Transient thermal and physiological responses from air-conditioned room to semi-outdoor space in the tropics

This study explored the feasibility of working in a semi-outdoor space in the tropics. Humans can work in the semi-outdoor space for short-term without compromising cognitive performance. However, transient thermal and physiological responses are unclear when people move from an air-conditioned (AC) room to semi-outdoor space. Experiments were carried out to understand transient thermal and physiological responses in Singapore. Eighty-nine tropically acclimatized participants voted on thermal responses in the first 30 min in an AC room of 24 °C and 40 min in a semi-outdoor space from 25.0 to 31.8 °C. Heart rate, skin temperature and skin conductance were measured. After moving to the semi-outdoor space, thermal sensation, thermal comfort and thermal acceptability remained similar without overestimating thermal responses in the first few minutes (p > 0.05). The stabilized times of thermal sensation, thermal comfort and thermal acceptability rapidly were within 1 min due to past thermal experiences and expectations. Mean skin temperature and mean heart rate increased by 0.7 °C (p 0.05) after moving to the semi-outdoor space. The stabilized time of 7 min in mean facial temperature was shorter than the 30 min in the whole body mean skin temperature due to high density of blood vessels in the face. Mean facial temperature was more thermally sensitive than that in the whole body. There was little change in transient thermal and physiological responses after moving to semi-outdoor space. •Transient thermal and physiological responses were evaluated in semi-outdoor space.•Thermal responses stabilized within 1 min due to past thermal experiences.•Mean skin temperature and heart rate increased in semi-outdoor space.•Mean facial temperature was more thermally sensitive than that in the whole body.•Transient thermal and physiological responses were small in the tropics.