Abstract
Due to the environmental impact of building materials, researches on sustainable materials, such as bio-based and earth materials, are now widespread. These materials offer numerous qualities such as their availability, recyclability and their ability to dampen the indoor relative humidity variations due to their hygroscopicity. As these materials can absorb large amount of humidity, numerical and experimental studies of their hygrothermal behaviour are crucial to assess their durability. To validate a hygrothermal model, numerical and experimental data have to be confronted. Such confrontation must take into consideration the uncertainties related to the experimental protocol, but also to the model. Statistical tools such as uncertainty and global sensitivity analysis are essential for this task. The uncertainty analysis estimates the robustness of the model, while the global sensitivity analysis identifies the most influential input(s) responsible for this robustness. However, these methods are not commonly used because of the complexity of hygrothermal models, and therefore the prohibitive simulation cost. This study presents a methodology for comparing the numerical and experimental data of a rammed earth wall subjected to varying temperature and relative humidity conditions. The main objectives are the investigation of the uncertainties impact, the estimation of the model robustness, and finally the identification of the input(s) responsible for the discrepancies between numerical and experimental data. To do so, a recent and low-cost global variance-based sensitivity method, named RBD-FAST, is applied. First, the uncertainty propagation through the model is calculated, then the sensitivity indices are estimated. They represent the part of the output variability related to each input variability. The output of interest is the vapour pressure in the middle of the wall to confront it to the experimental measurement. Good agreement is obtained between the experimental and numerical results. It is also highlighted that the sorption isotherm is the main factor influencing the vapour pressure in the material.
Highlights
IntroductionIn the context of energy transition, earthen materials offer interesting advantages such as their low embodied energy or their ability to regulate the indoor relative humidity in a passive way, namely their moisture buffering capacity
A large amount of earthen constructions is present worldwide
This study presents a methodology for comparing the numerical and experimental data of a rammed earth wall subjected to varying temperature and relative humidity conditions
Summary
In the context of energy transition, earthen materials offer interesting advantages such as their low embodied energy or their ability to regulate the indoor relative humidity in a passive way, namely their moisture buffering capacity. Some studies focused on measuring the hygrothermal properties of earth. They largely differ from one earth to another due to its variation of composition depending on the soil it was extracted from. A state-ofthe-art on the hygrothermal properties of numerous earth may be found in [1]. It is widely acknowledged that the heterogeneity of structure of this material may lead to large experimental uncertainties, and current standards are not adapted for this material [2]
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