Impact of wind-driven rain on historic brick wall buildings in a moderately cold and humid climate: Numerical analyses of mould growth risk, indoor climate and energy consumption

This paper gives an onset to whole building hygrothermal modelling in which the interaction between interior and exterior climates via building enclosures is simulated under a moderately cold and humid climate. The focus is particularly on the impact of wind-driven rain (WDR) on the hygrothermal response, mould growth at interior wall surfaces, indoor climate and energy consumption. First the WDR load on the facades of a 4×4×10 m3 tower is determined. Then the hygrothermal behaviour of the brick walls is analysed on a horizontal slice through the tower. The simulations demonstrate that the impact of WDR loads on the moisture contents in the walls is much larger near the edges of the walls than at the centre. The obtained relative humidity and temperature at the interior wall surfaces are combined with isopleths of generalised spore germination time of fungus mould. The results show that WDR loads can have a significant impact on mould growth especially at the edges of the walls. Finally, for the case analysed, the WDR load causes a significant increase of indoor relative humidity and energy consumption for heating.status: publishe

X-ray CT and digital volume correlation of Tuff stone under uniaxial compression

International audienceWe present X-ray CT of a dry or wet tuff stone specimen under uniaxial compression. The obtained CT data were analyzed using a digital volume correlation software to determine the displacement and strain fields

Periodic alternation between intake and exhaust of air in dynamic insulation

Dynamic insulation (DI) can recover heat lost in conduction by drawing cold outdoor air into indoor through an insulation wall in winter. A “breathing DI” system we proposed in the past has functions both as an insulated envelope and as a highly efficient heat exchanger for ventilation. It is alternated periodically that the outdoor air is drawn through half of walls made of breathable inorganic concrete (BIC) and the indoor air is exhausted through the other half of the BIC walls. In order to put the breathing DI system into practice in housing construction, this paper presents some studies from various points of view in addition to the past studies on heat and moisture transport based on laboratory experiments and numerical simulations. We first experimentally studied the filtering efficiency and clogging of a BIC panel. This showed that approximately 30 % of the atmospheric dust can be captured by a BIC panel and no clogging would occur for at least 10 years. We also measured the sorption and desorption of formaldehyde by a BIC panel to confirm the effectiveness of a BIC wall to sorb gaseous state formaldehyde. We furthermore constructed a new test house at Ibaraki, Japan, to confirm the thermal performance of the breathing DI system based on full scale experiments

Impact, absorption and evaporation of raindrops on building facades

In this paper, the impact, absorption and evaporation of raindrops on building facades is investigated by experimental and numerical means. Laboratory experiments were carried out to study the impact of water drops with different diameters, impact speeds and impact angles on a porous building material surface (ceramic brick). The measurements showed that large drops with high impact speeds splash, and that drops with high impact speeds and small impact angles bounce. The measurements, furthermore, allowed measuring the maximum spreading length and width of the drops as a function of drop diameter, impact speed and impact angle. Then, a numerical analysis was performed to study the distribution of impact speed and angle for raindrops hitting the facade of a 4×4×10 m3 tower building. The results demonstrated typical and important tendencies of impact angle and speed across the facade. Finally, the experimental and numerical data were used in a more precise three-dimensional simulation of impact, absorption and evaporation of random and discrete wind-driven raindrops. This was compared with the common one-dimensional simulation of absorption and evaporation at the facade considering a continuous uniform rain load as boundary condition, and significant differences between the two approaches were observed.status: publishe

Wind-driven rain impact on historical brick wall buildings

An onset is given to whole building modelling for investigating the impact of wind-driven rain (WDR) on the hygrothermal response, indoor climate and mould growth at interior wall surfaces of historical brick wall buildings. First the WDR load on the facades of a 4×4×10 m3 tower is numerically determined. Then the hygrothermal behaviour of the brick wall is numerically analysed on a horizontal slice through the tower. The simulations demonstrate that the impact of WDR loads on the moisture contents in the walls is much larger near the edges of the walls than at the centre. For the case analysed, the absorption and transmission of WDR forms an important moisture source for the indoor environment, and may cause increases of indoor relative humidity in summer and winter, which can reach up to 55 % in winter. The increased thermal conductivity and latent heat effects due to WDR loads yield an increase of 18.7 % in total heating energy consumption in winter; while a much smaller impact on indoor humidity and a very small impact on energy consumption are seen in spring and autumn. Finally, the obtained relative humidity and temperature at the interior wall surfaces are combined with isopleths of generalised spore germination time of fungus mould. The comparison of the results with the WDR load to those without WDR shows significant WDR impacts on mould growth in summer and winter and much smaller impacts in spring and autumn. The results also explain that WDR impacts on mould growth are more pronounced at the edges of the walls than at the centres.Presenters: name: Masaru Abuku affiliation: (Laboratory of Building Physics, Department of Civil Engineering, K.U.Leuven) email: [email protected]

Measurement of strain field in porous materials using X-ray CT and analysis of heat & moisture transfer, stress and strain

凍結融解などにより劣化する多孔質な建築材料の耐久性を予測・評価するため、材料内部の熱＆水分移動と変形を連成する数値解析を行った。数値解析では、ポロメカニクス理論に基づく有限要素解析を行う解析ソルバーの作成を行った。次に、汎用有限要素モデリング・ソフトウエアと解析ソルバーの連携を可能にする有用なツールを開発した。最後に、数値解析結果を検証するための実験室実験を行った。実験では、X線CTにより材料内部の3次元構造とその歪の分布を明らかにした。We conducted numerical analyses in which heat & moisture transfer and deformation in porous materials are simultaneously simulated, in order to predict and evaluate the durability of porous building materials suffering from deterioration due to freeze-thaw and so on. For this purpose, an analysis solver was developed based on poromechanics and a finite element analysis. Next, a useful tool was developed to enable linkage between a generic finite element modelling software and the analysis solver. Finally, we conducted laboratory experiments to verify results of numerical analyses. In the experiments, we clarified the three-dimensional structure of the material and the strain field in the material.研究分野：建築環境工学・建築物