## 3 Results and Discussion
### Energetic Analysis  
The difficulty of rehabilitating classified buildings makes the improvement of windows and the use of thermal insulation by the interior interesting measures to improve the indoor climate and achieve energy savings. Figure 9: Comparison between the indoor air and the surface conditions: (**a**) indoor air temperature and internal surface temperatures; (**b**) density heat flow rate of the between the surfaces and the interior environment. In the previous section, the impossibility of defining similar energy-saving strategies for the whole of Europe was concluded, since the regional climate has a determinant influence on how the buildings react to a certain strategy. For example, in southern European countries with greater cooling needs, the rehabilitation may involve the reduction of the SHGC; for these cases, the opaque envelope plays a minor role. On the other hand, in the colder cities of central and northern Europe, the highest heating needs impose different solutions that may warrant the implementation of thermal insulation and windows refurbishment. The results of the sensitivity study relating the impact of the climate control strategies, U, U\({}_{\rm w}\) and the SHGC on the global annual energy consumption for the case of Lisbon can be seen in Figure 10. The reference energy consumption is also presented, allowing us to effectively analyze the impact of each one of the rehabilitation scenarios in the final result. Figure 10: _Cont._  
Focusing the attention on the improvement of the thermal transmittance of the opaque envelope, it was concluded that this refurbishment scenario has a reduced impact on the total energy consumption. Using the optimization model, an ideal U-value of 0.30 W/m\({}^{2. }\)\({}^{\circ}\)C was obtained, but only resulting in a reduction of 5.40% in the annual energy consumption (3.45 kWh/m\({}^{2}\) per year). The replacement of the current windows with thermal transmittances of 3.63 W/m\({}^{2. }\)\({}^{\circ}\)C has an even a lower impact on the energy reduction, resulting in a maximum energy saving of 1.25% (0.80 kWh/m\({}^{2}\).year) for the optimum thermal transmittances of 2.35 W/m\({}^{2.}\)\({}^{\circ}\)C. As regards the SHGC, the panorama is slightly different, achieving savings of 22% (14 kWh/m\({}^{2}\).year) by replacing the original windows with a global SHGC of 0.38 with ones with a global SHGC of 0.1. It is interesting to note that for the higher values of SHGC, the window refurbishment results in higher energy consumptions compared with the reference case: above an SHGC of 0.52 for a U-value equal to 1.36 W/m\({}^{2. }\)\({}^{\circ}\)C or above 0.35 for a U-value equal to 0.30 W/m\({}^{2.}\)\({}^{\circ}\)C. These values were obtained by the interception between the curves for a U\({}_{\rm w}\) equal to 3.63 W/m\({}^{2. }\)\({}^{\circ}\)C and that for a U\({}_{\rm w}\) equal to1.53 W/m\({}^{2.}\)\({}^{\circ}\)C. This fact is justified by the reduction of losses which contributes for the increase in the internal temperature and consequently the increase in the cooling needs. For the less demanding set-point, this inversion occurs for a lower SHGC: 0.24 for a U-value of 1.36 W/m\({}^{2. }\)\({}^{\circ}\)C and 0.16 for a U-value of 0.30 W/m\({}^{2.}\)\({}^{\circ}\)C. Analyzing the impact of the climate control strategy was purposely left to the end as it could lead to significant savings without any initial investment. Savings of 52% in the energy consumption (33.30 kWh/m\({}^{2}\).year) were achieved by replacing the original set-point of 20-22 \({}^{\circ}\)C for the temperature and 50-60% for the RH with the set-point of 18-25 \({}^{\circ}\)C during the opening hours and 16-25 \({}^{\circ}\)C in the nighttime concerning temperature and 40-60% for the relative humidity without any further intervention. This change led to savings ca. 10 times higher than those obtained for the opaque envelope refurbishment, ca. 42 times higher than those achieved by the window refurbishment and ca. 2.4 times higher than the one obtained for an SHGC equal to 0.1.