Simultaneous Influences of Temperature and Airflow on Comfort Perceptions in Residential Buildings in Vietnam

ASHRAE Standard 55 has suggested that airspeeds of 0.2m/s and 0.8m/s set a discomfort limit in air-conditioned and non-air-conditioned buildings. Some previous studies have attempted to determine thermal comfort conditions and desirable air velocities in naturally ventilated buildings in the tropics. They have found that the real indoor airflow has been low and inhabitants have desired more airflow for their satisfaction, with airspeeds higher than the recommended values at up to 1.6m/s. Additionally, those studies have mostly focused on the maximum acceptable airspeeds that extend the upper comfort limit. However, referring to the adaptive comfort approach, although building occupants may accept ‘slightly warm’ temperatures, elevated airspeeds concurrently affect their overall thermal acceptability, particularly in warm-humid environments. This paper examines a simultaneous correlation between thermal and air movement perceptions and expectations of occupants in non-air-conditioned residences in Vietnam. On-site thermal environments and subjective responses to those were investigated in houses of Ho Chi Minh City, which is the context of the study. Within the environments which people found comfortable, most of them preferred more airflow up to 0.8m/s. The value of 0.5m/s can be determined to be a suitable reference point for airflow acceptability to restore human thermal satisfaction indoors.