Comparison of Numerical HMT Codes to Simulate MBV Test of Hemp-Earth Composites

2022 ◽  
Author(s):  
Sana Khaled ◽  
Marjorie Bart ◽  
Sophie Moissette ◽  
Florence Collet ◽  
Sylvie Prétot ◽  
...  
Keyword(s):  
Indoor Air ◽  
Building Materials ◽  
Numerical Study ◽  
Water Vapor Permeability ◽  
Building Envelope ◽  
Vapor Permeability ◽  
Building Envelopes ◽  
Classical Models ◽  
Points Of View ◽  
Adsorption Curve

Bio-based and earth materials are growingly used for the building envelopes because of their numerous benefits such as slight environmental impact, great hygrothermal performances, effective regulation of the perceived indoor air quality and human comfort. In such materials, the phenomenon of mass transfer is complex and has a great impact on the performance of building envelope. Therefore, it is important to identify and understand the hygrothermal phenomena to be able to simulate accurately the envelope behavior. Nevertheless, the classical models that depict hygric transport within building materials seem not accurate enough for bio-based materials as they are simplified on several points of view. The correlation that exists between water content and relative humidity is mostly simplified and is modeled by a single curve, the hygric storage capacity is often overstated and the hysteresis is neglected. This paper deals with numerical study of hygric transfer within hemp-earth building material by using WUFI® Pro 6.5, a commercial software, and TMC code developed at the LGCGM (Moissette and Bart, 2009) . This code was validated regarding EN 15026 standard (Moissette and Bart, 2009) and has evolved over the years by integrating the hysteresis phenomena (Aït-Oumeziane et al., 2015). Thus, a significant enhancement of the numerical simulations on desorption phase was shown. This study investigates the simulation of MBV test performed on a hemp-earth material for which only the adsorption curve is known as input. Missing parameters (water vapor permeability and desorption curve) are fitted considering the first cycle of MBV test with TMC code. Then, MBV test is simulated with WUFI® Pro 6.5 and TMC code without and with hysteresis. The results highlight the need to include hysteresis to accurately simulate dynamic hygric phenomena, and show that it is possible to find missing parameters by fitting dynamic solicitations.

scholarly journals Hygrothermal Behavior of Earth-Based Materials: Experimental and Numerical Analysis

2020 ◽  
Vol 330 ◽  
pp. 01030
Author(s):  
Meriem Saidi ◽  
Amel Soukaina Cherif ◽  
Ezeddine Sediki ◽  
Belkacem Zeghmati
Keyword(s):  
Building Materials ◽  
Moisture Transfer ◽  
Transfer Problem ◽  
Numerical Study ◽  
Water Vapor Permeability ◽  
Average Moisture Content ◽  
Vapor Permeability ◽  
Hygrothermal Behavior ◽  
Coupled Heat And Moisture ◽  
Building Walls

Bio-based building materials such as earth bricks are attracting renewed interest throughout the world due to their thermal and environmental properties. In this work, a numerical study of the hygrothermal behavior of building walls consist of compressed earth bricks (CEB) and stabilized earth bricks (SEB) was performed. A two-dimensional Luikov model for evaluating the temperature and the moisture migration in porous building materials was proposed. The coupled heat and moisture transfer problem was modeled. The governing equations of a mathematical model were solved numerically with the finite difference method. Input parameters in the model and their dependency on stabilizers content were determined by laboratory experiments. In order to specify the effect of chemical stabilization on the heat and mass transfer within studied materials, average moisture content and temperature were presented as a function of time. Results show that the addition of chemical stabilizers enhances the heat transfer through the earthen materials and reduces their water vapor permeability.

Air infiltration through building envelopes: A review

2011 ◽  
Vol 35 (3) ◽  
pp. 267-302 ◽  
Author(s):  
Chadi Younes ◽  
Caesar Abi Shdid ◽  
Girma Bitsuamlak
Keyword(s):  
Indoor Air ◽  
Energy Demand ◽  
Building Energy ◽  
Building Envelope ◽  
Energy Costs ◽  
Air Leakage ◽  
Building Envelopes ◽  
Air Infiltration ◽  
Considerable Impact ◽  
Evaluation Techniques

Air leakage through the building envelope into the building interiors has a considerable impact on the energy loads and consequently energy demand and energy costs of buildings. This phenomenon known as infiltration happens through various openings and venues in the building envelope varying from large openings such as doors and windows to minute cracks and crevices. In addition to impacting building energy loads, infiltration impacts indoor air quality and can result in moisture accumulation problems in the building envelope. A generalized review of infiltration that includes evaluation techniques and models, quantification, and interaction with other heat transfer phenomena is presented in this article.

Structure and Properties of Total-Heat Exchange Membranes for Energy Saving Heat Exchange Ventilation Processes

2011 ◽  
Vol 374-377 ◽  
pp. 568-571 ◽  
Author(s):  
Li Xin Xue ◽  
Bing Xin Liu ◽  
Jing Chen ◽  
An Chun Shao
Keyword(s):  
Heat Exchange ◽  
Air Quality ◽  
Energy Saving ◽  
Indoor Air ◽  
Water Vapor Permeability ◽  
Functional Materials ◽  
Casting Process ◽  
Total Heat ◽  
Vapor Permeability ◽  
Structure And Properties

As complement to air conditioners, ventilation systems are playing important roles in keeping human health as well as saving energy. They improved indoor air quality by replacing inside polluted air with outside fresh air. To reduce the energy needed to condition the induced fresh air, heat exchanging processes are designed to reduce the temperature differences between this fresh air and the indoor air. Heat exchanging processes using total heat exchange membranes (THEM) allowed not only the exchange of heat but also humidity, generally providing better energy saving and air quality improvement results. Recently, we have studied a novel class of THEM made from a casting process using inorganic and organic functional materials. Their structure and properties characterized with Scanning Electron Microscopy (SEM), BET Adsorption test, Water-vapor Permeability Analysis, CO2 Permeation Test, and Heat Exchange Efficiency Test are discussed here.

scholarly journals Evaluation Model of Environmental Impacts of Insulation Building Envelopes

2020 ◽  
Vol 12 (6) ◽  
pp. 2258
Author(s):  
Qianmiao Yang ◽  
Liyao Kong ◽  
Hui Tong ◽  
Xiaolin Wang
Keyword(s):  
Life Cycle ◽  
Environmental Impact ◽  
Environmental Impacts ◽  
Environmental Performance ◽  
Building Materials ◽  
Energy Savings ◽  
Building Envelope ◽  
Building Envelopes ◽  
Entire Life ◽  
Entire Life Cycle

Energy consumption during use is the focus of insulation envelope design, but the environmental impact of other stages in the entire life cycle of building envelopes should be of equal concern. In this paper, a model has been developed based on the life-cycle environmental assessment for calculating the environmental impacts of building envelopes. The model proposed will be useful to evaluate the environmental performance of various envelopes to optimize the design of energy-saving envelopes. Consequently, lots of experiments are conducted for environmental impact assessment and analysis for external windows and filler walls with energy-savings in heating areas of China. Four conclusions can be drawn from the analysis. (1) K of building envelope is the design parameter of the greatest impact on environmental performance and has a critical value, which is the value that has the smallest environmental impact over the entire life cycle. (2) The importance of the environmental impact of the building envelope during the life cycle stages is as follows: usage > production > transportation > disposal > construction. The construction process of the thermal insulation wall could be negligible. (3) The choice of regional building materials should consider the distance of transportation, which may be the key factor determining its life cycle environmental performance. (4) Aerated concrete EPS walls and wooden windows are the first choices for envelope construction from the environmental impact throughout the life cycle.

Correlation of Water Vapor Permeability with Microstructure Characteristics of Building Materials Using Robust Chemometrics

2013 ◽  
Vol 99 (2) ◽  
pp. 273-295 ◽  
Author(s):  
Timokleia Togkalidou ◽  
Maria Karoglou ◽  
Asterios Bakolas ◽  
Anastasia Giakoumaki ◽  
Antonia Moropoulou
Keyword(s):  
Water Vapor ◽  
Building Materials ◽  
Water Vapor Permeability ◽  
Vapor Permeability ◽  
Microstructure Characteristics

scholarly journals An Innovative Method for the Recycling of Waste Carbohydrate-Based Flours

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1414
Author(s):  
Carola Esposito Corcione ◽  
Raffaella Striani ◽  
Francesca Ferrari ◽  
Paolo Visconti ◽  
Daniela Rizzo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Solubility ◽  
Water Vapor Permeability ◽  
Accelerated Ageing ◽  
Vapor Permeability ◽  
The Novel ◽  
Maize Starch ◽  
Points Of View ◽  
First Time

This work represents an innovative study that, for the first time, explores the possibility to use waste flours to produce thermoplastic polymeric bio-films. To the best of our knowledge, this is the first time that waste flours, derived from bakeries, pizzerias or pasta factories, have been proposed for the production of bio-polymers, as a replacement of neat starch. To this aim, durum waste flour derived from a pasta factory, soft waste flour derived from pizzerias and neat maize starch used as control material were firstly analyzed from dimensional, morphological and chemical points of view. Afterwards, waste flour films were produced by the addition of a nature-based plasticizer, glycerol. Mechanical characterization of the plasticized thermoplastic films, produced by compression molding, evidenced low performances, even in the case of the neat maize starch. In order to improve the mechanical properties, the possibility to include polylactic acid and cardanol-based plasticizer was also investigated. Mass transport properties of all the produced bio-films were investigated by measuring their water vapor permeability and hygroscopic absorption. The durability properties of the bio-films were assessed by accelerated ageing tests, while the bio-degradability of the waste-based films was evaluated by measuring the solubility and the degradation in water. The physicochemical analyses of the novel bio-films evidenced good mechanical properties; specifically, the waste-based films showed a lower hygroscopic absorption and water solubility than those of the blends containing neat starch.

Evaluation of a Marine Dredged Sediment as Raw Material Compared to Volcanic Scoria for the Development of Lime-Pozzolan Eco-Binders

2022 ◽  
Author(s):  
Salim KOURTAA ◽  
Morgan Chabannes ◽  
Frederic Becquart ◽  
Nor Edine Abriak
Keyword(s):  
Building Materials ◽  
Ghg Emissions ◽  
Water Vapor Permeability ◽  
Hydrated Lime ◽  
Embodied Energy ◽  
Raw Material ◽  
Strength Development ◽  
Vapor Permeability ◽  
Low Carbon ◽  
Dredged Sediment

In the context of global warming, the built environment offers relevant opportunities to reduce GHG emissions that underlie climate change. In particular, this can be achieved with the development of low-embodied energy building materials such as bio-based concretes. Hemp concrete has been the subject of many investigations in the field of non-load bearing infill walls in France since the early 1990s. In addition to hygrothermal performances, the use of crop by-products definitely helps to limit the carbon footprint. Hemp concretes are often produced by mixing the plant aggregates with lime-based binders. The latter have many benefits among which the water vapor permeability. However, CO2 emissions due to the decarbonation of limestone for the production of lime largely contribute to the overall environmental balance of these materials. The use of natural pozzolans (volcanic scoria) combined with hydrated lime goes back to the Greco-Roman period and reduces carbon emissions. Nonetheless, it does not necessarily meet the issue related to the depletion of granular natural resources. Hence, this study deals with the design of a new low-carbon binder based on marine dredged sediment seen as an alternative strategic granular resource that can be considered renewable. The sediment comes from the Port of Dunkirk in the North of France and is mainly composed of silt and quartz sand. It was finely ground and compared to a lowly reactive basaltic pozzolan. Lime-pozzolan pastes were prepared and stored in a moist environment under room (20°C) and high temperature (50°C). The hardening kinetics of pastes was followed through mineralogical studies (TGA, XRD) and compressive strength development. The results showed that the hardening of pastes including the marine sediment was suitable in the case of samples stored at 50°C and make it possible to use such a binder for precast bio-based concretes.

scholarly journals On the importance of desiccant during the determination of water vapor permeability of permeable insulation material

2020 ◽  
Vol 172 ◽  
pp. 14003
Author(s):  
Thibaut Colinart ◽  
Patrick Glouannec
Keyword(s):  
Water Vapor ◽  
Building Materials ◽  
Wood Fiber ◽  
Construction Materials ◽  
Water Vapor Permeability ◽  
Vapor Permeability ◽  
Diffusion Resistance ◽  
Insulation Material ◽  
The Impact

Water vapor permeability of building materials is usually measured using dry cup test according to the ISO 12572 standard. For this test, suitable adsorbing desiccant should be used to provide stable low vapor pressure conditions within the cup and, thus, to ensure the good accuracy of the measurement. In this work, different adsorbing desiccants mentioned in the ISO 12572 standard are tested for measurements performed on wood fiber insulation. For each experiment, relative humidity is monitored inside the dry cup. The results indicate that 0 %RH is not reached inside the dry cup and boundary condition is not always stable for highly permeable construction materials, depending on the adsorbing desiccants. The impact of these observation is evaluated on the determination of water vapor diffusion resistance factor and compared to other sources of uncertainties.

scholarly journals Multiscale modelling for better hygrothermal prediction of porous building materials

2018 ◽  
Vol 149 ◽  
pp. 02005 ◽  
Author(s):  
Rafik Belarbi ◽  
Fares Bennai ◽  
Mohammed Yacine Ferroukhi ◽  
Chady El Hachem ◽  
Kamilia Abahri
Keyword(s):  
Indoor Air ◽  
Building Materials ◽  
Moisture Transfer ◽  
Building Envelopes ◽  
3D Images ◽  
Porous Building Materials ◽  
Multi Scale ◽  
Scale Modelling ◽  
Physical Phenomena

The aim of this work is to understand the influence of the microstructuralgeometric parameters of porous building materials on the mechanisms of coupled heat, air and moisture transfers, in order to predict behavior of the building to control and improve it in its durability. For this a multi-scale approach is implemented. It consists of mastering the dominant physical phenomena and their interactions on the microscopic scale. Followed by a dual-scale modelling, microscopic-macroscopic, of coupled heat, air and moisture transfers that takes into account the intrinsic properties and microstructural topology of the material using X-ray tomography combined with the correlation of 3D images were undertaken. In fact, the hygromorphicbehavior under hydric solicitations was considered. In this context, a model of coupled heat, air and moisture transfer in porous building materials was developed using the periodic homogenization technique. These informations were subsequently implemented in a dynamic computation simulation that model the hygrothermalbehaviourof material at the scale of the envelopes and indoor air quality of building. Results reveals that is essential to consider the local behaviors of materials, but also to be able to measure and quantify the evolution of its properties on a macroscopic scale from the youngest age of the material. In addition, comparisons between experimental and numerical temperature and relative humidity profilesin multilayers wall and in building envelopes were undertaken. Good agreements were observed.

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