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===Overview===

==Overview==

<p>Modern green roofs are a rapidly developing  commercial market in Ontario. Their primary benefit as a LID technology is in maximizing evapotranspiration for water balance targets. </p>

<p> Green roofs are sometimes referred to as 'ecoroofs', 'vegetated roofs', 'living roofs'.</p>

Modern green roofs are a rapidly developing  commercial market in Ontario. Their primary benefit as a LID technology is in maximizing evapotranspiration for water balance targets.

 

Green roofs are sometimes referred to as 'ecoroofs', 'vegetated roofs', 'living roofs'.

{{TextBox|1=Green roofs are ideal for:

{{textbox|Green roofs are ideal for:

*Sites without significant space at ground level for infiltration,

*Sites without significant space at ground level for infiltration,

*Zero-lot line projects with outdoor amenity requirements,

*Zero-lot line projects with outdoor amenity requirements,

*Projects looking for accreditation with LEED v.4}}

*Projects looking for accreditation with LEED v.4}}

 

<p> Extensive green roofs are the most commonly used  type of green roof used for stormwater in our region. </p>

 

Extensive green roofs are the most commonly used  type of green roof used for stormwater in our region. </p>

<table class="table table-responsive table-striped">

<table class="table table-responsive table-striped">

<caption><strong>Types of green roofs: defined by construction depth</strong></caption>

<caption><strong>Types of green roofs: defined by construction depth</strong></caption>

</table>

</table>

<br>

<br>

<p>Intensive green roofs are commonly used for amenity space on condo developments or sometimes as urban farms. They are sometimes referred to as roof gardens and encompass diverse uses, design priorities and technical specifications.  In the most extreme examples, many urban parkettes  including large shade trees may be included in this class, if they have parking garages beneath. As such the discussion on this page is limited to extensive green roofs. </p>

Intensive green roofs are commonly used for amenity space on condo developments or sometimes as urban farms. They are sometimes referred to as roof gardens and encompass diverse uses, design priorities and technical specifications.  In the most extreme examples, many urban parkettes  including large shade trees may be included in this class, if they have parking garages beneath. As such the discussion on this page is limited to extensive green roofs.8

<p><strong>Additional components may include:</strong>

<li>an irrigation system</li>

<li>pre-formed tray modules</li>

 

'''Additional components may include:'''

*an irrigation system

*pre-formed tray modules

<div class="col-md-4">

==Planning Considerations==

Green roofs offer a variety of co-benefits beyond stormwater management. In urban centers they are often constructed to accommodate a roof terrace or amenity space. In this scenario the direct stormwater capture benefit is restricted to the areas with vegetation planted.  Another increasingly popular use for rooftop space is for urban farming. Again, the direct stormwater capture benefit is restricted to the areas with planters.

<gallery mode="packed" widths=300px heights=300px>

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.

GRmodules.png| Example schematics of extensive green roofs. On the left, a 'built up' system comprising layers: roofing membrane, drainage board, geotextile, planting medium and sedum mat; and on the right a pre-planted plastic module or tray.  

<h4>Amenity</h4>

<h4>Amenity</h4>

<p>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|rainwater harvesting]] for subsequent irrigation. Sedum and native species have all been shown to thrive with daily irrigation to saturation[http://grit.daniels.utoronto.ca/green_roof_image_index/#]. </p> 

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|rainwater harvesting]] for subsequent irrigation. Sedum and native species have all been shown to thrive with daily irrigation to saturation[http://grit.daniels.utoronto.ca/green_roof_image_index/#].

<p>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. </p>

 

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.

 

<h4>Biodiversity</h4>

<h4>Biodiversity</h4>

<p>Biodiversity opportunities are optimized by planting a variety of species. General advice on this has been prepared by the City of Toronto[https://www1.toronto.ca/City%20Of%20Toronto/City%20Planning/Zoning%20&%20Environment/Files/pdf/B/biodiversegreenroofs_2013.pdf]. 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. </p>

Biodiversity opportunities are optimized by planting a variety of species. General advice on this has been prepared by the City of Toronto[https://www1.toronto.ca/City%20Of%20Toronto/City%20Planning/Zoning%20&%20Environment/Files/pdf/B/biodiversegreenroofs_2013.pdf]. 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. </p>

 

<h4>Design for Maintenance</h4>

<h4>Design for Maintenance</h4>

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

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

<p>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>

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>

<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. </p>

<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.

<gallery>

 

<gallery mode="packed">

Roof Drain.jpg | Example of gravel edging around a roof, which needs weeding.

Roof Drain.jpg | Example of gravel edging around a roof, which needs weeding.

Red Drain.jpg| Example of gravel edging around a roof drain, which needs weeding.   

Red Drain.jpg| Example of gravel edging around a roof drain, which needs weeding.   

Native Child.jpg| The amenity value of this roof is enhanced by the tall and climbing plants screening the high safety fences.   

Native Child.jpg| The amenity value of this roof is enhanced by the tall and climbing plants screening the high safety fences.   

PondRd1.jpg

PondRd1.jpg

PondRd2.jpg| Very light maintenance has permitted a stand of Mullein to develop on this prairie style green roof, increasing the biodiversity value.   

PondRd2.jpg| Very light maintenance has permitted a stand of Mullein to develop on this prairie style green roof, increasing the biodiversity value.   

===Design===

==Design==

 

<h4>Roof</h4>

<h4>Roof</h4>

<p>Flat roofs should be graded without depressions, with positive drainage ≥2% (1:50) towards roof drains.  For roofs with pitch greater than 10% (1:10) additional check dams or cellular components should be included in the design. These structures reduce the flow rate of the draining water, and help to stabilize green roof components. Green roofs can be installed on slopes greater than 20% (1:5), but specialized design advice should be sought for the addition of components required to secure the green roof in place. </p>

Flat roofs should be graded without depressions, with positive drainage ≥2% (1:50) towards roof drains.  For roofs with pitch greater than 10% (1:10) additional check dams or cellular components should be included in the design. These structures reduce the flow rate of the draining water, and help to stabilize green roof components. Green roofs can be installed on slopes greater than 20% (1:5), but specialized design advice should be sought for the addition of components required to secure the green roof in place.

<p>Extensive green roofs do not require additional insulation layers. The underlying roof may be of  warm, cold or inverted design. </p>

Extensive green roofs do not require additional insulation layers. The underlying roof may be of  warm, cold or inverted design.

<p>Extensive green roofs add load of around 70 - 300 kg/m². A structural engineer should be consulted during design to account for the distributed loads including snow accumulation and live loads including maintenance staff.</p> 

Extensive green roofs add load of around 70 - 300 kg/m². A structural engineer should be consulted during design to account for the distributed loads including snow accumulation and live loads including maintenance staff.  

<p>Roof membranes should be waterproof, root resistant, resilient to temperature change, and comply with appropriate CGSB standards as specified in the Ontario Building Code. In most cases a new roof with a modern membrane will not require a separate root penetration barrier.  In retrofit scenarios an additional root barrier may be recommended to protect an older roof membrane. </p>

Roof membranes should be waterproof, root resistant, resilient to temperature change, and comply with appropriate CGSB standards as specified in the Ontario Building Code. In most cases a new roof with a modern membrane will not require a separate root penetration barrier.  In retrofit scenarios an additional root barrier may be recommended to protect an older roof membrane.

<h4>Drainage Layer</h4>

<h4>Drainage Layer</h4>

<p>The underlying drainage layer is most often a preformed plastic sheet, formed to include depressions for water storage and perforations to drain excess water. This design has the advantage of being most lightweight, but has minimal impact on flow rates once the water has percolated onto the roof membrane below. </p>

The underlying drainage layer is most often a preformed plastic sheet, formed to include depressions for water storage and perforations to drain excess water. This design has the advantage of being most lightweight, but has minimal impact on flow rates once the water has percolated onto the roof membrane below.

<p>An alternative drainage layer solution is to use a granular medium to increase the tortuosity of the flow path and slow peak flow rates. </p>

An alternative drainage layer solution is to use a granular medium to increase the tortuosity of the flow path and slow peak flow rates.

<h4>Filter Layer</h4>

<h4>Filter Layer</h4>

<p>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.</p>

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.</p>

<h4>Planting Medium</h4>

<h4>Planting Medium</h4>

{{:Green_roof_media}}

{{:Green_roof_media}}

<h4>Irrigation</h4>

<h4>Irrigation</h4>

<p>Regular irrigation has been shown to substantially reduce the stormwater capture benefit of an extensive green roof[http://ascelibrary.org/doi/abs/10.1061/(ASCE)HE.1943-5584.0001534].  One way to reduce the irrigation used on green roofs is through the use of electronic 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  prevent irrigation ahead of storm events[https://optirtc.com/products].   

Regular irrigation has been shown to substantially reduce the stormwater capture benefit of an extensive green roof[http://ascelibrary.org/doi/abs/10.1061/(ASCE)HE.1943-5584.0001534].  One way to reduce the irrigation used on green roofs is through the use of electronic 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  prevent irrigation ahead of storm events[https://optirtc.com/products].   

<p> Due to their limited water retention capacity, many green roofs are coupled with a cistern to capture the excess water. It then becomes desirable to use as much harvested water to regain the cistern capacity,  Green roofs can be irrigated to saturation daily throughout the growing season without damaging the vegetation. </p>

<p> Due to their limited water retention capacity, many green roofs are coupled with a cistern to capture the excess water. It then becomes desirable to use as much harvested water to regain the cistern capacity,  Green roofs can be irrigated to saturation daily throughout the growing season without damaging the vegetation.  

 

 

<table class="table table-responsive table-striped">

<table class="table table-responsive table-striped">

<tr class = "success"><td>Irrigation technology</td><td>Benefits</td><td>Disadvantages</td></tr>

<tr class = "success"><td>Irrigation technology</td><td>Benefits</td><td>Disadvantages</td></tr>

<tr><td>Drip or capillary</td><td>Harvested rainwater is readily used without further treatment <br>Uses less water</td><td>Planting medium does not 'wick' water sideways readily, so can lead to localized dry areas</td></tr>

<tr><td>Drip or capillary</td><td>Harvested rainwater is readily used without further treatment <br>Uses less water</td><td>Planting medium does not 'wick' water sideways readily, so can lead to localized dry areas</td></tr>

</table>

</table>

<p> 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.</p>

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.

 

<h4>Planting</h4>

<h4>Planting</h4>

<p>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. <em>Sedum</em> species are the most common choice, demonstrating excellent longevity in systems with or without irrigation. </p>

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. </p>

<p> 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 <em>Sedum </em> and native species can help with this. </p>

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.

See: [[Planting for Green Roofs]]

See: [[Planting for Green Roofs]]

<h4> Drains and Vegetation Free zones </h4>

<h4> Drains and Vegetation Free zones </h4>

<p>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</p>.  

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.

 

 

<gallery mode="packed" widths=300px heights=300px>

<gallery mode="packed" widths=300px heights=300px>

TD Bank.jpg|The vegetation on this extensive green roof is designed to withstand the deep shade of being in downtown Toronto.  

TD Bank.jpg|The vegetation on this extensive green roof is designed to withstand the deep shade of being in downtown Toronto.  

</div>

</div>

===Performance===

==Performance==

 

<h4>Water quantity</h4>

<h4>Water quantity</h4>

<p>Green roof performance has not been reported to reduce over time. Controlled studies have instead indicated that maturing green roofs may have improved water retention properties [http://www.sciencedirect.com/science/article/pii/S0022169417300768].</p>

Green roof performance has not been reported to reduce over time. Controlled studies have instead indicated that maturing green roofs may have improved water retention properties [http://www.sciencedirect.com/science/article/pii/S0022169417300768].

<h5>Water balance</h5>

<h5>Water balance</h5>

{{:Green roofs: Water balance}}

{{:Green roofs: Water balance}}

</panelWarning>

</panelWarning>

==Incentives and Credits==

 

===Incentives and Credits===

<h4>In Ontario</h4>

<h4>In Ontario</h4>

<strong>City of Toronto</strong> updated their 'Eco roof' incentive program in 2017 . It now includes grants for structural assessment and is available to non-profit organisations [http://www1.toronto.ca/wps/portal/contentonly?vgnextoid=e08354ae91cda510VgnVCM10000071d60f89RCRD].  

<strong>City of Toronto</strong> updated their 'Eco roof' incentive program in 2017 . It now includes grants for structural assessment and is available to non-profit organisations [http://www1.toronto.ca/wps/portal/contentonly?vgnextoid=e08354ae91cda510VgnVCM10000071d60f89RCRD].  

<h4>LEED BD + C v.4</h4>

<h4>LEED BD + C v.4</h4>

<p>LEED offer a relatively large number of points for green roofs compared to other LID technologies.</p>  

<p>LEED offer a relatively large number of points for green roofs compared to other LID technologies.</p>  

{{:LEED: Rainwater management}}

{{:LEED: Rainwater management}}

<h4>SITES v.2</h4>

<h4>SITES v.2</h4>

 

==External Links==

*[https://www.greenroofs.org/ Green Roofs for Healthy Cities]

 

===External Links===

<li>[https://www.greenroofs.org/ Green Roofs for Healthy Cities]</li>

<h4>Proprietary Systems</h4>

<h4>Proprietary Systems</h4>

{{:disclaimer}}

You may inform us of any omissions using the link below:

*[http://www.nlsm.ca/ Next Level Stormwater Management]

*[http://www.liveroof.com/ LiveRoof]</li>

<li>[http://www.nlsm.ca/ Next Level Stormwater Management]</li>

*[http://www.ginkgosustainability.com/ Ginkgo Sustainability]

<li>[http://www.liveroof.com/ LiveRoof]</li>

*[https://www.zinco.ca/ Zinco]</li>

<li>[http://www.ginkgosustainability.com/ Ginkgo Sustainability] </li>

*[http://www.vitaroofs.com/ VitaRoofs]

<li>[https://www.zinco.ca/ Zinco]</li>

<li>[http://www.vitaroofs.com/ VitaRoofs]</li>