Outdoor thermal comfort requirements of Taiwanese and Hungarians in the warm months

Thermal conditions of an urban space, as well as the way how people perceive these conditions are highly relevant to their satisfaction and, as a consequence, they influence the patterns of area usage. In this paper we compare the thermal perceptions and thermal conditions related preferences of citizens (healthy adults) from two nations: the people in Central Taiwan (living under hot-humid subtropical climatic conditions) and the Hungarians living in Szeged (under cooler and drier climate). Using the databases of more field measurement campaigns carried out in the last 10 years (microclimatic measurements, questionnaire surveys as well as observations) we compare the thermal sensitivity of healthy adults in the warm seasons. In Taiwan it covers the months from March to November, while in Hungary it means the June–August period. Thermal conditions were expressed in terms of the Physiologically Equivalent Temperature (PET) index which incorporates the effect of air temperature, humidity, wind velocity and the mean radiant temperature (Tmrt) measured during the human monitoring. To overcome the problem of the differences in obtaining the Tmrt, namely the fact that the Taiwanese group used a standard globe thermometer, while the Hungarian researchers applied the six-directional pyranometer–pyrgeometer technique, we made preliminary corrections on the Taiwanese Tmrt database to eliminate the differences between the techniques. Subject's perception about the thermal conditions was recorded on a 7-degree scale in Taiwan (TSV – Thermal Sensation Vote; ranging from cold=-3 to hot=3 with a neutral=0) and on a 9-degree scale in Hungary (from very cold=-4 to very hot=4). To support the equal-based comparison, the Hungarian scale was converted into the same 7 categories. Preferences for changes in terms of the air temperature, sunshine and wind were measured on 3-degree scales in both nations. While the neutral temperature (Tn; the PET value at which the mean TSV=0) of the Taiwanese subjects (27.5°C) was considerably higher than that in Hungary (20°C), the difference between the preferred temperature (Tp; PET value at which the lowest proportion of subjects want cooler or warmer conditions) values was small (23.5°C and 26°C). While in Taiwan the neutrally perceived conditions were warmer than the preferred conditions (Tn>Tp), the situation was quite the opposite in Hungary (Tn < Tp). The neutral zone (the PET range when the mean TSV is between -0.5 and 0.5) was significantly wider in Taiwan (21–33.5°C) than that in Hungary (17–22.5°C), and the boundaries of the slightly warm and warm thermal sensation categories occurred at much higher PET values in Taiwan, showing the effect of adaptation to the hot conditions (both physiologically and psychologically). Not only the wider neutral zone indicated the increased tolerance of the Taiwanese people; but we discovered comparatively lower proportion of Hungarians who were satisfied with the thermal environment as it was. Namely, the ‘preferred' PET zone, where more than 50% of the questioned individuals wanted no change in terms of the temperature, was much wider in Taiwan (more than 15°C wide) than that in Hungary (only 3°C wide). Contrary to the thermal perception characteristics, and the width of the so-called preferred PET zone, we couldn't discover big differences between Taiwanese and Hungarian subjects in terms of their other thermal-comfort related preferences. More than half of the Taiwanese subjects wished for cooler conditions (lower temperature), less sunshine and stronger wind when the PET values exceeded the 34, 37 and 39°C, respectively. The corresponding ‘too hot PET benchmarks' of Hungarians were 32, 36 and 38.5°C.