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The green roof media used in Ontario can be classed according to proportion of composted biological material. Some existing installations use materials which comply with FLL guidelines, whilst others use a much higher proportion of [[compost]]<ref>Hill, J., Drake, J., and Sleep, B. (2016). “Comparisons of extensive green roof media in Southern Ontario.” Ecological Engineering, Elsevier B.V., 94, 418–426.</ref>.  
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The [[green roofs|green roof]] media used in Ontario can be classed according to proportion of composted biological material. Some existing installations use materials which comply with FLL guidelines, whilst others use a much higher proportion of [[compost]]<ref>Hill, J., Drake, J., and Sleep, B. (2016). “Comparisons of extensive green roof media in Southern Ontario.” Ecological Engineering, Elsevier B.V., 94, 418–426. https://www.sciencedirect.com/science/article/abs/pii/S0925857416302804?via%3Dihub</ref>.  
    
ASTM International have a number of standards relating to various design considerations for green roofs. These standards provide good technical advice on the testing of systems and components.
 
ASTM International have a number of standards relating to various design considerations for green roofs. These standards provide good technical advice on the testing of systems and components.
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In many proprietary systems the default option for planting medium will be a granular material with very low organic matter content. However, many companies can arrange for a high [[organic matter]] alternative to be substituted if requested.   
 
In many proprietary systems the default option for planting medium will be a granular material with very low organic matter content. However, many companies can arrange for a high [[organic matter]] alternative to be substituted if requested.   
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Increasing the depth of planting medium from 10 cm to 15 cm has been shown to benefit the vegetation <ref>MacIvor JS, Margolis L, Puncher CL, Carver Matthews BJ. Decoupling factors affecting plant diversity and cover on extensive green roofs. J Environ Manage. 2013;130:297-305. https://www.sciencedirect.com/science/article/abs/pii/S0301479713006051?via%3Dihub</ref>, however stormwater retention was not improved with this increase in depth <ref>Hill, J., Drake, A. P. J., Sleep, B., and Margolis, L. (2017). “Influences of Four Extensive Green Roof Design Variables on Stormwater Hydrology.” Journal of Hydrologic Engineering. https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29HE.1943-5584.0001534</ref>
    
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|+ Considerations for using a 'high organic' planting medium
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|+ Considerations for using a 'high organic', [[compost]] based planting medium
 
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!Benefits
 
!Benefits
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*Increased water holding capacity, which benefits both vegetation health and stormwater retention  
 
*Increased water holding capacity, which benefits both vegetation health and stormwater retention  
*Often lighter weight, even when saturated
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*Lighter weight, even when saturated
 
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*Increased [[phosphorus]] concentration in runoff water, however this may be mitigated by the reduced runoff volume resulting in a lower loading overall
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*Increased [[phosphorus]] concentration in runoff water.
 
*The lightweight material is more prone to wind erosion, and this should be accounted for in the initial design, alternatives include erosion control blankets, soil tackifiers, or Sedum mats.
 
*The lightweight material is more prone to wind erosion, and this should be accounted for in the initial design, alternatives include erosion control blankets, soil tackifiers, or Sedum mats.
 
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Increasing the depth of planting medium from 10 cm to 15 cm has been shown to benefit the vegetation <ref>MacIvor JS, Margolis L, Puncher CL, Carver Matthews BJ. Decoupling factors affecting plant diversity and cover on extensive green roofs. J Environ Manage. 2013;130:297-305. doi:10.1016/j.jenvman.2013.09.014.</ref>; stormwater retention was not improved with this increase in depth <ref>Hill, J., Drake, A. P. J., Sleep, B., and Margolis, L. (2017). “Influences of Four Extensive Green Roof Design Variables on Stormwater Hydrology.” Journal of Hydrologic Engineering.</ref>
   
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[[category:materials]]
 
[[category:materials]]
 
[[category:green infrastructure]]
 
[[category:green infrastructure]]

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