Changes

==Overview==

==Overview==

[[Green Roofs]] consist of a layer of [[Green roofs: Planting|vegetation]] and [[Green roof media|planting medium]] installed on top of a [[Green roof construction|conventional flat or sloped roof]]. Green roofs are touted for their environmental benefits as they improve energy efficiency, reduce urban heat island effects and create greenspace for passive recreation and aesthetic enjoyment. They are also desirable for their water quality, water balance and peak flow control benefits. The green roof acts like a lawn or meadow by temporarily storing rainwater in the planting medium and ponding areas. Excess rainfall enters [[underdrains]] and [[overflow]] points and is conveyed to a storm sewer or other stormwater practice in the building drainage system. After a storm, a large portion of the stored water is evapo-transpired by the [[plants]], evaporated or slowly drains away. STEP has prepared life cycle costs estimates for each design configuration, based on a 2,000 m² road drainage area, runoff control target of 25 mm depth and 72 hour drainage period, for comparison which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated [https://sustainabletechnologies.ca/lid-lcct/ LID Life Cycle Costing Tool (LCCT) here].

[[Green Roofs]] consist of a layer of [[Green roofs: Planting|vegetation]] and [[Green roof media|planting medium]] installed on top of a [[Green roof construction|conventional flat or sloped roof]]. Green roofs are touted for their environmental benefits as they improve energy efficiency, reduce urban heat island effects and create greenspace for passive recreation and aesthetic enjoyment. They are also desirable for their water quality, water balance and peak flow control benefits. The green roof acts like a lawn or meadow by temporarily storing rainwater in the planting medium and ponding areas. Excess rainfall enters [[underdrains]] and [[overflow]] points and is conveyed to a storm sewer or other stormwater practice in the building drainage system. After a storm, a large portion of the stored water is evapo-transpired by the [[plants]], evaporated or slowly drains away. STEP has prepared a life cycle cost estimate for an extensive, 4 inch deep pre-grown sedum mat, green roof design configuration, based on a 2,000 m² roof drainage area, runoff control target of 25 mm depth, for comparison which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated [https://sustainabletechnologies.ca/lid-lcct/ LID Life Cycle Costing Tool (LCCT) here].

==Design Assumptions==

==Design Assumptions==

Green roofs are an ideal technology for sites without significant space at ground level for [[infiltration]] and zero-lot line projects with outdoor amenity requirements. Green roofs are typically [[Green roof construction|sized]] based on the available roof area, as opposed to treatment volume requirements. Green roofs are physically feasible in most development situations, but should be planned at the time of building design. <br>

Green roofs are an ideal technology for sites without significant space at ground level for [[infiltration]] and zero-lot line projects with outdoor amenity requirements. Green roofs are typically [[Green roof construction|sized]] based on the available roof area, as opposed to treatment volume requirements. Green roofs are feasible in most greenfield development situations, but should be planned at the time of building design. <br>

Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:

Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:

* Native soil infiltration rates for Full, Partial and No Infiltration Design scenarios were assumed to be 20 mm/h, 10 mm/h and 2 mm/h, respectively, and a safety factor of 2.5 (where applicable) was applied to calculate the design infiltration rate.  

* Building height between 1 and 5 stories.

* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, watering, weeding, removal of litter, plant replacement and removal of weeds (where applicable). Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ surface infiltration rate testing (where applicable)

* Roof length and width of 46.05 metres each, and slope of 2%.

* Irrigation and leak detection systems are not included.

* Designed to capture precipitation falling directly onto the roof surface, not to receive runoff diverted from other source areas.

* Growing medium depth of 4 inches.

* Plants consist of pre-grown sedum mats.

* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, and watering six times a year. Verification inspections are included every 5 years to confirm adequate maintenance.

===Notes===

===Notes===

* The tool calculates costs for new (greenfield) development contexts and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal.  

* The tool calculates costs for new (greenfield) development contexts and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal.  

** Land value and equipment mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction.

** Land value and equipment mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction.