綠屋頂具有調節都市水文、減少建築物能源使用、改善空氣品質與暴雨水質、減少噪音、提供生態棲地、美化景觀等環境效益與功能。綠屋頂利用既有空間，不需要土地成本，被認為是建造生態城市與永續城市的重要方法。國內的綠屋頂實施案例不斷增加中，台北市與新北市政府更有專案以市容美觀、建構低碳城市為目的，獎勵與補助民眾設置綠屋頂。然而除了溫度的監測與研究外，國內少有其他綠屋頂環境品質的監測與探討。總合國外文獻與國內實測結果，綠屋頂的水質汙染濃度通常比一般屋頂要高，雖然綠屋頂能夠減少總逕流量，使總污染輸出量降低，但仍顯示若綠屋頂操作不當，反而可能成為都市的潛在污染源。生長基層與植栽種類為影響綠屋頂水質的主要因素，生長基層透過過濾減少污染，植物亦能吸收有機物質，理論上有改善水質效能。但降雨後，植物與土壤層有機物可能被沖刷流出，造成水質中的營養鹽與沉積物濃度反而提高。因此本計畫進行實驗模組設計，以不同生長基層成份與厚度，搭配三種常見但特性不同的綠屋頂植物：台北草、佛甲草以及虎尾蘭，採取自然降雨水樣，觀察植栽生長情況，並分析生長基層與植栽對於綠屋頂水質的影響。本研究成果可作為未來推廣綠屋頂的設計原則與重要參考。
Green roofs have the advantages of adjusting urban hydrology, saving buildings energy, improving air quality and stormwater quality, moderating noise, providing ecologic habitats, aesthetic and recreation values. In addition, due to not require extra land space and no land cost the green roofs are preferred for eco-city or sustainable city development. The setting of green roofs in Taiwan is increasing dramatically in recent years. The government of Taipei city and New Taipei city provide subsidies to encourage citizens to build up green roofs. However, the local monitoring and studies were focus on temperature decreasing and very few emphasized other environmental benefits gained by green roofs. According to the international experiences and local monitoring data, the water quality in green roofs is usually worse than in traditional roofs. Although the green roofs is able to reduce the total runoff quantity and decrease the total loadings of pollutants, without proper design and management it is very likely becoming a pollution source of urban stromwater. Growing substrates and plant species are the two important factors effecting water quality of green roofs. The growing substrate can filter and retain pollutant and the plants can filter and absorb organic substances. However, the plants and soil might be washout by storm and result in high concentration of nutrient and sediment in runoff. Therefore, the proper usage of growing substrate and plants is very crucial to the performance of a green roof. This study will design several experiment modules with diffidence substrate contents and substrate depths, combing three local green roof plant species, which are Zoysia matrella, Sedum mexicanum, and Sansevieria trifasciata. The water quality will be sampled and analyzed to identify the effects of substrate and plants species. The effects of substrate on plants will also be recorded. This study is aimed to provide local monitoring data on water quality of green roofs and suggest the design principles of growing substrate and plant species to avoid pollution production.
