Supporting producers in designing more efficient and low-impact green roofs through the Life Cycle Analysis: environmental and energy performance

The environmental performance of six green roof solutions currently available on the Italian market has been compared and a lack of information comes out, both on environmental and thermal issues that are necessary to run a consistent and specific assessment. Life Cycle Analysis (LCA) could support producers in designing more efficient and low-impact green roofs, selecting materials based on their environmental profile over their life cycle and taking into account potential reuse of recycle at the end of life. This paper presents an environmental assessment 'cradle to gate', based on a 1-m2 functional unit (FU), according to European Standard EN 15804:2012+A1:2013. Five different scenarios, based on different “U-value” limits according to D.M. 26/06/2016, have been defined to run the comparison. Outcomes are expressed in parameters describing environmental impact and resources use. The results show that, despite a large interest in green roofs, currently considered to be a sustainable and energy saving solution for both cold and warm climate, no specific information and data are in fact available for designers and LCA practitioners to assess the environmental and energy performance accurately. Moreover, the insulation layer is the primary responsible for both the energy and environmental performance of the green roof and therefore, taking into account the LCA profile of the insulation material during the design stage is a crucial step to guarantee a low-impact building. Moreover, the new vegetative substrates available on the market are generally presented as more sustainable when, in fact, LCA quarrels with that. Therefore, a comparison between 7 different media currently available on the market has been carried out; results have been significantly affected by a large lack of specific LCI data.