Environmental performance of recycled rubber as drainage layer in extensive green roofs.

Posted by Maïté Thirouin
Full LCA available on the web
Publication year: 
recycled rubber as drainage layer in green roofs
Quality and sources
Is the study a: 
Detailed LCA
Was a critical review performed?: 
Is the study compliant with ISO 14044?: 
Sponsor name(s): 
Spanish Government
Sponsor name(s): 
European Union
Sponsor type: 
Public administration
Lidia Rincon
Julia Coma
Gabriel Perez
Albert Castell
Dieter Boer
Luisa F. Cabeza
Practitioner(s) type: 
Institut/Technical research center
Functional unit: 
9 m² of roofing system to cover a net floor area of 5,76m²
Goal and scope of the summary: 
The study aims to provide a comparative life cycle assessment of four roof systems. Two are extensive green roofs with different drainage layer: one in pozzolana stone and the other in rubber crumbs from used tire waste. The other two are flat conventional roofs: one is insulated by a classic layer of gravels and the other is not insulated. Contrary to previous studies, the present one is based on measures from an experimentation in real winter and summer conditions. Four house-like cubicles were built with the same internal dimensions. Each one has a different roof from the types cited above. The experiment takes place in the countryside of Spain with a Mediterranean continental climate. It lasted one year. The expected life time of the building and the roof is of 50 years. The electricity mix used is the one of the Spanish energy production system. Four life cycle stages are considered: production, construction, operational and disposal. Data on rubber crumbs were provided by a supplier company of tires. Data for standard materials were obtained in the EcoInvent database. Rubber crumbs come from local workshops whereas pozzolana gravels come from the Canary Islands. Besides, a distance of 100 km was assumed for the transport from production to the construction site of the rest of the materials. For the disposal stage, it was considered that all materials were disposed in inert materials landfills except for steel and rubber that were considered to be recycled and the asphalt membrane disposed in sanitary landfills. Impacts were evaluated using the EI99 aggregated indicator.

In conclusion, the study shows that extensive green roof with recycled rubber has a significant lower environmental impact compared to the pozzolana green roof or the non-insulated roof. However, its total environmental impact is similar to the conventional insulated roof.

The extensive green roof with recycled rubber presents the largest environmental impact for the production phase. For all roofs, the operational phase is crucial in the overall impact.
The green roof with recycled rubber crumbs allows great energy savings during the cooling period (summer).

There are other advantages of using of a green roof with recycled rubber. First of all, plenty of rubber tires are not recycled today. Also, it is a material available locally avoiding high transport costs. Finally, results of the study don't show the potential CO2 emissions reduction due to carbon fixed by plants. Especially if the system is installed in cities. 

Material impact(s): 
Ozone layer depletion
Water consumption
Global warming
Toxicity / Eco-toxicity
Raw material impact level: 
Manufacturing impact level: 
Shipping impact level: 
Usage impact level: 
End of life impact level: 

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