## 3 Results
### UHI Indirect Impact Evaluation
#### 3.2.2 Thermal Analysis  
Heat and Air Flows Simulations  
The results from the winter situation (Figure 25) showed that there is an increase in the surface temperature around the inner boundary of up to 25 \({}^{\circ}\)C with a further increase on the top surfaces of the cavity boundaries due to the air and heat stratification. Similar results were found through the THERM static temperature fluctuation simulation, which showed a heat buffer accumulated outside the insulation layer, reducing the heat losses and the temperature difference between the interior and the exterior during the cold months. It can also be noticed that the simulations realized through SimScale capture only an hour of  
Figure 24: Energy balance charts (**left**) and EUI of the cooling loads charts (**right**) for each case study shown in Figure 23.  
operation and, in that way, show the effect in its starting moments when the cavity begins to heat up, while the THERM model shows the temperature fluctuations as a static building construction with no incoming airflow, which, however, receives a constant additional radiation heat on the outer boundary layer. In this sense, Case#1 and the THERM model can be approximate representatives of the two boundary conditions, the beginning and the peak of the thermal effect, respectively, with the SimScale one to also highlight the reverse situation when the model slowly transcends back to its original cool state after the solar radiation intake is reduced during the late afternoon hours.  
In addition, in Case#2, there is an increase in the temperature inside the cavity and the convective effect of the inner pyramid volume is also more evident, which can be justified by the increase in the heat flows induced by the increased air movement that is heated up when entering the cavity. However, this creates, at the same time, a constant air influx, which leads to heat losses at similarly high speeds, so the heat buffer effect is then being reduced. Lastly, in Case#3, the narrower cavity on top also led to an increase in temperature due to less air volume requiring less time to reach a higher temperature. However, as seen by the cooling demands analysis and despite possible winter benefits, a narrow cavity would cause an overheating during the summer, which is more critical to mitigate for the scope of the current study. It can, therefore, be concluded that the function during the cold seasons as a multiple-cavity system can have the potential to offer additional benefits as a thermal buffer zone for the reduction of the heat losses.  
Regarding the summer scenario, the results summarized below (Figure 26) showed similar behavior inside the cavity, with higher temperatures on the boundary surfaces and in the narrow air volumes. The difference here is that there is a slight reduction of accumulated heat when there are no air inlets between the interior building spaces and the continuous cavity zone, as in Case#2. In accordance with the conclusions from the cooling demands analysis, the air entering the cavity is warmer than the interior, causing overheating of the cavity and introducing hot air to the interior instead, in a greenhouse manner. The temperatures reached are above the outdoor ambient temperature, ranging in average from 35 \({}^{\circ}\)C-37 \({}^{\circ}\)C, with some local intensified boundary areas that exceed those limits. This can also be seen in the areas around the air inlets, where there is a local increase in temperature. Case#3 showed negligible difference compared to Case#2 and also  
Figure 25: Convective heat transfer analysis simulation results for the winter situation.  
needed to be slightly modified to avoid continuity errors caused by excluding air inlets, so a minimum area of air inlets was also assigned at the bottom of the outer layer instead, to comply with the pressure outlet on top.