Changes

To maximize the utility of a green roof as a low impact development tool, coverage with planting should be maximized. In many cases this means only inaccessible spaces are used.

To maximize the utility of a green roof as a low impact development tool, coverage with planting should be maximized. In many cases this means only inaccessible spaces are used.

<h3>Amenity</h3>

===Amenity===

Roof gardens with a high proportion of impermeable surface are popular in high rise developments. These amenity terraces are often described as green roofs, but the LID benefit applies only to the vegetated areas. The stormwater benefit of all kinds of green roofs is maximized by combined with [[rainwater harvesting]] for subsequent irrigation. Sedum and native species have all been shown to thrive with daily irrigation to saturation<ref>http://grit.daniels.utoronto.ca/green_roof_image_index/#</ref>.

Roof gardens with a high proportion of impermeable surface are popular in high rise developments. These amenity terraces are often described as green roofs, but the LID benefit applies only to the vegetated areas. The stormwater benefit of all kinds of green roofs is maximized by combined with [[rainwater harvesting]] for subsequent irrigation. Sedum and native species have all been shown to thrive with daily irrigation to saturation<ref>http://grit.daniels.utoronto.ca/green_roof_image_index/#</ref>.

Rooftop farming is also becoming common in some Ontario cities. Again consideration should be given to the proportion of the roof actually planted. Where large open expanses of roof are being cropped, measures may be required to reduce erosion of exposed planting medium. Any digging or furrows will reduce the stormwater benefit.

Rooftop farming is also becoming common in some Ontario cities. Again consideration should be given to the proportion of the roof actually planted. Where large open expanses of roof are being cropped, measures may be required to reduce erosion of exposed planting medium. Any digging or furrows will reduce the stormwater benefit.

<h3>Biodiversity</h3>

===Biodiversity===

Biodiversity opportunities are optimized by planting a variety of species. General advice on this has been prepared by the City of Toronto<ref>https://www1.toronto.ca/City%20Of%20Toronto/City%20Planning/Zoning%20&%20Environment/Files/pdf/B/biodiversegreenroofs_2013.pdf</ref>. In the long term, the richness of species increases owing to 'volunteer species'. The desirability of this diversity varies with the aesthetic concerns of the green roof owner.

Biodiversity opportunities are optimized by planting a variety of species. General advice on this has been prepared by the City of Toronto<ref>https://www1.toronto.ca/City%20Of%20Toronto/City%20Planning/Zoning%20&%20Environment/Files/pdf/B/biodiversegreenroofs_2013.pdf</ref>. In the long term, the richness of species increases owing to 'volunteer species'. The desirability of this diversity varies with the aesthetic concerns of the green roof owner.

<h3>Design for Maintenance</h3>

===Design for Maintenance===

Detailed inspection and maintenance advice can be found in Sustainable Technologies' LID I&M guide <ref>http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2016/08/LID-IM-Guide-7.6-Green-Roofs.pdf</ref>.  

Detailed inspection and maintenance advice can be found in Sustainable Technologies' LID I&M guide <ref>http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2016/08/LID-IM-Guide-7.6-Green-Roofs.pdf</ref>.  

The primary operational concern for operating a green roof is the development of a leak. Green roofs protect the roof membrane from UV damage and should increase the lifespan of the roof. However, in the event that a leak is discovered a section of green roof would have to be removed for access. Some proprietary systems appear to be easier to remove and replace. This may come at a cost, as the rainwater retention of the system is somewhat reliant on continuous coverage of the green roof surface.

The primary operational concern for operating a green roof is the development of a leak. Green roofs protect the roof membrane from UV damage and should increase the lifespan of the roof. However, in the event that a leak is discovered a section of green roof would have to be removed for access. Some proprietary systems appear to be easier to remove and replace. This may come at a cost, as the rainwater retention of the system is somewhat reliant on continuous coverage of the green roof surface.

<p>Green roofs should receive as little maintenance as possible. Regular inspection is only required to see that the drains are free from obstruction and that the vegetation coverage is adequate to prevent wind erosion. During detailed design, all areas adjacent to the green roof itself should be kept free from granular material. Sediment accumulates in  gravel edging, which then permits the vegetation to take root and spread.

 

Green roofs should receive as little maintenance as possible. Regular inspection is only required to see that the drains are free from obstruction and that the vegetation coverage is adequate to prevent wind erosion. During detailed design, all areas adjacent to the green roof itself should be kept free from granular material. Sediment accumulates in  gravel edging, which then permits the vegetation to take root and spread.

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The [[Geotextiles| geotextile]] layer is included to prevent migration of the planting medium into the drainage layer.  Current advice is to specify a free draining textile to prevent potential water-logging of the planting medium. Observations green roof assemblies have shown a reduction of flow from specifications owing to interactions of medium particles with the textile.

The [[Geotextiles| geotextile]] layer is included to prevent migration of the planting medium into the drainage layer.  Current advice is to specify a free draining textile to prevent potential water-logging of the planting medium. Observations green roof assemblies have shown a reduction of flow from specifications owing to interactions of medium particles with the textile.

<h3>Planting Medium</h3>

===Planting Medium===

{{:Green_roof_media}}

{{:Green_roof_media}}

<h3>Irrigation</h3>

===Irrigation===

Regular irrigation has been shown to substantially reduce the stormwater capture benefit of an extensive green roof<ref name=Hill/>.   

Regular irrigation has been shown to substantially reduce the stormwater capture benefit of an extensive green roof<ref name=Hill/>.   

One way to reduce the irrigation used on green roofs is through the use of smart technologies. Responsive sensors that suppress irrigation after a rainstorm are routinely attached to green roofs to conserve water. Improvements can be made by instead using a 'soil' moisture sensor to trigger irrigation. State-of-the-art management systems now use predicted weather data to suppress irrigation ahead of storm events, see [[digital technologies]].   

One way to reduce the irrigation used on green roofs is through the use of smart technologies. Responsive sensors that suppress irrigation after a rainstorm are routinely attached to green roofs to conserve water. Improvements can be made by instead using a 'soil' moisture sensor to trigger irrigation. State-of-the-art management systems now use predicted weather data to suppress irrigation ahead of storm events, see [[digital technologies]].   

Maximizing evaporation with spray irrigation is the faster way to empty a stormwater cistern, and provides some cooling benefit for the building and it's surroundings.

Maximizing evaporation with spray irrigation is the faster way to empty a stormwater cistern, and provides some cooling benefit for the building and it's surroundings.

<h3>Planting</h3>

===Planting===

The choice of vegetation on an extensive green roof is insignificant in stormwater management compared to the choice of planting medium or the provision of irrigation. The vegetation should be selected to be resilient to both very wet and very dry periods.''Sedum'' species are the most common choice, demonstrating excellent longevity in systems with or without irrigation.  

The choice of vegetation on an extensive green roof is insignificant in stormwater management compared to the choice of planting medium or the provision of irrigation. The vegetation should be selected to be resilient to both very wet and very dry periods.''Sedum'' species are the most common choice, demonstrating excellent longevity in systems with or without irrigation.  

Some projects expect the low growing <em>Sedum</em> to  remain in graphic designs according to species and flower color. This is not a realistic expectation without significant maintenance costs. Instead project stakeholders should be prepared early in the design process to embrace the green roof as a living and evolving ecosystem. Designs which incorporate both ''Sedum'' and native species can help with this.

Some projects expect the low growing ''Sedum'' to  remain in graphic designs according to species and flower color. This is not a realistic expectation without significant maintenance costs. Instead project stakeholders should be prepared early in the design process to embrace the green roof as a living and evolving ecosystem. Designs which incorporate both ''Sedum'' and native species can help with this.

See: [[Planting for Green Roofs]]

See: [[Planting for Green Roofs]]

<h3> Drains and Vegetation Free zones </h3>

===Drains and Vegetation Free zones===

Vegetation free areas are often required around the perimeter of the roof to reduce wind uplift, on larger areas requiring firebreaks, for access paths and around drains.  To prevent accumulation of sediment and migration of the vegetation, the vegetation free areas should not be filled with decorative aggregate or river rock.  Instead concrete pavers or other surfaces that do not actively trap particles will reduce weeding maintenance.

Vegetation free areas are often required around the perimeter of the roof to reduce wind uplift, on larger areas requiring firebreaks, for access paths and around drains.  To prevent accumulation of sediment and migration of the vegetation, the vegetation free areas should not be filled with decorative aggregate or river rock.  Instead concrete pavers or other surfaces that do not actively trap particles will reduce weeding maintenance.