# Impact of Temperature on the Moisture Buffering Performance of Palm and Sunflower Concretes
## 1 Introduction
This is predictable because a porous material has the potential to adsorb or desorb moisture through intra-/inter-pores. Although there is a relationship between porosity and density, the latter property has no correlation with the MBV. An analysis of [PERSON] and [PERSON] [23] showed a correlation coefficient equal to 0.02 between the density and MBV. By deduction, it is possible to discuss the influence of the thickness of the material on the MBV, but the density has no relationship with the MBV, unlike the porosity, which has a very significant relationship. As a result, these scientific studies showed that porous materials allow passive and effective regulation of the indoor relative humidity thanks to their moisture buffer capacity. The addition of fibrous matters from plant or animal origin to building materials has been conducted intuitively since antiquity [28; 29]. However, scientific study of fiber-reinforced concretes made with mineral or synthetic fibers began in the early 20 th century. Recently, in many studies, vegetable and organic fibers were used to substitute mineral or synthetic fibers in order produce bio-based building materials [29; 30; 31]. Bio-based concretes (such as hemp concrete, flax concrete, palm concrete and sunflower concrete) are dedicated to natural construction which is a means of achieving sustainable construction over time. These materials have very high porosity. They are produced by mixing bio-based aggregates, binder (cement, lime, etc.) and water. Bio-based concretes are a good response to limit the impact of buildings on the environment and meet the standards of thermal regulations (for example, RE 2020 in France) thanks to their thermal inertia and insulation which ensure better health of the occupants, thermal comfort and indoor air quality (IAQ) in the habitat [9; 16; 26; 27]. Recently, a study of [PERSON] et al. 2021 [32] showed that the combined dynamic sorption capacity (moisture and pollutant buffering capacity) of bio-based materials such as hemp lime concrete makes it possible to reduce the level of the indoor concentration of pollutants as well as the indoor relative humidity. The MBV is a hygric property, which depends on the relative humidity of the surrounding ambience. Other hygric properties such as the permeability to water vapor (WV), sorption isotherm, penetration depth and mass transport coefficient may be correlated with the MBV. These hygric properties and boundary conditions depend on the relative humidity, which is also dependent on the temperature. Therefore, it should be noted that the temperature is an important factor influencing moisture buffer values. A recent literature review carried out by [PERSON] and [PERSON] [23] and a review conducted by the authors show that, to date, there is a lack of in-depth knowledge on the impact of the ambient temperature on the moisture buffer value of bio-based building materials. To overcome the lack of knowledge in the literature, the aim of this article is to examine the influence of the temperature on the moisture buffer performance of highly hygroscopic bio-based materials focusing on palm concrete (PC) and sunflower concrete (SC). It is aimed to underline that the MBV characterizes the ability of a multilayer material or simple layer to moderate the variation in the indoor relative humidity in buildings. In the literature, the MBV was determined at a constant temperature (e.g., 23 \({}^{\circ}\)C), while, in reality, the indoor temperature in buildings is under variable dynamic conditions. Some experimental studies found in the literature on hygroscopic materials [13; 33; 34] showed that the MBV is influenced by the temperature and the increase in temperature induces an increase in the MBV. For example, MBVs of palm concrete which were measured at 23 \({}^{\circ}\)C and 10 \({}^{\circ}\)C by [PERSON] et al. (2018) [13] were 2.96 and 2.03 g/(m\({}^{2}\)%RH), respectively (with a percentage deviation of 31.42%).