How "green" are the green roofs? Lifecycle analysis of green roof materials

Green roofs can be classified as intensive and extensive roofs based on their purpose and characteristics. Green roofs are built with different layers and variable thicknesses depending on the roof type and/or weather conditions. Basic layers, from bottom to top, of green roof systems usually consists of a root barrier, drainage, filter, growing medium, and vegetation layer. There are many environmental and operational benefits of vegetated roofs. New technology enabled the use of low density polyethylene and polypropylene (polymers) materials with reduced weight on green roofs. This paper evaluates the environmental benefits of green roofs by comparing emissions of NO2, SO2, O-3 and PM10 in green roof material manufacturing process, such as polymers, with the green roof's pollution removal capacity. The analysis demonstrated that green roofs are sustainable products in long-term basis. In general, air pollution due to the polymer production process can be balanced by green roofs in 13-32 years. However, the manufacturing process of low density polyethylene and polypropylene has many other negative impacts to the environment than air pollution. It was evident that the current green roof materials needed to be replaced by more environmentally friendly and sustainable products. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.

根据其用途和特点，绿色屋顶可分为集约型和粗放型屋顶。绿色屋顶依据屋顶类型和/或天气条件，由不同的层次和不同的厚度构成。绿色屋顶系统从底部到顶部的基本层次通常包括隔根层、排水层、过滤层、种植介质层和植被层。植被屋顶有许多环境和使用方面的益处。新技术使得在绿色屋顶上能够使用重量减轻的低密度聚乙烯和聚丙烯（聚合物）材料。本文通过比较绿色屋顶材料制造过程（如聚合物）中二氧化氮、二氧化硫、臭氧和可吸入颗粒物（PM10）的排放与绿色屋顶的污染去除能力，来评估绿色屋顶的环境效益。分析表明，从长期来看绿色屋顶是可持续的产品。一般来说，聚合物生产过程造成的空气污染可在13 - 32年内被绿色屋顶平衡。然而，低密度聚乙烯和聚丙烯的制造过程除了空气污染外，对环境还有许多其他负面影响。很明显，当前的绿色屋顶材料需要被更环保和可持续的产品所替代。版权归英国皇家所有（C）2011，由爱思唯尔有限公司出版。保留所有权利。