人行步道空間的陰影連續性設計與熱舒適評價

Design of Shadow Continuity and Assessment of Thermal Comfort for Pedestrian Areas

人口成長導致都市發展規模的持續擴張、人工材質與排熱量增加，使都市熱島現象日漸嚴重，減緩都市熱島效應的手法與對策成為近年備受重視的議題。藉由陰影增加改善人體舒適度（thermal comfort）是有效的策略之一，本研究以「溫熱環境」的觀點，利用陰影降低平均輻射溫度MRT的策略，增加戶外步行空間陰影的覆蓋，改善人體熱舒適品質。本研究選定台南市海安路的人行步道作為研究區域，對進行夏季期間8:00~17:00共三時段的CFD （computational fluid dynamics）陰影模擬，以「陰影堆疊地圖」為基礎，建立「陰影覆蓋比率評估法」及「熱舒適指標評估法」分析陰影分布與熱舒適度。其中，陰影覆蓋比率評估法以陰影評分（空間連續性）與權重評分（時間連續性）檢討陰影分布情形，而熱舒適指標評估法為利用人體熱舒適評估指標SET*評估人體熱舒適度。除現況（case 0）的討論外也提出設置「遮棚改善方案」（case 1）、植栽改善方案：「小型植栽改善方案」（case 2-1）、「中型植栽改善方案」（case 2-2）探討各方案的改善效益。遮棚的設置可改善上午及下午時段單側的熱舒適度，而植栽的熱舒適度改善雖較不顯著，但中型植栽的行道樹設置則可創造出東西兩側步道平均較佳的步行空間環境，至於小型植栽的行道樹設置對於中午時段的熱舒適改善效益則較小。

The urban heat island effect has worsened because of rapid population growth resulting in urban expansion, large heat rejection, and increased use of construction materials. Methods and strategies for alleviating the urban heat island effect thus are important. Increasing shaded areas is considered one of the most efficient strategies for improving human thermal comfort. This study uses the improvement of thermal environment and human thermal comfort to increase shaded areas in outdoor pedestrian spaces to reduce mean radiant temperature (MRT). Selects Hai’an Road in Tainan City as its research area, and simulates the shaded area of the pedestrian space in summer from 8:00 to 17:00 using CFD (computational fluid dynamics) models. Based on the Shadow Superimposition Map, the Shadow Coverage Assessment and Thermal Comfort Assessment are established for evaluating shading distribution and thermal comfort. The former uses shading assessment and weighted mean assessment to assess the spatial and temporal contiguity, while the latter uses SET* to assess the effect of shade on human thermal comfort. Besides examining the current situation (case 0), this study proposes short-term strategies for improving human thermal comfort. These strategies include setting building shelters (case 1), planting small arbores (case 2-1), and planting medium arbores (case 2-2). The installation of shelters is found to perform better in improving thermal comfort on one side in the morning and afternoon, respectively. Meanwhile, planting is less effective in improving thermal comfort. However the planting of medium arbores provides a better walking space on both the east and west sidewalks, while planting of small arbores is of less benefit in improving thermal comfort.