scholarly journals Damage risk assessment of building materials with moisture hysteresis

2021 ◽  
Vol 2069 (1) ◽  
pp. 012043
Author(s):  
Michele Libralato ◽  
Alessandra De Angelis ◽  
Paola D’Agaro ◽  
Giovanni Cortella ◽  
Menghao Qin ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Building Materials ◽  
Moisture Transfer ◽  
Lower Boundary ◽  
Wood Decay ◽  
Simplified Models ◽  
Desorption Curve ◽  
Decay Risk ◽  
Adsorption Curve

Abstract Heat and Moisture Transfer (HMT) simulations are used to evaluate moisture related damage risks in building envelopes. HMT simulations are commonly performed accepting the hypothesis of not considering the moisture hysteresis of materials. The results of HMT simulation of a timber wall with hysteresis are presented, and compared to the results of three simplified models, showing the effects of hysteresis on the simulation results and on the assessment of the risk of decay. Moisture content is the most influenced variable, while temperature and relative humidity are slightly affected. The wood decay risk analysis is performed using the simplified 20% moisture content rule. Similar temperature values and relative humidity values are calculated as simplified models, while the moisture content annual average values have differences up to 2.3%. The wood decay risk obtained with the simplified models could be overestimated if the simulation is performed using the desorption curve, while it could be underestimated with the adsorption curve. The best approximation is obtained with the mean sorption curve, while the desorption curve and the adsorption curve could be used to calculate the upper and lower boundary of the moisture contents respectively.

scholarly journals Measurements behind Internal Insulation on Solid Masonry Walls with Different Orientations and Degrees of Repair in a Danish Multi-story Building

2020 ◽  
Vol 172 ◽  
pp. 01008
Author(s):  
Lies Vanhoutteghem ◽  
Britt Haker Høegh ◽  
Thor Hansen
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Energy Use ◽  
Wood Decay ◽  
Large Temperature ◽  
Mould Growth ◽  
Insulation System ◽  
Measurement Results ◽  
Heritage Buildings ◽  
Story Building

Internal insulation is used in many heritage buildings to ensure a better indoor environment and reduce energy use. This article describes measurement results from installing an internal insulation system in a Danish multi-story building. The internal insulation system consists of a fully glued vapour tight insulated plasterboard. To reduce the risk for wood decay and mould growth at the wooden beam ends in the floor construction, a 100-200 mm uninsulated gap was left above and below the floor construction. Measurements include the effect of orientation, degree of façade repair and influence of indoor moisture content. Results show in general acceptable hygrothermal conditions behind the insulation system. However, a gradual increase in relative humidity at sun-exposed walls was registered due to ‘summer condensation’. The degree of surface repair also showed an influence on relative humidity levels during this period. At the uninsulated gap above the floor, a higher moisture content indoor resulted in a higher relative humidity, though without exceeding the threshold for mould growth. However, a large temperature range was registered. The influence of the uninsulated gap on reducing the risk of wood decay and mould growth at the beam ends could therefore not unambiguously be confirmed.

scholarly journals Numerical modelling and experimental study of heat and moisture properties of a wall based on date palm fibers concrete

2019 ◽  
Vol 85 ◽  
pp. 02009 ◽  
Author(s):  
Tarek Alioua ◽  
Boudjemaa Agoudjil ◽  
Abderrahim Boudenne
Keyword(s):  
Relative Humidity ◽  
Building Materials ◽  
Moisture Transfer ◽  
Natural Fibers ◽  
Good Prediction ◽  
The Finite Element Method ◽  
Hygrothermal Behavior ◽  
Date Palm Fibers ◽  
Different Depths ◽  
Heat And Moisture

In the present paper, we study with both experimental and numerical aspect the heat and moisture transfer properties of a wall based on concrete filled with the natural fibers. The wall was placed in climatic chamber and temperature and relative humidity were monitored at different depths. A developed model describing heat and moisture transfers in porous building materials was implemented in COMSOL Multiphysics and solved with the finite element method. The obtained results are compared with experimental data. A relatively good agreement was obtained for both temperature and relative humidity variation at different depths. Finally, the developed model gives almost a good prediction despite the classical difficulties encountered at the experiment, which is very promising for the prediction of the hygrothermal behavior of bio-based building materials at different conditions.

scholarly journals Modeling of Coupled Heat and Mass Transfers in a Stabilized Earthen Building Envelope with Thatched Fibers

Fibers ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 75
Author(s):  
Madeleine Nitcheu ◽  
Donatien Njomo ◽  
Pierre Meukam ◽  
Cyrille Fotsing Talla
Keyword(s):  
Moisture Content ◽  
Building Materials ◽  
Numerical Solutions ◽  
Moisture Transfer ◽  
Building Envelope ◽  
One Dimensional ◽  
Composites Materials ◽  
Model Equations ◽  
Mass Transfers ◽  
Heat And Moisture

In order to reduce the heat and mass transfers in buildings, which increase energy bills, the development of composites materials such as earth bricks stabilized with thatch fibers is important for their construction. This paper aims to study a one-dimensional model of heat and moisture transfer through porous building materials. The coupled phenomena of heat and mass transfer are described by the Luikov model. Equations and boundary conditions are discretized using the finite difference method. The results obtained illustrate the temporal evolutions of the temperature and the moisture content, as well as the distributions of the temperature and moisture content inside the wall. The profile of the temperature and water content that are obtained are compared with the other numerical solutions that are available in the literature.

scholarly journals Suitability of time domain reflectometry (TDR) for moisture content monitoring in historic building walls

2019 ◽  
Vol 282 ◽  
pp. 02051
Author(s):  
Teresa Stingl Freitas ◽  
Ana Sofia Guimarães ◽  
Vasco Peixoto de Freitas
Keyword(s):  
Moisture Content ◽  
Wall Thickness ◽  
Building Materials ◽  
Moisture Transfer ◽  
Correct Diagnosis ◽  
Time Domain Reflectometry ◽  
Efficiency Evaluation ◽  
Historical Buildings ◽  
Intervention Measures ◽  
Building Walls

Measuring moisture content in building materials is crucial for the correct diagnosis of buildings pathologies, for the adoption of appropriate intervention measures and for the efficiency evaluation of the treatment solutions applied. There are several different techniques available to measure and monitoring the moisture content in building materials. However, it still remains a great challenge to perform those studies in historical buildings, since minor-destructive techniques are required. Furthermore, if continuous moisture content readings in space are desired, in order to study the moisture transfer phenomenon along the wall thickness, the challenge is even greater. The TDR technique is a relatively new method for measurement of moisture content in building materials with a set of unexplored potentialities capable of satisfying the two mentioned requirements. In this paper, the suitability of the TDR technique to obtain continuous cross-section moisture content profiles has started to be tested on two limestone prototype walls. Each wall was equipped with four TDR probes, designed practically with the same length of the wall thickness and placed at different heights. All the necessary equipment, installation steps, and difficulties are here presented. The preliminary results suggest that the TDR technique is suitable for moisture content monitoring in consolidated porous building materials.

scholarly journals Experimental evaluation of the effect of different design conditions on the risk of decay in solid wood exposed to outdoor climate

2021 ◽  
Vol 71 (342) ◽  
pp. e247
Author(s):  
M. Conde-García ◽  
M. Conde-García ◽  
J.A. Tenorio-Ríos ◽  
J. Fernández-Golfín
Keyword(s):  
Moisture Content ◽  
Structural Design ◽  
Wood Decay ◽  
Solid Wood ◽  
Structural Elements ◽  
Wood Moisture ◽  
Outdoor Climate ◽  
Decay Risk ◽  
Excessive Accumulation ◽  
Horizontal Arrangement

Wood decay have the greatest impact on in-service wood structural elements. In most cases, decay is associated with excessive accumulation of moisture in the wood. The structural design conditions have an effect on the wood moisture content and this affects the service life of the material. In this study, which involved an experimental trial specifically designed to embrace different structural design conditions, the moisture content evolution in different places affected by different design conditions was evaluated over a period of three years in Madrid (Spain). The effect of protection by eaves, separation from the ground and the vertical or horizontal arrangement of the wood elements on the monthly evolution of the moisture content and decay risk are assessed.

scholarly journals Study of the Equilibrium Sorption Humidity of the Materials of the Enclosing Constructions of Buildings at a Temperature -20 °C

2018 ◽  
pp. 149-154
Author(s):  
Igor Y. Kiselev
Keyword(s):  
Relative Humidity ◽  
Building Materials ◽  
Moisture Transfer ◽  
Lightweight Concrete ◽  
Sharp Decrease ◽  
Equilibrium Sorption ◽  
Adsorbed Monolayer ◽  
Condensed Water ◽  
Heat And Moisture ◽  
Internal Pore

Equilibrium sorption humidity (further: sorption humidity) together with the thermal conductivity is the most important thermo-technical property of building materials, since itlargely determines the course of the process of heat- and moisture transfer through the enclosing constructions of buildings and, consequently, also the thermo-technical properties of these constructions. The isotherms of the absorption of vapors of water for foam concrete, cellular concrete, expanded-clay lightweight concrete, expanded-clay-pearlite lightweight concrete, expanded-shungizitlightweight concrete and arbolit were experimentally (by exiccator method) determined at temperatures -20, -10,4, +1,2, +20 and +35 °С. The analysis of the obtained results showed that the sorption humidity of all investigated materials increases with the temperature decrease from +35 °C to -10,4 °C. However, at a temperature -20 °С sorption humidity decreases, and what is more, that, it becomesless than the sorption humidity of these materials at a temperature of +20 °С. The reasons for the decrease of the sorption humidity of building materials at a temperature -20 °С in comparison with the values of this property at a temperature of +20 °C appears: with the relative humidity of air φ< 80%: the sharp decrease of the mobility of water molecules of the first adsorbed monolayer at a certain temperature, which belongs to temperature range from -10,4 to -20 °С, and, as a result, a sharp increase of thelifetime of a water molecule in the first adsorbed monolayer; with the relative humidity of air φ> 80% appears the second reason for the decrease of the equilibrium sorption humidity of building materials at a temperature -20 °C, namely, the freezing of some share of the capillary-condensed water and blocking by formed fixed ice the access of water vapor into the internal pore volume of material.

CATFISH DRYING (Clarias Batraclus) USING ‘TEKO BERSAYAP’ SOLAR DRYER

2012 ◽  
Vol 2 (1) ◽  
pp. 14-20
Author(s):  
Yuwana Yuwana
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Ambient Temperature ◽  
Drying Rate ◽  
Drying Process ◽  
Drying Time ◽  
Ambient Relative Humidity ◽  
Solar Dryer

Experiment on catfish drying employing ‘Teko Bersayap’ solar dryer was conducted. The result of the experiment indicated that the dryer was able to increase ambient temperature up to 44% and decrease ambient relative humidity up to 103%. Fish drying process followed equations : KAu = 74,94 e-0,03t for unsplitted fish and KAb = 79,25 e-0,09t for splitted fish, where KAu = moisture content of unsplitted fish (%), KAb = moisture content of splitted fish (%), t = drying time. Drying of unsplitted fish finished in 43.995 hours while drying of split fish completed in 15.29 hours. Splitting the fish increased 2,877 times drying rate.

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