# Impact of Temperature on the Moisture Buffering Performance of Palm and Sunflower Concretes
## 4 Numerical Study and Discussions
### Impact of the Moisture Buffering Capacity on Indoor Relative Humidity of an Office Room
#### 4.2.2 Impact of Moisture Buffering Capacity Classification on Indoor RH  
In this subsection, the impact of the MBV classification proposed in the NordTest project [7] on the indoor relative humidity at the room scale is studied. For this purpose, simulations were carried out by varying the MBV value from 0 to 4 g/(m2%RH), with a step of 0.5. Figure 11 shows the results of the comparative study of the influence of the MBV value on the indoor RH variation. It can be seen that, at the equilibrium state, the indoor RH variation is periodic (according to the occupied period) and the impact of the MBV on the variation in the indoor relative humidity is significant. A higher MBV results in a lower indoor relative variation. Numerically, as it is shown in Figure 11 and Table 5, when the hygric inertia of the walls is neglected (MBV = 0 g/(m2%RH), the case without moisture buffering capacity), the amplitude (A\({}_{\text{MBV=0}}\)) is 23% compared to A\({}_{\text{(MBV=1)}}\) = 15%, A\({}_{\text{(MBV=2)}}\) = 8%, A\({}_{\text{(MBV=3)}}\) = 6% and A\({}_{\text{(MBV=2)}}\) = 5% when the MBVs are equal to: 1, 2, 3 and 4 g/(m2%RH), respectively. These obtained results show that the moisture buffering capacity can reduce the indoor RH variation and needs to be taken into account in building design.  
Figure 11: Indoor RH variation of an office room with different values of MBV.  
Figure 10: Studied configuration of the office room occupied by two persons [32].  
In order to quantify the hygric regulation capacity, we define a coefficient, \(f=\text{A}/\text{A}_{0}\), which represents the ratio between the amplitude of variation in the indoor RH with and without taking into account the hygric buffer capacity of the walls (A < A\({}_{0}\) in which A\({}_{0}\) corresponds to the case without moisture capacity). A low \(f\) ratio represents a higher quality of comfort. The results obtained are presented in Figure 12 and Table 5. Figure 12 shows the variation in the \(f\) coefficient according to the classification of the MBV suggested by the NordTest project [7]. Note that the \(f\) value decreases with increasing moisture buffering capacity; therefore, a lower \(f\) coefficient is observed for a higher MBV value, as shown in Figure 12 and Table 5. When the MBV is classified from negligible to moderate, the \(f\) value decreases from 1 to 0.65 compared to 0.39 to 0.22 for the excellent MBV classification. Note that beyond the MBV value of 3.5 g/(m\({}^{2}\)%RH), the \(f\) value decreases very slowly and tends towards an asymptotic value which means that the moisture buffering potential of BBM has been fully utilized. In addition, it can be observed in Table 5 that indoor RH\({}_{\text{min}}\) increases with the increased MBV value, contrasting with RH\({}_{\text{max}}\), which can be explained by the phenomenon of water vapor sorption (adsorption and desorption) of BBM.  
The results obtained are interesting and confirm that the use of bio-based building materials which are hygroscopic thanks to the microstructure of vegetal fibers results in higher hygothermal comfort in buildings. This conclusion is supported by other studies in the literature [30; 32; 51].  
Figure 12: Impact of moisture buffer classification on \(f\) value.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**MBV** & **RH\({}_{\text{i,max}}\)** & **RH\({}_{\text{i,min}}\)** & **A** & **(Amplitude)** & \(f=\text{A}/\text{A}_{0}\) \\ \hline
0 & 0.73 & 0.50 & A\({}_{0}=0.23\) & 1 \\ \hline
0.5 & 0.7 & 0.51 & 0.19 & 0.83 \\ \hline
1 & 0.67 & 0.52 & 0.15 & 0.65 \\ \hline
1.5 & 0.65 & 0.54 & 0.11 & 0.48 \\ \hline
2 & 0.63 & 0.54 & 0.09 & 0.39 \\ \hline
2.5 & 0.62 & 0.55 & 0.07 & 0.32 \\ \hline
3 & 0.62 & 0.56 & 0.06 & 0.27 \\ \hline
3.5 & 0.61 & 0.56 & 0.05 & 0.22 \\ \hline
4 & 0.61 & 0.56 & 0.05 & 0.22 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Impact of moisture buffer on indoor relative humidity variation.