# Study of the Hydrothermal Behavior of Wood Fiber Insulation Subjected to Non-Isothermal Loading
## 1 Introduction  
The construction sector represents a considerable source of energy saving and greenhouse gas reduction [1]. Thermal regulation is constantly evolving and increasingly reduces energy consumption [2]. Therefore, a type of building is emerging characterized by strong thermal insulation intended to limit losses through the envelope. Under these conditions, large heat fluxes by conduction are considerably reduced but it is no longer possible, to neglect latent effects, especially for strongly hygroscopic materials. Furthermore, we are witnessing renewed interest in low-energy impact materials and especially for plant-based materials such as wood and its derivatives whose strongly hygroscopic nature is known. This interest can also be explained by the moisture buffer effect of this type of material on the hygrothermal behavior of buildings [3; 4; 5]. The literature includes several analyses of the behavior of plant-based materials, assemblies, and structures which propose experimental data to validate numerical models of Heat, Air and Moisture (HAM) transfer. [PERSON] et al. [6] studied the response of several assemblies composed of wood wool cement board. Experimental results focused on water content discussion. They showed that the theoryof [PERSON] [7] gave satisfactory results for simulating wetting-drying. [PERSON] et al. [8; 9] presented a very complete study on a dataset for benchmarking 1D transient heat and moisture transfer models of spruce plywood and cellulose insulation in two parts. The first presented their experimental setup and its calibration, while the second presented experimental, numerical, and analytical results that could be used for benchmarking. [PERSON] et al. [10] focused on wood-frame wall assemblies wetted by simulated wind-driven rain infiltration. The analysis mainly dealt with the distribution of water content in the wood during drying. [PERSON] et al. [11] presented extensive data from a laboratory experimental program in which full-scale wall panels were used for model validation. The latter focused only on water content in a 2D configuration. [PERSON] et al. [12] developed an experimental wooden frame house to provide data for the validation of numerical models for whole building heat, air, and moisture transport. They highlighted the importance of temperature-driven moisture diffusion in the case of exterior hygroscopic paneling. [PERSON] et al. [13] presented experimental data on heat, air, and moisture transfer through a full-scale lightweight building envelope wall under real atmospheric boundary conditions. It was found that if the walls were sufficiently airtight the amount of accumulated moisture in the winter season was limited and dried out in the summer for the given configuration. For the same wall type, [PERSON] et al. [14] performed experimental and numerical study to analyse the hygrothermal consequences of using an exterior air barrier. They highlighted buoyancy effects for high walls (above 2 m). [PERSON] et al. [15] presented a dataset for validating 1D heat and mass transfer models within building walls with hygroscopic materials. They showed that moisture accumulation was observed in the layer close to the plaster for the wall without Oriented Strand Board (OSB). [PERSON] et al. [16] carried out an in situ experiment on a full-scale timber frame test building to study the hygrothermal performance of wood-hemp composite insulation in timber frame wall panels with and without a vapor barrier. They observed a very low impact on the U-value for the stresses studied. In the present article, in addition to study the evolution of the water content in a strongly hygroscopic material and proposing data to validate transfer models, we propose a detailed analysis of latent effects in a wood fiber insulation material subjected to non-isothermal conditions under a vapor concentration gradient through experiments and numerical modeling.