## 2 Materials and Methods
### UHI Indirect Impact Evaluation--Building's Energy Performance Evaluation Studies  
As previously explained, the UHI indirect impact evaluation relates to the building's energy performance, as well as the effect of the facade skin and the cavity function primarily on the reduction of the cooling loads and, consequently, also on the inner comfort.  
For the evaluation process, the studies were focused mostly on the dual-cavity function in the cooling- and heating-dominated periods, to simulate the dynamic air and heat flows throughout the day and to visualize the temperature fluctuations through the cavity section to the interior. For these purposes, the studies were divided into analyzing the summer and winter situation, with the summer one to be the most critical one for the evaluation of the proposed facade system on the indirect impact, and the winter one to work more as a validation control and understanding of the proposal for the cavity function. During the summer scenario, the focus was placed on estimating the cooling demands and assessing the parameters and boundary conditions that influence the performance and, in the end, comparing the results to the existing single facade scenario. On the contrary, for the winter situation, it was more insightful to simulate the heat and air flows inside the closed cavity zones and to visualize the temperature fluctuations from the exterior to the interior of the building to assess the effect of the thermal heat buffer zones and to make a comparison with different boundary conditions and cavity widths. Finally, as a side study, a daylight analysis was conducted to evaluate the shading effect in the interior of the building with different component scales, to what extent the inner comfort is affected, and the percentage of reduction of the admitted daylight, in relation to the existing facade with no external sun-shading.  
The study workflow for these analyses can be seen in the flowchart below (Figure 10). The approach followed an interoperability and decoupling method, due to software limitations and to exploit the possibilities of the most suitable software for the requirements of each study. More specifically, for the cooling demands analysis, the Honeybee plug-in in Grasshopper was used, which enables the simulation of the different thermal zones, internal loads, and ventilation options and can provide an estimation of the energy use intensity (EUI) indicator for the analyzed periods. Since it is an early design stage, this approach provided sufficient and accurate enough results to give a first indication of the building's energy performance.  
In parallel, since the cavity system functions in a more dynamic way, CFD simulations were also necessary. These were realized using the open-source online digital software SimScale [17], which could be compatible with geometries imported from Rhino, and, without necessarily requiring extensive experience in fluid dynamics and CFD modeling, it can provide satisfactory, yet with certain simplifications, results. This method was coupled with data provided by the Ladybug radiation analysis, which was used to retrieve the solar radiation value to be assigned as an additional radiation heat flux (W/m\({}^{2}\)) on the facade surface for one day. The SimScale simulations were used to visualize the full height cavity flows during the summer situation and the impact of air inlets and outlets, but mostly to also visualize the winter cavity system.  
Finally, for the winter situation and as a complementary analysis, the THERM plug-in in Grasshopper was also used, which can provide the temperature fluctuations from the outside to the inside boundary, by selecting material properties and boundary conditions, including the layer behind the cavity zone. Even though it is not a dynamic simulation, it could still provide sufficient results for a specific date and time condition.