cross-section and type of execution.The effect of solar influence on the drying behavior of the outer wall is very clear. On the southern walls, there were detected 131 damages to the wooden ceiling beams, caused by ambient conditions and 212 on the north facade. The permanent exposure to moisture in the timber heads on the shady north face thereby is causing an about 60% higher rate of damage.The analysis also shows that already a small increase of the wood humidity in the edge region of the outer wall from 9.7 % up to 11.1 % leads to an increase of damage rate of the heads of the timber beams to in average 4.5 %.With help of thermal and hydrological simulation calculations of distribution of moisture in the components under natural boundary conditions it is currently not possible to draw sufficient conclusions to realistic contents of water in the wall cross-section. Thus, the long term dampness behaviour in buildings with timber joist floors and low changes of humidity rates cannot be assessed adequately.

The basic idea of this work is based on the dependence of the biological damage due to amount of moisture in the building. The larger the average amount of humidity is, the better the growing conditions are for insects, bacteria and fungi. Therefore, the number and scale of damages on wooden structures or visible mold growth is in a close context, respectively is directly related to the amount of long term moisture in buildings.In frame of the dissertation, evaluations of structural investigations - pointing to humidity occurring in masonry structures - were done in elderly residential buildings. After then, the results were classified. The basis of that work are 97 detailed own investigation reports regarding damages caused by wood-destroying fungi and damages caused by moisture. In accordance of the results of investigations of 4,481 heads of wooden floor beams in old apartment buildings, it is shown, that the degree of damage - coursed by wood-destroying insects and fungi - of these wooden heads are on an average level of 23.9 %. In absolute terms it equates to a rate of 1,070 wooden beam heads. The distribution of damages varies, depending on the direction, the wall cross-section and type of execution.The effect of solar influence on the drying behavior of the outer wall is very clear. On the southern walls, there were detected 131 damages to the wooden ceiling beams, caused by ambient conditions and 212 on the north facade. The permanent exposure to moisture in the timber heads on the shady north face thereby is causing an about 60% higher rate of damage.The analysis also shows that already a small increase of the wood humidity in the edge region of the outer wall from 9.7 % up to 11.1 % leads to an increase of damage rate of the heads of the timber beams to in average 4.5 %.With help of thermal and hydrological simulation calculations of distribution of moisture in the components under natural boundary conditions it is currently not possible to draw sufficient conclusions to realistic contents of water in the wall cross-section. Thus, the long term dampness behaviour in buildings with timber joist floors and low changes of humidity rates cannot be assessed adequately.