Chadi Maalouf

Study of moisture transfer in a double-layered wall with imperfect thermal and hydraulic contact resistances

The objective of this work is to study the effect of taking into account interface contact resistance on the prediction of moisture distribution through multilayered building envelope. Therefore, two mathematical models to describe coupled heat and mass transfer in double-layered porous materials have been investigated: one that considers imperfect contact between layers and another that ignores this phenomenon. Both models are one-dimensional and were implemented using finite difference technique with an implicit scheme. Numerical results are presented in terms of moisture distribution for a double-layered wall and compared with the experimental data available in the current literature. The comparison has shown that the model that disregards interface contact resistance between layers cannot predict correctly one-dimensional heat and moisture transfer within double-layered porous materials. The sensitivity analysis of the simulation parameters and the impact of contact resistances at the whole building level are presented in detail and their effect on the whole building level was analysed. Our results suggest that the thermal contact resistance is the most influent parameter on the moisture flux across the hydraulic contact interface. On the whole building level, simulations indicate that taking into account contact resistances had a slight effect on the indoor relative humidity but a noticeable effect on heating input energy. A decrease of 10% in energy consumption is obtained when contact resistances are considered.

Development and performance evaluation of a hemp–starch composite

This article describes the results of a research project carried out at the University of Reims Champagne-Ardenne. The aim of this article is to develop a new insulating material produced by bonding hemp shives with wheat starch as a binder and to characterize its physical properties such as sorption isotherm, water vapour permeability, thermal conductivity, heat capacity and porosity. The equations of coupled heat and moisture transfer within the panels are introduced. These governing equations are applied on the room level in order to assess the hygrothermal behaviour of the panels and its impact on energy consumption and indoor comfort. Simulations are performed for Nancy (France) winter conditions with the simulation environment Simulation Problem Analysis and Research Kernel (SPARK) suited for complex problems.

Impact of combined moisture buffering capacity of a hemp concrete building envelope and interior objects on the hygrothermal performance in a room

In this article, a hygrothermal building model, taking into account the building envelope, indoor heat and moisture sources, indoor environment and moisture buffering capacity of interior objects, is presented and validated with the test cases found in the literature. The model is used to study the impact of hemp concrete and the moisture buffer capacity of the interior elements on the prediction of the hygrothermal comfort in the building. The numerical results show that the use of hemp concrete in buildings can ensure good hygrothermal comfort. Besides, taking into account the effect of moisture buffering of indoor objects increases the building performance. Our results also suggest that neglecting moisture transfer through the envelope increases significantly the predicted percentage of dissatisfied indices and reduces the acceptability of indoor air quality during the occupied period. This study also confirmed that the combined relative humidity-sensitive ventilation system and moisture buffering capacity of building envelope and of interior objects is a very efficient way to reduce the heating energy consumption.

Mechanical and hygrothermal characterisation of cork concrete composite: experimental and modelling study

Abstract The paper aims to present a new insulating material based on cork aggregates and cement designed for building applications. Samples are prepared by mixing natural cork aggregates, sand, cement and water. Four cork volume dosages are considered, 0, 25, 50 and 75% (relative to the sand). Samples are characterised in terms of hardened density, compressive and flexural strength, as well as thermal conductivity and hydric properties (moisture content, vapour permeability, moisture buffering value and absorption by partial immersion). Results show that increasing cork granule amount tends to increase moisture retention and buffering value but decreases density, thermal conductivity and mechanical properties. Depending on the cork content, cork concrete mixture can be used as thermal insulator or as a structural component.

Bio-based and recycled-waste materials in buildings: A study of energy performance of hemp-lime concrete and recycled-polyethylene terephthalate façades for office facilities in France and Italy

Global environmental issues are arising over the developed and developing world. Improving energy efficiency and reducing Green Gases emissions become the key issues in all the economic sectors and, in particular, the building sector that is one of the most energy-consuming. It is, therefore, important to find alternative building materials with low-environmental impact contributing to global sustainability. In that context, this study reports on the performance of sustainable materials produced from natural resources as hemp-concrete or from recycled-waste nonbiodegradable materials including recycled polyethylene terephthalate. Three façades employing three different materials (hemp-concrete, hemp-concrete with brick and recycled polyethylene terephthalate) were investigated in three cities in France (Nancy and Carpentras) and Italy (Perugia) with different climate. The energy performance of each façade was assessed in terms of cooling and heating demands, electrical consumption for a constant flow rate ventilation mode, considering different orientations. The study also shows the effect of window size (10%, 25%, and 40%) on the annual energy consumption.

Hygrothermal performance of various Typha–clay composite:

This article deals with the influence of both morphology and amount of Typha on hygrothermal behavior of a Typha–clay composite for building application. An agromaterial containing the fiber mix of Typha Australis and clay was made in three samples: three fiber mixtures were prepared with different amounts Typha and cut type (transversal or longitudinal). The physical properties of these materials were studied in terms of porosity, apparent and absolute density, thermal conductivity, and hygric properties. Results show a real impact of the Typha fraction type and its volume content on hygrothermal properties of the studied material due to the porosity. The transversal fraction of Typha (80% in volume weight) seems to be the optimal composition for a better hygrothermal behavior.

Hygrothermal and Acoustical Performance of Starch-Beet Pulp Composites for Building Thermal Insulation

This article deals with the elaboration and the characterization of an innovative 100% plant-based green composite made solely of beet pulp (BP) and potato starch (S). Using this type of material in insulation applications seems a good solution to reduce the CO2 gas emissions in building. The influence of the starch amount on composite characteristics was studied. Four mixtures were considered with different S/BP mass ratios (0.1, 0.2, 0.3 and 0.4). The physical properties of these materials were studied in terms of porosity, apparent and absolute densities, thermal conductivity, and hygric properties. The influence of humidity content on acoustical properties was studied as a function of frequency. Test results show a real impact of both starch and humidity contents on the hygrothermal and acoustical properties of the studied material due to the porosity. The composite with the lowest amount of starch (S/BP = 0.1) seems to be the optimal composition in terms of the hygrothermal and acoustical behaviors.