Étude multi-échelle du comportement hygrothermique, environnemental et mécanique des bâtiments en paille

Les matériaux biosourcés, tels que la paille, ont généralement une faible énergie intrinsèque. Ils deviennent donc une alternative prometteuse pour améliorer la performance énergétique des bâtiments et réduire leur empreinte carbone. Comparés aux matériaux de construction courants, les matériaux biosourcés permettraient un meilleur contrôle de la température intérieure et des variations d'humidité relative, améliorant ainsi le confort thermique. Bien que largement étudié, il y a encore un manque de données concernant la performance thermique, hygrique et énergétique de telles structures. L'objectif de cette thèse est d'apporter une partie des réponses à travers des travaux expérimentaux et numériques.Bio-based materials such as straw have generally a low embodied energy. Therefore, they are becoming a promising alternative to improve buildings energy performance and reduce their carbon footprint. When compared to common building construction materials, bio-based materials allegedly provide better control of the indoor temperature and relative humidity variations, thus ameliorating thermal comfort. Although widely studied, there is still a lack of data concerning the thermal, hygric, and energetic performance of such structures. The purpose of this thesis is to provide some of the answers through experimental and numerical work

Étude multi-échelle du comportement hygrothermique, environnemental et mécanique des bâtiments en paille

Bio-based materials such as straw have generally a low embodied energy. Therefore, they are becoming a promising alternative to improve buildings energy performance and reduce their carbon footprint. When compared to common building construction materials, bio-based materials allegedly provide better control of the indoor temperature and relative humidity variations, thus ameliorating thermal comfort. Although widely studied, there is still a lack of data concerning the thermal, hygric, and energetic performance of such structures. The purpose of this thesis is to provide some of the answers through experimental and numerical work.Les matériaux biosourcés, tels que la paille, ont généralement une faible énergie intrinsèque. Ils deviennent donc une alternative prometteuse pour améliorer la performance énergétique des bâtiments et réduire leur empreinte carbone. Comparés aux matériaux de construction courants, les matériaux biosourcés permettraient un meilleur contrôle de la température intérieure et des variations d'humidité relative, améliorant ainsi le confort thermique. Bien que largement étudié, il y a encore un manque de données concernant la performance thermique, hygrique et énergétique de telles structures. L'objectif de cette thèse est d'apporter une partie des réponses à travers des travaux expérimentaux et numériques

Thermal and mechanical behavior of straw-based construction: A review

International audienceBio-based materials such as straw are becoming a promising alternative to improve the building energy performance and to reduce its carbon footprint. When compared to common building construction materials, bio-based materials control the temperature and the relative humidity variation to ameliorate the indoor comfort with a low embodied energy and CO2 emission. This paper presents a comprehensive review of the thermal and mechanical properties of straw-based materials and buildings. The objective is to synthesis the work that has been carried out by the research community and to compare the results. The paper first introduces straw bale as a construction material from a historical viewpoint and in the context of the current building sector. The second part focuses on the available chemical and microstructural data of the straw fiber. The third part refers to the thermophysical and mechanical properties of the bales. The fourth part reviews the numerical and experimental studies done at the wall scale. The fifth part describes straw bale construction methods considering the regulation, structure requirements, and life cycle assessment data. Last, a critical analysis of the currently available data on straw as a building material is carried out and pending research issues are discussed. It was found that, despite abundant literature on structural and thermal properties of straw bale constructions, there is still a lack of some information. At a fiber scale, more research should be done to compare straw fibers to other natural and synthetic fibers. At a bale scale, further pH-related research is needed because it affects the material's interior conditions and durability. In addition, a thermal conductivity model for straw should be developed. On a bigger scale, the hygrothermal characteristics of various types of walls must be measured and computed experimentally and theoretically under various exterior and internal situations. More research is needed to improve the sound resistance of the straw wall by adding new layers capable of absorbing acoustic waves. Studies on the energy behavior, cost analysis, and how interior air moisture is self-regulated in straw buildings are needed at the building size. Therefore, a lack of consistent data among the different studies was noted depending on the straw characteristics

A Mini-Review on Straw Bale Construction

International audienceStraw bale building construction is attracting a revived public interest because of its potential for reduced carbon footprint, hygrothermal comfort, and energy savings at an affordable price. The present paper aims to summarize the current knowledge on straw bale construction, using available data from academic, industry, and public agencies sources. The main findings on straw fibers, bales, walls, and buildings are presented. The literature shows a wide variability of results, which reflects the diversity of straw material and of straw construction techniques. It is found that the effective thermal conductivity, density, specific heat, and elastic modulus of straw bales used in construction are in the range 0.033–0.19 W/(m·K), 80–150 kg/m3, 1075–2000 J/(kg·K), and 150–350 kPa respectively. Most straw-based multilayered walls comply with fire resistance regulations, and their U-value and sound reduction index range from 0.11 to 0.28 W/m2 K and 42 to 53 dB respectively, depending on the wall layout. When compared to standard buildings, straw bale buildings do provide yearly reductions in carbon emissions and energy consumption. The reductions often match those obtained after applying energy-saving technologies in standard buildings. The paper ends by discussing the future research needed to foster the dissemination of straw bale construction

Effective thermal conductivity model of straw bales based on microstructure and hygrothermal characterization

International audienceStraw fibers are natural fibers that have a strong insulating property and a minimal environmental effect, making them suitable construction materials. In the construction sector, to predict the building energy consumption, the thermal conductivity of the materials composing the envelopes must be precisely known, which is not the case for the straw material. The properties of a straw bale are variable and mainly depend on its density, fibers orientation, chemical composition, temperature and relative humidity. Consequently, this study consists of determining a mathematical equation to predict the effective thermal conductivity of straw bales that can be applied to all straw types, in different circumstances. For this purpose, the size, distribution, and morphology of straw fibers are first determined from microscopic images. Second, a mathematical model for estimating the thermal conductivity is suggested using the heat transfer models of porous and fibrous materials. The numerical model is validated by an experimental study that measures the thermal conductivity of straw bales by altering their density between 80 and 120 kg/m3, their relative humidity between 15 % and 95 %, and their temperature between 15 ˚C and 55 ˚C. The experimental results show that the thermal conductivity increases from a minimum of 0.047 W/(m∙K) to a maximum of 0.09 W/(m∙K) when increasing the three altered factors. For a straw fiber having 40% cellulose content, the thermal conductivity increased from a minimum of 0.05 W/(m∙K) to a maximum of 0.0832 W/(m∙K). This behavior is found the same for the numerical findings. The comparison of numerical and experimental values shows a good agreement, with a root mean square error of 0.005 W/(m∙K) and a scatter index of 5.5 %

Hygrothermal performance of multilayer straw walls in different climates

International audienc

Performance hygrothermique des enveloppes multicouches utilisant le matériau paille

National audienc

Advances in solar greenhouse systems for cultivation of agricultural products

International audienc

Performance hygrothermique des enveloppes multicouches utilisant le matériau paille

National audienc