## 3 Results and Discussion  
### Sorption/Desorption Kinetic  
The moisture uptake and release variations over time between 50% and 80% RH are shown in Figure 3. All the tested assemblies showed a similar trend for moisture sorption. The samples absorbed moisture when the relative humidity increased and desorbed moisture when the relative humidity decreased. The increase in weight was due to the absorbed liquid water in the pores of the materials. Water vapour cannot cause such an increase as its density is too low, and therefore the water vapour in the air must be stored by the material in the form of liquid water [33]. Steady state was not reached for the mass after 324 h. During absorption, the mass increase was higher than the decrease during desorption. The uptake and release masses for individual wall assembly samples are shown in Table 2. At the beginning of the exposure to lower relative humidity, the desorption was faster than the adsorption during the exposure to higher relative humidity. The water vapour was released quickly, and after a period of rapid release, the process slowed down. The results show that desorption occurs faster than adsorption, and this phenomenon is also a clear illustration of hysteresis within the hygroscopic samples.  
Comparing the results for moisture transfer, it is observed that the rate of moisture uptake in Assembly D was higher than in Assembly C, at 0.96% and 0.84%, respectively. Assembly D and Assembly C differed only in the inner layer. In Assembly D this was flexible wood fibreboard (Pavaflex) (3.2.2); in Assembly D it was mineral wool (ECOSE) (4.12) and an air layer. The situation was similar  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **\(\Delta\)MC Uptake at 80\% RH (\%)** & **\(\Delta\)MC Release at 50\% RH (\%)** \\ \hline Assembly D & 0.96 & 0.77 \\ Assembly C & 0.84 & 0.69 \\ Assembly B & 0.82 & 0.75 \\ Assembly A & 0.57 & 0.42 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Variation in moisture uptake and release.  
Figure 3: Sorption/desorption kinetics at 80% and 50% RH.  
for Assemblies A and B, which also differed only in the interior composition. The moisture uptake in Assembly B was 0.82% and that in Assembly A was 0.57%.  
Analysing the properties of individual material layers (Table 1), it is seen that the inner layers (wood fibreboard (Pavaflex) (3.2.2) and mineral wool (ECOSE) (4.12)) had a similar vapour diffusion resistance factor \(\upmu\) of 3-5, so, in this case, this was not a factor influencing the obtained differences in results. However, mineral wool showed negligible moisture sorption (Figure 2) compared with wood fibreboard, and this is certainly associated with the fact that Assembly B absorbed more moisture than Assembly A and Assembly D absorbed more than Assembly C.  
An analysis of the tested cases allows us to conclude that materials with a higher density absorb a greater amount of water. Comparing further the sorption kinetics shown in Figure 4, it can be seen that Assembly B and Assembly C had almost the same moisture uptake: Assembly B had 0.82% and Assembly C had 0.84%. These results indicate than the outer finishing layers of the material had an effect on the inner layers and may reduce their capacity for moisture buffering.