## 3 Results and Discussion
Considering a ventilation gap between two batnens (0.8 \(\times\) 0.03 m\({}^{2}\)), the air flow ranged between 5.2 m\({}^{3}\)/s and 21.6 m\({}^{3}\)/s. The quality of the hygrothermal model was assessed by comparing the values of the in situ measurements of VAT, VAM, VVP, and SST with the modelled correspondent by calculating linear regression functions between measured and modelled values of the same quantity (Table 3). The coefficient of correlation (\(R^{2}\)) between VAT and VAT_model was 0.99, and VAT was on average 0.4 \({}^{\circ}\)C underestimated by the model. \(R^{2}\) between SST and SST_model accounted for 0.99 and overestimated the real value on average by 0.1 \({}^{\circ}\)C (Figure 7). The interdependence of VAM and VAM_model was  
Figure 8: Air speed in the ventilation layer over the total measuring time. characterized by an \(R^{2}\) of 0.90, whereby the model overestimated VAM by 3% (Figure 4). The coefficients of determination of the VAT and SST models are high. The fit of the VAM model was, considering the high variability of the air moisture [26], adequate. The vapour pressure, which is a characteristic for the water in the air, was modelled, and VVP_m deviated on average 10 Pa or 0.9% from VVP (\(R^{2}\) = 0.96). This suggests that the general trend in VVP was correctly traced by VVP_m. The modelled moisture content of the shingles' upper layer (EMC_w_u_m) was on average 34% (SD = 22%), while that of the lower layer (EMC_w_m) was on average 23% (SD = 13%). The EMC of this study was not measured directly, but derived from the model [30]. A lower bound for the modelled data was EMC, determined according to [PERSON] [28], representing the EMC without rain influence, which was in good agreement with the modelled values whenever the level of precipitation was low during summer 2018 (Figure 9). Literature values report an average moisture content of unsheltered weathered wood in Sweden, mounted with an angle of 45\({}^{\circ}\), of 46% for pine sapwood and 25% for pine heartwood [32]. EMC_w_u_m in this study varied between the two values. The source cited supports the modelled results of the current study, but uncertainty is present; therefore, the results for EMC should be rather interpreted as basic trends, and they were primarily used to evaluate differences in the operation mode of the ventilation in this study. The MC of the upper shingle layer was predominantly affected by precipitation, causing the peaks in Figure 9. EMC_w_m was higher than EMC with an average of 16% (SD = 4%) (the moisture content of the shingles if there was no precipitation). Hence, the lower shingle layer was also significantly influenced by precipitation throughout the year, being stronger at the beginning (the peaks of precipitation are delayed in the EMC of the shingles in Figure 9). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Measured or Modelled Value** & & **Mean** & **SD** & **Min** & **Max** & \(R^{2}\) \\ \hline VAT & \({}^{\circ}\)C & 11.3 & 10.0 & \(-\)14.7 & 39.5 & \\ VAT\_m & \({}^{\circ}\)C & 10.9 & 9.5 & \(-\)15.1 & 36.1 & 0.99 \\ VAM & \% & 74 & 16 & 22 & 99 & \\ VAM\_m & \% & 77 & 17 & 20 & 99 & 0.90 \\ SST & \({}^{\circ}\)C & 10.6 & 9.7 & \(-\)16.9 & 35.5 & \\ SST\_m & \({}^{\circ}\)C & 10.7 & 9.5 & \(-\)15.2 & 36.3 & 0.99 \\ VVP & Pa & 1156 & 605 & 135 & 3351 & \\ VVP\_m & Pa & 1146 & 570 & 158 & 2900 & 0.96 \\ EMC\_w\_m & \% & 23 & 13 & 10 & 54 & \\ EMC\_w\_red\_m & \% & 24 & 15 & 10 & 57 & \\ EMC\_w\_u\_m & \% & 34 & 22 & 9 & 85 & \\ EMC\_w\_u\_red\_m & \% & 34 & 23 & 9 & 86 & \\ EMC\_n\_mod & \% & 26 & 15 & 11 & 57 & \\ EMC\_n\_red\_m & \% & 27 & 18 & 10 & 64 & \\ EMC\_e\_m & \% & 22 & 13 & 10 & 53 & \\ EMC\_e\_red\_m & \% & 23 & 14 & 10 & 55 & \\ EMC\_s\_m & \% & 20 & 10 & 10 & 46 & \\ EMC\_s\_red\_m & \% & 20 & 10 & 9 & 46 & \\ EMC\_w\_unvent\_m & \% & 26 & 18 & 10 & 65 & \\ EMC\_w\_opt\_m & \% & 23 & 13 & 10 & 54 & \\ EMC & \% & 16 & 4 & 10 & 54 & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Descriptive statistics of modelled values and correlations with measured values.