Category: More
Take a Minute and Enjoy the Unfolding Spring Splendour of Sherway Gardens’ Green Roof
Next Level Stormwater Management was very honoured to kick off Sherway Gardens’ green roofs milestone 10th year by hosting participants of the Earth Tending Indigenous Green Infrastructure Training Program on May 23, 2024. The green roof tour was part of the week long training sessions led by Indigenous and non-Indigenous experts who “braid together Indigenous Knowledge with that of industry green infrastructure practices”. Earth Tending was created and is run by SpruceLab Inc. and sponsored by Miziwe Biik Aboriginal Employment and Training. Sherway’s 9500 square foot green roof was supplied by Next Level Stormwater Management and installed in 2014.
Earlier that day, Dr. Karen Liu provided an informative training session from her base in Vancouver, BC. Participants had great questions and comments. We look forward to more opportunities to learn and work together in the future.
Meegwetch to all participants, Gwen Lane and SpruceLab Inc. We feel very privileged to spend the day with you!
More Than 2.5 Million Square Feet Coast-to-Coast
NLSM is Canada’s leading supplier of pre-vegetated roofs such as the LiteN’Less™ and StormCap™ systems. We customize to local requirements. Offer warranty & maintenance support, provide stormwater calculations specific to location and building/roof type, stormwater test data & related innovative hydrologic modelling. Click here to get a quote or to design your next green roof.
High Performance. Low Emissions. Future-Proofed
The Toronto Green Standard version 4 (TGS v4) raises the bar for all new development in the city. Green roofs play an important role especially on tight, urban sites. TGS v4 applies to all new planning applications in the City of Toronto received on or after May 1, 2022. Below is a review of the requirements and how green roofs help meet them.
Five performance categories:
- Air Quality
- Building Energy, Emissions & Resilience
- Water Quality & Efficiency
- Ecology & Biodiversity
- Waste and the Circular Economy
Importance of Green Roofs
Green roofs, with their multiple benefits, play an important role in TGS v4 via 2 categories Water Quality & Efficiency (WQ) by Managing Stormwater and Ecology & Biodiversity (EC) through Landscape & Biodiversity.
WQ 1.1 Water Balance, Quality & Quantity Control
Tier 1 Water Balance requires the site to retain a minimum of 50% of the total average annual rainfall volume (or equivalent 5mm from each rainfall event) generated from all site surfaces through infiltration, evapotranspiration, water harvesting and/or reuse, in accordance with the Wet Weather Flow Management Guidelines (WWFMG).
Green roofs can retain rainfall through initial abstraction (IA). According to the WWFMG, the IA are 5mm and 7mm for extensive and intensive systems, respectively. Furthermore, stored water in the cistern can evapotranspirate on the green roof through irrigation water reuse. These mechanisms are key to achieve water balance on site. NLSM offers optional irrigation reports to support water balance calculations.
TGS v4 defines an Intensive green roof as having a minimum growing medium depth of 150 mm with a diverse mix of plants appropriate to the growing medium depth and roof height. On the other hand, extensive green roofs contain hardy, low-profile plants growing in less than 150 mm of growing medium.
WQ 1.3 On-site Green Infrastructure
Tier 1 requires the total landscaped site area, located at and above grade. It includes at least 1 of the following six green infrastructure features:
- A Green Roof covering at least 80% of Available Roof Space
- An Intensive Green Roof for 80% of the Green Roof Area provided
- A Biodiverse green roof to support pollinator species covering a minimum of 50% Green Roof Area
- 25% of the Lot Area at or above-grade, planted with native flower/pollinator species
- At-grade Bioretention facilities provided to capture and control 75% of runoff from on-site hardscape surfaces, or
- Reforestation of a portion of the site (beyond the limit of a stewardship plan)
Note that three of the six options above involve green roofs. Putting green infrastructure on the roof is particularly attractive for development in tight urban sites with perhaps zero lot lines where there is little or no space to accommodate green infrastructures at grade.
The TGS v4 defines a Biodiverse green roof as an Intensive green roof that supports pollinator species. It is located at or below the 8th storey of the building to maximize pollinator access and must follow the recommended plant species found in Appendix A of the Design Guidelines for Biodiverse Green Roofs, with at least two species in bloom at all periods over the growing season. The design must also address two or more applicable Design Strategies from section 4.2 of the guide as listed below:
- Increase depth of growing medium
- Vary composition (structure) of growing media
- Provide topographic variety
- Provide microclimates
- Diversity plant species
- Provide perching habitat
- Provide nesting opportunities
- Provide water source (s)
A permanent irrigation system is required on both intensive and biodiverse green roofs to provide supplemental watering as necessary. Direct access to the roof should be provided for maintenance through a door or hatch located away from the edges to enable safe maintenance. A maintenance contract is recommended for at least the first 5 years of the green roof to ensure it receives a good start.
EC 2.3 Green and Cool Roofs
Landscape & Biodiversity Tier 1 requires buildings, where the Green Roof By-law is applied, to install a green roof to meet the minimum requirements as stated in the bylaw, or where the bylaw does not apply, provides 100% of the Available Roof Space with one of a combination of the following:
- Green Roof
- Solar PV, or
- Cool roof
NSLM Green Roof Systems Comply with TGS v4
All NLSM green roof systems meet the TGS v4. NLSM offers optional professional engineer-stamped wind letter for submission to the City. This chart summarizes the compliance path and helps you select the system that best meets your project’s needs:
| Categories* | NLSM Systems | WQ 1.3 Compliance Options | WQ 1.1 Initial Abstraction** |
| Extensive | LiteN’LessTM II | 80% of available roof space | 5 mm |
| LiteN’LessTM III | 80% of available roof space | 5 mm | |
| StormCapTM | 80% of available roof space | 5 mm | |
| StormCapTM+Detention | 80% of available roof space | 5 mm | |
| TerraExt Sedum Standard | 80% of available roof space | 5 mm | |
| TerraExt with BioBerm | 80% of available roof space | 5 mm | |
| Intensive | Flora Garden | 80% of green roof area provided | 7 mm |
| Biodiverse | Alpine Meadow | 50% of green roof area provided | 7 mm |
| Alpine Meadow+ | 50% of green roof area provided | 7 mm |
** Based on Toronto Water’s Wet Weather Flow Management Guidelines (WWFMG)
Supplier of more than 2.5 M SQFT Coast-to-Coast
NLSM is Canada’s leading supplier of pre-vegetated roofs such as LiteN’Less™, Xeroflor® and StormCap™ systems. We customize to local requirements. Email or call (416) 637-5772 Ext 1.
Towards a Clean, Healthy and Sustainable Canada
McLoughlin Point Wastewater Treatment Plant, Victoria BC
Sitting majestically atop an escarpment in Esquimalt, the McLoughlin Point plant can treat 108 megalitres of wastewater per day to tertiary level – one of the highest levels possible. Its 1,700 m2 multi-level extensive green roof consists of a soilless system containing vegetation with low nutrient needs, which minimizes fertilizer use and potential leaching. BioBerm™s were incorporated as an innovative and cost-effective option to enhance biodiversity with a more expansive plant palette. The treatment plant and its roof work together to keep our water, and environment, clean and healthy.
Duet Condo, Victoria BC
Situated in Victoria’s historic James Bay, Duet offers urban living in harmony with nature and ocean in Canada’s west coast. The accessible rooftop patio is surrounded by a Xeroflor® XF301 Sedum Standard pre-vegetated green roof that offers year-round visual interest and requires minimal maintenance. It naturally cools the residence units in the summer and reduces the need for air conditioning.
Broadway Tech Centre, Vancouver BC
A 6.9-hectre business campus where its 8 low-rise office buildings have been awarded LEED and BOMA certifications in 2019. A key sustainable design feature is the 10,000 m2 lightweight, pre-grown soilless extensive vegetated roof system that was installed on the four main buildings. The green roofs absorb 10 million litres of rainfall every year, diverting it from the ocean and keeping Canada’s west coast clean and pristine.
Sherway Gardens Shopping Centre, Toronto ON
Toronto’s largest commercial green roof of 9,500 m2 offers neighbouring towers a pleasing view of numerous levels of vegetated rooftops that change with the seasons. The extensive green roof system was chosen to slow stormwater runoff from the roof. Because of its size and water retention capacity, the green roof reduced the size of the original storage tank required. The roof also contributed to the building attaining LEED certification.
Yonge Sheppard Centre, Toronto ON
Pollinator friendly flowers help honey bees thrive atop theYonge Sheppard Centre in the middle of one of Toronto’s busiest hubs. The TerraExt Sedum Standard green roof brings nature back amidst rows of retail shops and glass facades and towering skyscrapers. Urban beekeeping boosts pollination and improves sustainability, food security and biodiversity in cities. This venture is in collaboration with the Teddy Bee Honey Company. The green roof helped Yonge Sheppard Centre achieve BOMA Best Certification.
Two Old Mill, Toronto ON
This lush and varied green roof is a beautiful mix of extensive and intensive vegetated roof systems. The extensive lightweight and soilless system is comprised of loose-laid base layers and a pre-vegetated mat. Over 50% of the plant species selected for Two Old Mill are native to the area. Meeting the Toronto Green Development Standard Tier II helped the building achieve LEED Gold Certification. Award-winning and praised for its varied landscape and vibrant palette, this rooftop provides multiple environmental benefits.
Pavillon d’accueil au golf du parc Maisonneuve, Montreal QC
This green roof is innovative as it features a soilless extensive system with the BioBerm™ feature to create a meadow-like rooftop befitting the surrounding green oasis. The vegetated roof integrates the best features of extensive and intensive green roof systems to create topographic diversity and add texture and movement to an otherwise flat roofscape. It combines the soilless pre-vegetated system with mounding ornamental and native grasses and perennials that are planted through the sedum blanket in areas with built-up berms of growing medium.
Charles P. Allen High School, Bedford NS
The extensive green roof on this state-of-the-art building not only keeps the classrooms cool in the summer and extends the roof membrane’s service life, it also provides an innovative living learning space for the students. The Xeroflor® XF301 Sedum Standard vegetated roof system is very lightweight at only 57 kg/m2 when fully saturated yet able to resist high winds up to 133 km/h on Canada’s east coast.
Hampton Inn by Hilton, Halifax NS
Centrally located in downtown Halifax, Hampton Inn is an eco-friendly hotel that is just minutes from the historic Halifax Citadel. The 630 m2 Xeroflor® XF301 Sedum Standard vegetated roof system not only keeps the rooms cool in the summer and lowers the energy bill, it also supports an urban habitat for birds, bees and butterflies to promote biodiversity in Canada’s east coast.
The Biosphere, Montreal QC
We end our tour of Next Level’s green roofs across Canada with this landmark green roof. This time lapse video by Environment and Climate Change Canada shows the quick and simple installation of the extensive green roof system on the Biodome. The former World Fair pavilion is now fittingly a natural science museum dedicated to the environment.
This Canada Day, in support our collective reconciliation journey, NLSM donates to the Downie Wenjack Fund.
Supplier of more than 2.5 M SQFT Coast to Coast
NLSM is Canada’s leading supplier of pre-vegetated roofs such as LiteN’Less™, Xeroflor® and StormCap™ systems. We customize to local stormwater and biodiversity requirements. Email or call (416) 637-5772 Ext 1
Enhance Biodiversity
BioBerm™s are rounded mounds of growing media on an otherwise level vegetated roof. They offer a natural, seamless way to integrate extensive and intensive green roof systems. This not only adds visual interest but supports more varieties of plants and a wider range of wildlife. Biodiverse roofs can contribute up to 2 points under LEED v4.1 “Sustainable Sites – Protect or Restore Habitat”. See Portfolio of Green Roofs with Bioberms™.
Manage Structural and Cost Limitations
While intensive systems support greater biodiversity, they can be too heavy and/or expensive for many projects. BioBerm™ is a smart way to creatively manage structural and cost limitations. Designers can strategically add depth to those parts of roof that can support the added load, such as over a load-bearing beam or near a structural wall, while keeping weight and cost low with an extensive system on the rest of the roof.
Create Microclimates and Microhabitats
In addition, the transition between extensive and intensive systems creates localized hills and valleys on the roof. The hills favour drought tolerant plants while the valleys support taller and denser vegetation, which attract different insects, birds and wildlife. As a result, BioBerm™s can create different microclimates and microhabitats to support potentially higher biodiversity than an intensive system.
In Toronto, stormwater is often stored in underground cisterns to meet site runoff requirements. This water is reused through irrigation or toilet flushing to create storage space for the next rain event. BioBerm™s enable designers to combine plants with high and low irrigation needs on one roof, so the green roof will evapotranspirate more when water is available but perverse moisture when the tank is empty.
Steps How to Create a BioBerm™?
Although not necessary, a good way to create a BioBerm™ is to cover the entire growing substrate surface with a pre-vegetated sedum mat. Simply cut slits and plant plugs through the openings into the growing medium underneath. The pre-vegetated mat has many benefits to offer.
Sedum Mat is an Instant Green “Cover Crop”
While the native plant plugs grow, the sedum mat prevents wind and water erosion of the growing medium during establishment. It also acts as a “living mulch” to preserve soil moisture, reduce irrigation needs and minimize airborne weed encroachment.
Many native and adapted vegetation will thrive in 100-200 mm of growing medium in the BioBerm™. Select plants whose natural habitats are similar to the rooftops and avoid invasive species. Design plant palettes that offer longer bloom time to provide nectars for bees and butterflies and produce seeds and berries for birds. City of Toronto’s Design Guidelines for Biodiverse Green Roofs is an excellent resource in creating a successful biodiverse green roof.
Supplier of more than 2.5 M SQFT Coast-to-Coast
Canada’s leading supplier of pre-vegetated roofs, NLSM customizes to local requirements, offers warranty & maintenance support, provides stormwater calculations specific to location and building/roof type, stormwater test data & related innovative hydrologic modeling. Click here to get started on your next green roof.
Built-in-Place and Modular Vegetated Systems
Traditionally, vegetation has been established on roofs using plugs, cuttings or seeds. These are called built-in-place vegetated systems. The initial vegetation coverage typically ranges 5-15% and it takes regular TLC (water, weed and feed) and patience (1-3 years) for the young plants to mature and establish.
Increasingly, vegetation is first pre-grown in modules on the ground for quicker establishment on the roof. These are called modular vegetated systems. These pre-vegetated modules contain mature plants with 80+% vegetation coverage at delivery, and typically takes only one growing season to establish on the roof.
If we could use an analogy comparing establishing a green roof to starting a front lawn, built-in-place systems would be akin to sowing seeds. Modular systems would be equivalent to laying sod. Instant green, ease of installation, reduced establishment time and maintenance efforts are some attributes that make modular vegetated systems such as mats and trays popular in North America.
Modular Pre-Vegetated Mat and Tray Systems
Pre-vegetated mats contain vegetation planted in a shallow growing medium (2-3 cm) on a vegetation carrier. Natural carriers made of coir fibre matting decompose over time and integrate into the media. Synthetic carriers consisting of 3D entangled mesh provide enhanced root anchorage and mat integrity, which are suited for sloped roofs. They are durable and can be readily rolled back, even many years later, for membrane access. Pre-vegetated mat systems are loose laid, yet highly wind resistant.
Pre-vegetated trays contain vegetation planted in containers resembling shallow planter boxes. They are made of plastics or metals and come in different sizes, typically containing 5–20 cm of growing medium. Some trays are designed to be fastened or interlocked together for stability and wind resistance. There are also trays that are made of natural materials that decompose and integrate into the media over time.
Why Vegetated Mat Systems Dominate
Green Roofs for Healthy Cities, a North American green roof industry association, conducted a detailed market survey in 2016. They showed that mats topped the North American market at 47% followed by trays at 39%. The difference is even higher when it comes to extensive systems 56% for mats vs. 29% for trays.
- Lighter weight: 60-150 kg/m2 for mat systems vs. 200-300 kg/m2 for trays
- More economical: $150-200/m2 for mat systems vs. $250-350/m2 for trays
- No membrane puncture hazards: mat systems are flexible and do not contain any sharp edges or corners
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Pre-vegetated mats are easy to cut and conform around drains, penetrations and curved and organic landscapes. Easy to cut and conform: mat systems are easier and less messy to cut around drains and penetrations, they fit curved and organic landscape design without looking “pixelated” and conform well to 3D contours such as dome or wavy shaped rooftops
- Quicker installation: a typical mat is about 10X the size of a typical tray. Mats and baselayers are flexible and much easier to cut than the hard trays. These save as much as 25% labour on large roofs
- Easy membrane access: mat systems, especially soilless, can be readily rolled back or cut for membrane access. It is more difficult with trays as they are either interlocked or “jammed” tight over time.
Biodiversity in Trays and Mats
Trays, especially deeper ones (10–20 cm), can accommodate larger plants. Extensive mat systems can also incorporate larger plants with the BioBerm™.
Supplier of more than 2.5 M SQFT Coast-to-Coast
Canada’s leading supplier of pre-vegetated roofs, NLSM customizes to local requirements, offers warranty & maintenance support, provides stormwater calculations specific to location and building/roof type, stormwater test data & related innovative hydrologic modeling. Click here to get started on your next green roof.
More than 85 Years Experience
Next Level Stormwater Management (NLSM) is Canada’s leading supplier of pre-vegetated roofs such as LiteN’Less™ and StormCap™ systems. NLSM’s team has more than 85 years of combined green roof industry experience: helping with stormwater calculations and technical advice, design, planning and maintenance support, assisting with required documentation, issuing P.Eng-stamped wind reports and supplying and delivering the complete system package.
Enjoy this rare bird’s eye view of NLSM green roofs!
Supplier of more than 2.5 M SQFT Coast-to-Coast
Canada’s leading supplier of pre-vegetated roofs, NLSM customizes to local requirements, offers warranty & maintenance support, provides stormwater calculations specific to location and building/roof type, stormwater test data & related innovative hydrologic modeling. Click here to get started on your next green roof.