InterPore2026

Characterization of hygro-thermal properties of straw bio-based insulation for building application.

19 May 2026, 09:50

1h 30m

Poster Presentation (MS16) Complex fluid and Fluid-Solid-Thermal coupled process in porous media: Modeling and Experiment Poster

Speaker

Arthur Levy (Nantes Université)

Description

Wheat straw is more and more used as insulation and semi-structural material for construction. One classical building method consists in filling a wooden structural frame with compressed straw bales. The crucial issue in such bio-based frames is water. Indeed water condensation in the liquid state would result in rapid rotting and degradation of the insulation. Thus controlling heat and moisture transport through the straw is a priority.
Existing coupled models such as the Kunzel model enable prediction of temperature and water content fields through the wall [Kunzel 95, Claude et al. 23]. They require characterization of hydro-thermal properties of the constituents [Reuge et al. 21].
Nonetheless, due to manual compression of straw bales inside the frames, especially in the case of self-construction, a wide variation in the compression state is observed in the final wall. This highly influences heat and moisture transport properties [Lebed & Augaitis 2017].
In this work a characterization of the thermal conductivity and hydric diffusivity of a local straw bale is conducted. First we focused on thermal and compaction properties. A steady-state hot plate apparatus is used under compression in a mechanical testing machine (100 kN Zwick Roell tensile machine). Because of the large representative volume element of the straw bale structure (several centimeters), the platens are 270x270 mm2.
The obtained compaction behavior is analyzed in the three directions and compared to existing models [Toll and Manson 1995]. Finally the effect of compaction on the anisotropic conductivity is analyzed and compared to existing phenomenological or homogenization theories [Futschik and Witte 1994, Batty et al. 1981, Gaunand et al 25].

references
- Batty, W. J., O'Callaghan, P. W., & Probert, S. D. (1981). Apparent thermal conductivity of glass-fibre insulant: effects of compression and moisture content. Applied Energy, 9(1), 55–76.
- Claude, V., Nguyen, E., Delhaye, A., Mayeux, A., & Charron, S. (2023). Hygroscopic and Thermal Inertia Impact of Biobased Insulation in a Wood Frame Wall. In ICBBM 2023 (Vol. 45, pp. 355–372).
- Futschik, M. W., & Witte, L. C. (1994). Effective thermal conductivity of fibrous materials. American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD (Vol. 271).
- Künzel, H. M. (1995). Simultaneous Heat and Moisture Transport in Building Components One- and two-dimensional calculation using simple parameters . Physics (Vol. 1995).
- Lebed, A., & Augaitis, N. (2017). Research of Physical Properties of Straw for Building Panels. International Journal of Engineering Science Invention, 6(5), 9–14.
- Reuge, N., Collet, F., Pretot, S., Moissette, S., Bart, M., & Lanos, C. (2021). Kinetics of sorption in bio-based materials: Theory and simulation of a demonstrator wall. Proceedings of Institution of Civil Engineers: Construction Materials, 174(3), 129–139.
- Toll, S., & Manson, J.-A. E. (1995). Elastic Compression of a Fiber Network. Journal of Applied Mechanics, 62(1), 223–226.
- Clémence GAUNAND, Yannick DE WILDE, Valentina KRACHMALNICOFF, Adrien FRANCOIS, Veneta GRIGOROVA-MOUTIERS, and Karl JOULAIN. Quantification de l’impact de la résistance thermique de contact entre fibres sur la conduction dans les matériaux d’isolation fibreux. Congrès de la société française de thermique, 2025