熱季街道環境與熱舒適性關係之研究

Street Environment and Thermal Comfort in Hot Season

人體熱舒適性會受到很多面向因素的影響，例如：人體生理機能、熱感受度、衣著量、溫度、濕度、風速…等。本研究為釐清都市街道環境對於熱舒適性之影響，於街道五處不同環境條件之位置，連續三日測量各項熱舒適相關數據（上午11時到深夜22時），並且計算其「綜合溫度熱指數」（The Wet Bulb Globe Temperature, WBGT）及「平均輻射溫度」（Mean Radiant Temperature, MRT），藉此對未來街道環境與熱舒適性改善提出實質建議。經本研究實測與分析後發現，都市街道中之熱環境與熱舒適度受到建築陰影、植栽陰影、建築與鋪面材料、通風條件、環境濕度、日照條件等因素所影響，進而反應在乾球溫度、濕球溫度、相對濕度、平均風速、黑球溫度等實測數據上。在五個實測點中，有兩個位於遮蔭條件較佳的實測點擁有較好的熱環境與熱舒適性。此外，有一處位於園道旁的實測點，固然擁有良好的通風環境與植栽蒸散冷卻優勢，但因沒有較好的遮蔭條件，故在乾球溫度、輻射（黑球）溫度、WBGT及MRT數值上顯得與街道中的量測點差異無幾。因此，相較於通風與植栽蒸散降溫作用，製造陰影對於改善熱環境與熱舒適性而言，誠是更重要的策略。根據本研究實測結果與分析，建議未來應該增加都市街道之遮蔽條件，且由於植栽兼具遮蔭效果及蒸發散降溫之效益，對熱環境改善及熱舒適性的提升頗有顯著貢獻，故除了促使街邊建築物為都市街道創造更多遮蔭範圍外，更推薦以園道、行道樹及街道綠化等手法強化街道遮蔭條件。總之，透過本研究建議之街道環境控制方法，不但可以改善街道熱舒適性，更可以有助於降低空調能源消耗與碳排放量，達到節能減碳的目標。

Human thermal comfort is affected by factors such human physiology, thermal perception of clothing amount, temperature, humidity and wind speed. This study collected data from five measuring stations on the same street but in different environmental conditions from 11 am to 22 pm on September 3rd, 4th and 5th in 2011. The data were used to calculate WBGT (Wet Bulb Globe Temperature) and MRT (Mean Radiant Temperature) index, to clarify the thermal comfort affected by the urban street environment, and to provide recommendations to the street environment and thermal comfort improvement. The measurement and analysis results showed that that the thermal comfort and thermal environment of city streets was affected by building shadow, planting shadows, architectural and pavement material, ventilation, humidity, sunlight conditions, meanwhile, reacted in dry bulb temperature(air temperature), wet bulb temperature, relative humidity, the average wind speed, globe temperature and other measured data. Of these five measuring points, two had better thermal comfort and thermal environment due to their better shading environment. Moreover, one measuring point near the green corridor had a higher air temperature, globe temperature, WBGT and MRT as well as the measuring points on the street even though it has good ventilation and evapotranspiration cooling conditions, because it don’t have nice shading. These data show that, for improving the thermal environment and thermal comfort, providing shade is a much better strategy than providing ventilation or cooling through evapotranspiration. In contrast, radiation temperature is a key factor in WBGT. Analyses of data for these measurement points show that areas that are shaded (covered by the shadows of buildings or trees) have lower radiation temperature. Therefore, this study suggests that shaded areas in urban streets should be increased for mitigating urban warming and heat island effect. Therefore, applying the proposed methods of controlling the street environment can not only improve the thermal comfort of streets, but also reduce air conditioner energy consumption and carbon emissions to achieve targets of carbon reduction.