綠屋頂生命週期與成本效益評估方法比較分析

Abstract

綠屋頂(GRs)由於具有多重效益，國內外均已在推廣中，本研究群亦已開發了水盆式輕空透氣型綠屋頂(LHVGR)及DIY式綠屋頂(DGR)，然而目前並未針對各式綠屋頂作過較完整比較分析，本研究因而針對各式綠屋頂進行生命週期評估(LCA)及成本與效益綜合分析。 目前LCA已有各種中間點及終點方法可供使用，但各方法都不盡相同，所得結果也會有差異及影響後續的評估，故本研究比較分析各項中間點方法間之差異，並分析其對本研究之適用性，且進行綜合比較分析，亦分析各綠屋頂之成本效益及其城市規模效益，最後就環境衝擊、潛在危害、成本及各項效益進行綜合分析，以期對各式綠屋頂作較完整的分析比較。 中間點以Impact 2002+、BEES+和CML-IA(Baseline)三種方法進行比較。全球暖化評估結果，三種方法皆以DGR-100對環境的影響較大；自然資源消耗則以LHVGR影響最大；生態毒性及臭氧層破壞評估下，三種方法均以GR衝擊值較大；優養化與酸化則以LHVGR、DGR-100、DGR-64為主要環境衝擊的綠屋頂；至於人體健康致癌毒性方面，三種方法的LHVGR、DGR-100與DGR-64綠屋頂對環境衝擊差異並不大，略為相似。 Impact 2002+與EPS 2000為本研究採用的終點整合方法，結果顯示，Impact 2002+方法之Resources與EPS 2000的Abiotic Stock Resource，其衝擊量分別占了各損害類別項目之50%及75%以上，乃因各綠屋頂使用一些人造材料或物料，使Resources和Abiotic Stock Resource衝擊比例相對較高，故若要改善綠屋頂對於環境的衝擊，應儘可能避免採用人造材料。 成本與各項效益評估方面，若以四十年之年均成本計算，裸屋頂上方建置綠屋頂，其GR所花的經費較高，LHVGR則最低，綠覆率以取代台北草及假儉草計算約可減少9.6與12.6元/m2投資；減緩熱島效應評估方面，假若新竹市90%建置綠屋頂，且以全市6-9月為主要效益，其總減碳量約為32.78千噸CO2eq/yr；節能方面，以LHVGR有較大的節能效益，約為4.80~5.18 kWh/m2/year及雨水回收率。

Since green roofs (GRs) can offer various benefits, domestic and foreign cities had widely applied GRs. This research group had also developed several light and hollow ventilated green roofs (LHVGRs) and DIY green roofs (DGRs). However, so far no comprehensive analysis is available for comparing these GRs. This study thus will implement life cycle assessment (LCA) and cost-benefit analyses for comparing the conventional roof (CR), GR, LHVGR, and DGR. There exist different LCA midpoint and endpoint methods that may give different impact valuations and may subsequently affect the final assessment. This study thus will evaluate the results obtained from varied methods and analyze their applicability for comparing life cycle environmental impacts of different green roofs. Personnel and city-wide costs and benefits of different green roofs will be also estimated. A comprehensive aggregative analysis based on aforementioned results will be implemented to compare the green roofs. This study selects Impact 2002+, BEES+ and CML-IA(Baseline) three midpoint methods to compare and analyze their results for assessing various GRs. Among Global warming assessment results, DGR-100 has greatest impact evaluated by all three methods. LHVGR ranks the worst for Natural resource depletion, while GR does not perform well for Ozone layer depletion and Ecotoxicity. LHVGR, DGR-100 and DGR-64 all have significant impacts on Eutrophication and Acidification. The Human cancer toxicity impacts of LHVGR,DGR-100 and DGR-64 are similar. Two endpoint methods of Impact 2002+ and EPS 2000 are also evaluated. The results show that Resources and Abiotic Stock Resource respectively contribute 50% and 75% of the endpoint scores, because green roofs use several artificial materials that increase the impacts on Resources and Abiotic Stock Resource. Therefore, the effective approach for reducing the impacts from green roofs, is to avoid using artificial materials. Personnel and city-wide cost and benefit assessments, in terms of the average annual cost of forty years, are also implemented. GR have higher initial cost than LHVGR. With the green cover ratio policy, GRs can replace grass investment for about 9.6 to 12.6NT$/m2. The carbon emission reduction is about 32.78 kiloton CO2eq/yr. LHVGR performs the best in energy saving, saving approximately 4.80~5.18 kWh/m2/year. In addition, LHVGR also performs the best in rainwater recovery.