# Thermal Comfort and Sustainability in University Classrooms: A Study in Mediterranean Climate Zones
## 3 Results
### Adaptive Thermal Comfort Model  
Figure 7 shows a scatter plot of the linear regression between \(T_{c}\) and \(T_{m}\), in both modes of operation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Operation Mode**} & \multirow{2}{*}{**N**} & \multicolumn{3}{c}{\(T_{c}\) (\({}^{\circ}\)C)} \\ \cline{3-5}  & & \(\alpha\) = 0.25 & \(\alpha\) = 0.33 & \(\alpha\) = 0.50 \\ \hline AC & 79 & 26.23 (\(\pm\)3.18) & 25.84 (\(\pm\)2.46) & 25.42 (\(\pm\)1.71) \\ NV & 195 & 21.42 (\(\pm\)3.52) & 22.74 (\(\pm\)2.76) & 24.14 (\(\pm\)2.15) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comfort temperature based on the Griffiths method for AC and NV operation modes. Equations (5) and (6) represent the adaptive thermal comfort model for AC and NV modes, respectively. \[T_{c}=0.1859\cdot T_{rm}+20.305\left(R^{2}=0.1627\right) \tag{5}\]  
\[T_{c}=0.2530\cdot T_{rm}+17.354\left(R^{2}=0.1783\right) \tag{6}\]  
For the AC mode, the average predicted \(T_{c}\) was 25.83 \(\pm\) 1.00 \({}^{\circ}\)C, ranging from a maximum value of 27.31 \({}^{\circ}\)C to a minimum of 24.60 \({}^{\circ}\)C. For the NV mode, the average predicted \(T_{c}\) was 24.14 \(\pm\) 2.15 \({}^{\circ}\)C, with temperatures ranging from a maximum of 31.32 \({}^{\circ}\)C to a minimum of 19.10 \({}^{\circ}\)C. As can be seen, for both modes of operation, the proposed models predict temperature values in the comfort zone [47]. Figure 8 shows the distribution of comfort temperatures according to the two operating modes studied. In NV mode, the most represented comfort range was 24-26 \({}^{\circ}\)C, followed by the 22-24 \({}^{\circ}\)C and 26-28 \({}^{\circ}\)C ranges, while the extreme ranges (18-20 \({}^{\circ}\)C and 30-32 \({}^{\circ}\)C) were much less represented. Similarly, in AC mode, the predominant comfort range was also 24-26 \({}^{\circ}\)C, followed by the 26-28 \({}^{\circ}\)C range. However, in AC mode, comfort temperatures were more strongly concentrated in these ranges, evidencing greater consistency and a more limited range compared to NV mode, which shows greater variability in thermal preferences due to environmental conditions and individual differences in thermal perception [62]. [PERSON]  
Figure 8: Comfort temperature distribution according to operating mode (NV and AC). Figure 7: Adaptive thermal comfort model for AC and NV modes. et al. found that the most comfortable temperature ranges in university classrooms were 24-26 \({}^{\circ}\)C in NV mode and 23-24 \({}^{\circ}\)C in AC mode, with greater variability also in naturally ventilated classrooms [33]. Comparison with International Standards  
Figure 9 presents a comparison between the comfort temperature and the comfort zone using different approaches: the proposed model, the ASHRAE 55 standard [2] (Figure 9a), Norm EN 16798-1:2020 (Figure 9b) and the CIBSE guide [78] (Figure 9c). The dashed lines in the graph indicate the limits of the comfort ranges set by the mentioned standards, while the grey solid lines represent the \(T_{c}\) defined by these standards. The yellow (for NV mode) and blue (for AC mode) solid lines reflect the comfort temperature calculated according to the model proposed in this study. First, Figure 9a compares the proposed model with the ASHRAE 55 standard, whose equation for the NV mode of operation is defined as \(T_{c}\) = 0.31\(\cdot\)\(T_{pmu(out)}\) + 17.8 [2]. To simplify the analysis, the average prevailing outdoor air temperature (\(T_{pmu(out)}\)) was assumed to be equivalent to \(T_{m}\)[47]. According to the acceptability zones established by this standard, 50% of the measurements made were found to be within the 90% comfort level (black dashed line), 73.33% within the 80% comfort zone (green dashed line) and 26.67% outside the acceptable zones.