Changes

*“Minimum” and “High” life cycle costs estimates are based on two different types of extensive green roof systems; a low cost 10 cm deep without irrigation and water-proofing membrane design and a higher cost 15 cm deep with irrigation and membrane design. For a detailed description of construction, inspection, maintenance and rehabilitation cost assumptions see section 7.1.7 of the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf LID Stormwater Management Practice Inspection and Maintenance Guide].

*“Minimum” and “High” life cycle costs estimates are based on two different types of extensive green roof systems; a low cost 10 cm deep without irrigation and water-proofing membrane design and a higher cost 15 cm deep with irrigation and membrane design. For a detailed description of construction, inspection, maintenance and rehabilitation cost assumptions see section 7.1.7 of the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf LID Stormwater Management Practice Inspection and Maintenance Guide].

*For all scenarios, the CDA (i.e., green roof area) is 2,000 m² and cost estimates include crane mobilization and demobilization to install, deconstruct and reconstruct the green roof. The 10 cm deep growing media bed is planted with cuttings and the “with water-proofing membrane” design is installed with a thermoplastic polyolefin (TPO) membrane and no membrane leak detection system. The 15 cm deep growing media bed is planted with pre-grown sedum mats, includes an irrigation system, and the “with waterproof membrane” design is installed with a synthetic rubber, ethylene propylene diene terpolymer (EPDM) membrane and an Electric Field Vector Mapping (EFVM) leak detection system.  

*For all scenarios, the CDA (i.e., green roof area) is 2,000 m² and cost estimates include crane mobilization and demobilization to install, deconstruct and reconstruct the green roof. The 10 cm deep growing media bed is planted with cuttings and the “with water-proofing membrane” design is installed with a thermoplastic polyolefin (TPO) membrane and no membrane leak detection system. The 15 cm deep growing media bed is planted with pre-grown sedum mats, includes an irrigation system, and the “with waterproof membrane” design is installed with a synthetic rubber, ethylene propylene diene terpolymer (EPDM) membrane and an Electric Field Vector Mapping (EFVM) leak detection system.  

*Estimates of the life cycle costs for all green roof design variations and maintenance scenarios in Canadian dollars per unit CDA ($/m²) are presented in the table below. [[LID Life Cycle Costing Tool]] allows users to select what BMP type and design variation applies, and to use the default assumptions to generate planning level cost estimates.

*Estimates of the life cycle costs for all green roof design variations and maintenance scenarios in Canadian dollars per unit CDA ($/m²) are presented in the table below. [[Cost analysis resources|LID Life Cycle Costing Tool]] allows users to select what BMP type and design variation applies, and to use the default assumptions to generate planning level cost estimates.

*For all BMP design variations and maintenance scenarios, it is assumed that replacement of the waterproofing membrane is needed at 40 years of age (TRCA & U of T, 2013a<ref>Toronto and Region Conservation Authority and University of Toronto (TRCA & U of T). 2013. Assessment of Life Cycle Costs for Low Impact Development Stormwater Management Practices. Toronto, ON</ref>). Where a green roof is in place, replacement of the water-proofing membrane is assumed to typically involve the following tasks and associated costs:

*For all BMP design variations and maintenance scenarios, it is assumed that replacement of the waterproofing membrane is needed at 40 years of age (TRCA & U of T, 2013<ref>Toronto and Region Conservation Authority and University of Toronto (TRCA & U of T). 2013. Assessment of Life Cycle Costs for Low Impact Development Stormwater Management Practices. Toronto, ON</ref>). Where a green roof is in place, replacement of the water-proofing membrane is assumed to typically involve the following tasks and associated costs:

**Deconstruction of all green roof components and layers;

**Deconstruction of all green roof components and layers;

**For 10 cm growing media bed designs, harvesting 2/3 of the plant material needed to replant by cuttings;

**For 10 cm growing media bed designs, harvesting 2/3 of the plant material needed to replant by cuttings;

#Maintenance and rehabilitation costs over a 50 year time period for the Minimum Frequency maintenance scenario are estimated to be 2.04 and 1.48 times the original construction costs for the 10 cm and 15 cm with membrane designs, respectively.  

#Maintenance and rehabilitation costs over a 50 year time period for the Minimum Frequency maintenance scenario are estimated to be 2.04 and 1.48 times the original construction costs for the 10 cm and 15 cm with membrane designs, respectively.  

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