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Green roofs

Green infrastructure means introducing vegetation on/in man-made buildings and constructions to provide environmental, economic, and social benefits (i.e., clean air and water, climate regulation, food provision, erosion control, and places for recreation) [1]. Green roofs advantages over traditional solutions include reduction of surface runoff in large cities, reduced urban heat islands, support to biodiversity, improvement of the durability of waterproofing materials, increase of energy savings in buildings, and enhanced carbon sinking capacity [2]. 

Left: intensive green roof in Singapore; right: extensive green roof in Lleida (Spain) [2]

 

Green roofs are usually made of the following layers (from top to bottom): vegetation layer, substrate layer (usually topsoil or garden soil), filter layer (usually polypropylene or polyester geotextile membranes), drainage layer (being polyethylene or polystyrene modular panels, or porous stone materials with some retention capacity), protection layer, and root barrier and waterproofing layer [2,3]. 

 

Energy balance in a green roof system [1] 

 

Green roofs can be extensive or intensive. Extensive green roofs have a thin substrate layer, are light weight, do not feature irrigation systems, and are planted with resistant species. Intensive green roofs have larger substrate thicknesses, include an irrigation system, and the plant species used are those of typical traditional gardens. 

 

A careful selection of plants in view of the local climatic conditions, building characteristics, and type of system configuration is very important [3,4]. Selecting an appropriate type of plant will greatly affect the performance of the system because different types of plants have different characteristics, including plant trait, leaf area index, foliage height, albedo, and stomatal resistance. In addition to that, the selection of plants also depends on a few factors, such as preferred visual effect, availability of plant species, and requirement of an irrigation system. 

 

MATURITY:  

 

Green roofs are mature and in the market (TRL 8-9). Nevertheless, there is research going on to improve some of their components (TRL 3-6). 

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Authors

Resilient Network Cities
CEREMA
JRC

Tags

Climate resilienceGreen areasNature based solutionsBuilding
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