6 minute read
Thermal Comfort Analysis
6.4 Thermal Comfort Analysis
Step 0 | Base Case
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A base case in the form of a standard room in the existing labor camp context has been established. The requirements and context have been derived from the existing labor camp analysis in Chapter 2. The room is west facing and is airconditioned at a setpoint of 19OC. The WWR has been assumed to be 35% per the Estidama standards. The glazings are fixed and do not allow the adaptive opportunity for natural ventilation.
Standard construction of a reinforced single-leaf CMU wall with single-glazed windows, typical of constructions in the UAE, has been considered.
According to Figure 6.10 During the hot period, the average operative temperature within the room is around 19oC due to the air conditioning. However, in the free-running scenario, the indoor spaces are 6.4oC lower than the outdoors, reaching up to 37oC.
Table 6.1 Model input parameters
Figure 6.9 Step 0: Proposed labor camp room in existing labor camps with WWR 35% (Estidama)
Figure 6.10 Graph showing thermal comfort for base case in typical hot period
Step 1 | Proposed labor camp room in proposed Urban Context with Jali
The room is now placed in the proposed compact courtyard form, and the glazing unit is replaced with the proposed terracotta jali. It is a west-facing unit along the narrow E-W canyon and is free running. Also the number of occupants has been reduced to 2 as per the proposed density (Chapter 2).
It can be seen that the temperature difference between Step 0 and Step 1 is 3.1oC (Figure 6.12). The temperature has dropped closer to the comfort band. This can be attributed to the reduction in solar gains due to the form and the jali. However, further intervention is required to increase the comfort levels within these rooms.
Table 6.2 Model input parameters
Figure 6.11 Step 1: Proposed labor camp room in proposed urban context with jali
Figure 6.12 Graph showing thermal comfort for Step 1 in typical hot period
Step 2 | Addition of Thermal Mass
In Chapter 5, it was concluded that apart from solar gain, conductive heat gain through the building envelope was one of the primary factors that needed to be addressed. Therefore, thermal mass in the form of two-layer compressed earth blocks with mineral wool insulation has been proposed (Goodhew and Griffiths 2005) (Figure 6.13). The vernacular use of these materials has been discussed in Chapter 4.
The resultant graph (Figure 6.16) shows a further temperature drop of 4.7OC from the base case due to a change in the construction materials and the addition of thermal mass.
Additionally, thermal mass in the form of filler slab with earthen pots has been proposed for the roof for the upper floors. The thermal results for the upper floors are in Appendix D.
Figure 6.13 Addition of thermal mass (Source: Goodhew and Griffiths 2005)
Table 6.3 Model input parameters
Figure 6.15 Step 2: Addition of thermal mass
Figure 6.16 Graph showing thermal comfort for Step 2 in typical hot period
Step 3 | Addition of Liwan
A shaded colonnade of 2m depth is introduced to reduce solar gains further. It is in accordance with the sun angles as determined in previous sections. It functions as a transitional space and microclimate modifier.
It is observed in Figure 6.18, that by adding liwan, the temperature further drops by 5.5OC from the base case and is almost within the comfort band, except for peaking during the afternoons when the outdoor dry-bulb temperatures and solar radiation levels are high.
Table 6.4 Model input parameters
Figure 6.17 Step 3: Addition of liwan
Figure 6.18 Graph showing thermal comfort for Step 3 in typical hot period.
Step 4 | Decoupling during the day and Fan Driven Ventilation
As discussed in the climate section, the large variation in day and night temperatures offer the potential for night ventilation in buildings to cool down the temperature using thermal mass. However, during the day, when the outdoor temperatures and solar radiation is high, the rooms can be decoupled using shutters and further cooled using ceiling fans. Based on research, they have the potential to reduce the indoor temperature by 2-3OC (Babich et al. 2017).
The results in Figure 6.21 show a further decrease of 6.4OC from the base case and are well within the comfort zone.
Figure 6.19 Fan driven ventilation and cooling effect of fans (Source: Babich et al. 2017)
Table 6.5 Model input parameters
Figure 6.20 Step 4: Decoupling and fan driven ventilation during the day and night ventilation during the night
Figure 6.21 Graph showing thermal comfort for Step 4 in typical hot period.
Step 5 | Varying Orientations
Finally, the varying urban adjacencies are considered to study the difference in the performance of the rooms based on their orientation and location within the urban context. The previous analysis was for west-facing rooms adjacent to the minor axis EW canyon. Now rooms sharing adjacency to the major axis NS canyon and the open public square are considered. As expected, indoor temperatures and solar exposure also increased with an increase in openness. However, despite the variations, rooms in the proposed orientations fall in the comfort zone for most of this period with an extended adaptive comfort band as discussed in Section 3.3, Chapter 3. Figure 6.24 demonstrates the increase in annual comfort hours in the proposed rooms with each progressive step and strategy.
Conclusion
The analytical work justifies the literature review undertaken earlier by showing the success of the compact courtyard typology, jali, liwan, and thermal mass in mitigating solar heat gain while maintaining adequate daylight. These strategies could now be used to define and develop the built form. It has been illustrated in Figure 6.25.
Table 6.6 Model input parameters
Figure 6.22 Step 5: Varying orientations
Figure 6.23 Graph showing thermal comfort for Step 5 in typical hot period.
Figure 6.24 Annual comfort hours of the proposed labor camp room illustrating the benefits obtained from various microclimatic and passive strategies
Figure 6.25 Built form development
- Lisa Heschong (1979)
