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Line 20: − + − + − 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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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>.
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.
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.
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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{|class="wikitable"
|+ Considerations for using a 'high organic' planting medium
|+ 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
*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
*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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[[category:materials]]
[[category:materials]]
[[category:green infrastructure]]
[[category:green infrastructure]]