Thermal comfort in mixed-mode cooled houses: A field study in the hot-humid climate of Danang, Vietnam

Natural ventilation is an essential efficient energy strategy for cooling in hot and humid tropical regions. In Vietnam, however, increasing living standards led to a significant rise in the use of air conditioners in housing, resulting in elevated energy consumption. Typically, natural ventilation and fans serve as the primary cooling method throughout the house, while air conditioners—mainly installed in bedrooms—are used only when residents are present and feel hot. Although this mixed-mode cooling method has gained popularity, the indoor thermal environment remains underexplored within the context of Vietnam’s thermal environment. This paper presents the results of an investigation into indoor thermal conditions and residents’ sensations under mixed-mode cooled environments in humid tropical Danang, Vietnam. The study encompasses both air-conditioned and naturally ventilated spaces for a comprehensive comparison. Measurements on environmental parameters and a survey on thermal sensation were conducted among 60 households in Danang from August − October 2022 and June – August 2023. Despite being in a coastal area, the houses were poorly ventilated, and indoor temperatures were often higher than outdoor temperatures. However, most residents reported satisfaction with their indoor conditions. The PMV index was found ineffective in predicting the thermal sensation of houses utilizing a mixed-mode cooling approach. A small group of respondents may have adjusted their expectations to accommodate their actual indoor thermal environment. The study provides insight into indoor thermal conditions and residents’ sensations in the context of Danang housing for further energy-saving initiatives and home thermal comfort.