## 3 Results
### Experimental Results
\[f=\frac{T_{i,max}-T_{i,ave}}{T_{e,max}-T_{e,ave}} \tag{9}\]  
\[\Phi=t_{Ti,max}-t_{Te,max} \tag{10}\]  
Here, \(T_{i,max}\) is the maximum (peak) indoor surface temperature (\({}^{\circ}\)C); \(T_{i,max}\) is the average indoor surface temperature (\({}^{\circ}\)C); \(T_{e,min}\) is the peak outdoor surface temperature (\({}^{\circ}\)C); \(T_{e,min}\) is the average exterior outdoor temperature (\({}^{\circ}\)C); \(t_{Ti,max}\) are the peak indoor temperature time points (h); and \(t_{Te,max}\) are the peak outdoor temperature time points (h). Experimental results from the transient-state thermal inertia test in thermal flux Direction 1 and 2 are shown in Figures 5 and 6, respectively. For these tests, relative humidity was 70%, both inside and outside the hot-box. Equations (9) and (10) were used to calculate the decrement factor and time lag. Table 4 shows the transient-state results obtained both in the laboratory and following the empirical methodology according to the ISO 13786 standard [3]. These values may be useful for the practical application of this enclosure as an element of construction. Depending on the direction of thermal flux, the experimental time lag values ranged from 13.58 to 14.83 h. Following the empirical methodology of the ISO 13786 standard [3], a time lag of 10.86 h and a decrement factor of 0.1249 was reached. The empirically calculated time lag and decrement factors were more restrictive than those obtained experimentally. Thermal inertia tests in Direction 1 and 2 showed significant differences in terms of time lag (1.25 h difference) and decrement factor (23% difference), as shown in Table 4.  
Figure 7 shows the temperature and heat flux experimental results for Direction 2. The indoor temperature exhibited small variations in the range between 23 and 25 \({}^{\circ}\)C, while the outdoor (hot-box) temperature followed 24 h cycles and the heat flux ranged from \(-\)1.3 to 4.3 W/m\({}^{2}\). High time lag and low decrement factor values provide the optimal comfort conditions inside buildings. Therefore, the optimal wall configuration we found was Direction 2, in which the lightweight mortar layer insulation LWMA was exposed to the outdoor conditions (those of the hot-box). This was the configuration that we used in the subsequent numerical analysis. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Case** & **\(\mathbf{\Phi}\)** (h) & **\(\boldsymbol{f(\boldsymbol{\cdot})}\)** \\ \hline Direction 1 & 13.58 & 0.0313 \\ \hline Direction 2 & 14.83 & 0.0241 \\ \hline Empirical (s/ISO 13786) & 10.86 & 0.1249 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Transient-state thermal results. Figure 6: Transient-state test results showing the decrement factor and time lag in thermal flux Direction 2. Due to the hygroscopic properties of insulating materials, they can be affected by minor variation in the moisture or ambient temperature of a laboratory. As experimental tests are expensive and time consuming, it was necessary to build the 1 m\({}^{2}\) wall, place it in the hot-box and wait for at least two weeks for materials to stabilize before testing, so as not to bias results.