## 4 Discussion
### Adaptation Solutions to Reduce Overheating Risk  
Five adaptation options are tested in both reference buildings to reduce the risk of overheating brought by climate change and current retrofit practices. Table 9 lists a summary of the tested options and details. Insulation, shading, thermal mass, and ventilation measures are tested to establish the most effective strategy to lower the overheating risks in reference buildings. Among the four climate projections, M2 shows the highest overheating risk for both reference buildings. Following a worst-case scenario approach, M2 is used to test the feasibility of adaptation solutions. Table 10 shows the results of the simulations as a matrix of all adaptation options in each reference building for each time period. The colour of the table ranges from green (most effective options) to red (least effective options) for each time scenario. Moreover, the overheating hours of un-retrofitted cases and retrofitted with current best practice scenarios are presented for comparison. In living rooms, reduced thermal insulation is not an effective option to mitigate overheating in most of the scenarios (Table 10). It only performs well at present scenarios in Climate zone II, where the temperature is relatively low and overheating problem is modest, suggesting that improved insulation level is not a main factor exacerbates overheating. Similarly, [PERSON] et al. [51] designed a comparative study to isolate the effect of insulation on overheating. The results demonstrate that insulation only accounts for up to 5% of overall overheating response. \begin{table}
\begin{tabular}{c c c} \hline \hline
**No. of Options** & **Adaptive Solutions** & **Details** \\ \hline \multirow{3}{*}{1} & \multirow{3}{*}{Less insulation} & The thickness of insulation for external walls is \\  & & 6 cm while the insulation for roof and ground floor \\  & & remains unchanged. \\ \hline \multirow{3}{*}{2} & \multirow{3}{*}{Extra shading} & The wooden shutter of the window is on when the indoor temperature is higher than 24 \({}^{\circ}\)C. \\ \hline \multirow{3}{*}{3} & \multirow{3}{*}{Extra thermal mass} & 3.6 m\({}^{3}\) natural stone, with a volumetric heat capacity \\  & & equivalent to 2.1 MJ/m\({}^{3}\)K, added as floor slabs. \\ \hline \multirow{3}{*}{4} & \multirow{3}{*}{New ventilation strategy (a)} & The ventilation is active when (i) the room is \\  & & occupied, (ii) T\({}_{i}\) > 24 \({}^{\circ}\)C, T\({}_{e}\) >18 \({}^{\circ}\)C, (iii) T\({}_{i}\) > T\({}_{e}\) (the difference with the original ventilation is that the original ventilation is that the original ventilation is active when \\  & & T\({}_{i}\) > T\({}_{e}\) + 3 \({}^{\circ}\)C). \\ \hline \multirow{3}{*}{5} & \multirow{3}{*}{New ventilation strategy (b)} & The ventilation is active when (i) T\({}_{i}\) > 24 \({}^{\circ}\)C, \\  & & T\({}_{e}\) >18 \({}^{\circ}\)C and (ii) T\({}_{i}\) > T\({}_{e}\) + 3 \({}^{\circ}\)C. (the room does not have to be occupied) \\ \cline{1-1}  & & have to be occupied) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Tested adaptation options. T\({}_{i}\) = Indoor temperature, T\({}_{e}\) = Outdoor temperature. The use of wooden shutters to reduce solar gains could mitigate overheating risk considerably in both living rooms (Table 10). Here, the wooden shutter refers to the lower where the wooden slats are contained within a shutter panel (Figure 14). It offers high solar protection while it does not obstruct the ventilation. Many historic buildings in South Tyrol used to have hinged shutters, (as seen in one of the reference buildings of this study depicted in Figure 15). However, in the course of buildings' history, they underwent several interventions, including the removal of these shutters. Considering the significance of shutters on overheating reduction, it is recommended to restore the historic shutters, and close the shutter to prevent excess solar gains. Extra thermal mass has the least effect on overheating control; therefore, this option is not suggested to mitigate overheating.