# Study of the Hydrothermal Behavior of Wood Fiber Insulation Subjected to Non-Isothermal Loading
## 2 Materials and Methods
### Experimental Setup  
The experimental setup proposed permits studying the behavior of a multilayer wall of 1 m\({}^{2}\) under different hygothermal loadings [21; 22]. It is designed to provide experimental observations in order to:  
* Better understand the hygothermal phenomena involved during the transfer. * Obtain sufficient data to validate or build predictive Heat, Air and Moisture transfer models. * Characterize transport properties at the wall scale. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**RH (\%)** & 0 & 15 & 22.5 & 30 & 43 & 45 & 60 & 66 & 75 & 90 & 93 & 97 \\ \hline \(\textbf{U}_{Sorption}\) & 0.00 & 3.10 & 4.10 & 4.88 & 6.06 & 6.25 & 8.08 & 9.14 & 11.27 & 16.70 & 18.14 & 20.26 \\ \hline \(\textbf{U}_{Desorption}\) & 0.00 & 3.60 & 4.74 & 5.61 & 6.81 & 6.99 & 8.73 & 9.74 & 11.79 & 17.15 & 18.58 & 20.70 \\ \hline \(\textbf{U}_{Mean}\) & 0.00 & 3.35 & 4.42 & 5.25 & 6.43 & 6.62 & 8.40 & 9.44 & 11.53 & 16.92 & 18.36 & 20.48 \\ \hline \(\textbf{SD}\) & - & 0.86 & 0.86 & 0.87 & 0.89 & 0.89 & 0.93 & 0.94 & 0.96 & 0.97 & 0.98 & 0.98 \\ \hline \multicolumn{11}{c}{\(RH\): relative humidity (\%) and \(U\): mass water content (\%). \(SD\): Standard Deviation.} \\ \end{tabular}
\end{table} 
Table 1: Mass water content as a function of relative humidity expressing sorption–desorption curves of wood fiber insulation at 20 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c} \hline \hline
**Hygrothermal Property (unit)** & **Value** \\ \hline Apparent density (kg/m\({}^{3}\)) & 146 \\ Porosity (\%) & 90–99 \\ Water vapor resistance coefficients (-) & 2.73 \\ Thermal conductivity (W/(m-K)) & \((38+0.28\cdot U+0.108\cdot T)\cdot 10^{-3}\) \\ Specific heat (J/(kg\(\cdot\)K)) & \(1103.1+11.271\cdot T\) \\ \hline \multicolumn{11}{c}{\(U\): mass water content (\%) and \(T\) : Temperature (\({}^{\circ}\)C).} \\ \end{tabular}
\end{table} 
Table 2: Hygrothermal properties of the wood fiber insulation. Figure 1: Mean adsorption isotherm for wood fiber insulation. To achieve this, the wall studied was placed between two compartments with a volume of \(0.5\times 1\times 1\) m\({}^{3}\) whose role was to maintain the desired thermal and moisture loadings (see Figure 2). The humidity of compartment 1 was regulated using a Saturated Salt Solution (SSS), while its temperature was regulated by fluid-air exchangers linked to a circulation cryostat. Compartment 2 had two operating modes with natural and forced convection. The first mode was obtained with humidity regulation using the SSS and temperature regulation with a climatic chamber in remote mode. The second mode was obtained directly with the climatic chamber that pulsed treated air parallel to the wall studied at a controlled flowrate. Using the SSS for regulation permits measuring the vapor flowrate exchanged between the air in the compartments and the wall, by monitoring the evolution of the mass of SSS as a function of time. Fans were installed to homogenize the temperature and humidity in each compartment. Heating and cooling powers of regulation systems were sufficiently large to quickly reach the desired temperature. The vapour stream obtained by the SSS were limited. The mass of the used SSS (both compartments were equipped with an adapted balance) for relative humidity control was about 2.5 kg and its exchange surface area was about \(0.46\times 0.3\) m\({}^{2}\). The compartments were composed of two elements, an internal box and an external box that served as a thermal guard. They were made of stainless steel with airtight welds controlled by penetrant testing. Since the two compartments were regulated differently, their designs and compositions were different.