# Post-Occupancy Evaluation in High-Rise Apartent Buildings in Vietnam
## 3 Results and Discussion
### Impact of OB on the Indoor Thermal Environment  
This study analyzes the indoor environments of the 49 investigated apartments under different room states during different seasons, using data collected from June 2020 to June 2021 (one year). The period from May to September is classified as the cooling season due to the high outdoor air temperatures and the increased electricity consumption associated with AC usage, while the remaining months are categorized as the non-cooling season. Based on occupancy status, the rooms are classified into two basic states: occupied and unoccupied. During the cooling season, occupied rooms are divided into two operating states: AC-on and AC-off.  
Figure 6: Typical cooling setpoint temperatures based on measurements and surveys (N = sample size).  
Using box plots, Figure 8 compares the bedroom and living room temperatures across different room states and seasons. The wall-mounted data loggers measure the room temperature close to the operative temperature. During the non-cooling season, occupancy state and room type have little impact on room temperature. The median room temperature is around 25 \({}^{\circ}\)C during non-occupied periods and slightly lower at around 24 \({}^{\circ}\)C during occupied periods. This difference can be attributed to nighttime occupancy, as outdoor air temperatures tend to be lower at night than during the day.  
In the cooling season, similar trends are observed in unoccupied and AC-off room states, but room temperatures are significantly higher due to elevated outdoor air temperatures. Without AC operation, the median room temperature in bedrooms and living rooms exceeds 30 \({}^{\circ}\)C. When AC is used in bedrooms, the median room temperature decreases by approximately 4 K. However, in the living rooms, the median room temperature remains slightly higher due to the shorter AC operation durations, as discussed in Section 3.2.  
Figure 8: Comparison of room temperatures under various room states during different seasons.  
Figure 7: Overview of monthly electricity consumption and the average monthly outdoor temperature.  
Figure 9 compares the relative humidity levels in bedrooms and living rooms across different room states and seasons using box plots. During the non-cooling season, the relative humidity remains similar in both room types regardless of occupancy state, with a median value of around 75%, which exceeds the recommended range specified in the local design standard. Due to the absence of humidity control equipment, indoor relative humidity varies widely, ranging from a minimum of about 40% to a maximum exceeding 95%.  
When the AC is not in use during the cooling season, the median relative humidity in bedrooms and living rooms remains around 75%, largely unaffected by the occupancy state. While the maximum measured relative humidity decreases slightly due to the higher indoor temperatures, it still exceeds 90%. Meanwhile, the humid and rainy climate causes the minimum relative humidity to rise above 55%.  
Since AC cooling is accompanied by dehumidification, significant reductions in relative humidity are observed in the AC-on state, with the median value dropping to about 60%. However, relative humidity varies considerably due to differences in AC operating durations and cooling control strategies. Notably, excessive dehumidification in some rooms can negatively impact occupant comfort and health, leading to unnecessary energy consumption.