# Post-Occupancy Evaluation in High-Rise Apartent Buildings in Vietnam
## 3 Results and Discussion
### Evaluation of Long-Term Thermal Comfort  
The long-term indoor thermal environment of the 49 investigated apartments is evaluated using the methodology described in Section 2.3. Figure 10 compares the annual overcooling and overheating probabilities for the measured bedrooms and living rooms. Overall, the probability of overheating (defined as the room temperature exceeding the 80% upper limit of the adaptive model) during the occupied hours is low. Notable exceptions include the living room of Apartment 30 and the bedroom of Apartment 31, where overheating probabilities reach 10% and 7%, respectively. Both rooms share common characteristics: west-facing windows and infrequent AC usage due to energy cost concerns. As a result, these spaces experience high summer temperatures due to increased solar radiation exposure. However, the impact of elevated air speed on thermal comfort is not accounted for due to measurement limitations. Since the occupants of these rooms prefer using electric fans in summer, the actual thermal environment may be more tolerable than the evaluation suggests.  
Figure 9: Comparison of relative humidity under various room states during different seasons.  
Conversely, overcooling is more prevalent, as residents typically do not use heating equipment. About 70% of the measured rooms have an overcooling probability of more than 10%, with most exceeding 20%. Bedrooms and living rooms within the same apartment  
Figure 10: Comparison of the probability of overcooling and overheating in the bedrooms and living rooms of investigated apartments (n/a: no overcooling/no overheating).  
generally experience similar overcooling conditions. Notably, the living room of Apartment 20 stands out, with an overcooling probability nearing 65%, significantly higher than in other apartments. This can be attributed to its high winter and low summer occupancy rates. Additionally, solar heat gain is limited as the room faces north, resulting in low room temperatures.  
It is worth noting that the adaptive model used in the evaluation is based on the study by [PERSON] et al. [37], which primarily developed the comfort temperature equation using the data collected during the cooling season in Southeast Asia. Limited winter comfort surveys suggest that this model may underestimate occupants' tolerance to cold conditions, implying that the risk of overcooling might be lower than indicated in Figure 9. Further validation of the long-term indoor thermal environment evaluation methodology is needed, particularly through additional occupant surveys conducted during colder months.  
Although the adaptive model does not specify humidity limits, high relative humidity can restrict the effectiveness of adaptive strategies and narrow the comfort range [37]. Moreover, excessive humidity often leads to mold growth, which causes structural damage and increases health risks [41]. The Vietnamese Standard TCVN 14214:2024 [36] recommends an indoor humidity range of 60% to 70%, which is higher than the 40 to 60% range preferred by many international standards [42; 43]. This reflects the local adaptation to hot and humid environmental conditions.