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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.
Treatment Plant features a 1700 m² soilless green roof.
Learn more about Project designer and vegetated system
The McLoughlin Point Wastewater Treatment Plant was built to LEED Gold certification requirements to do a big job with a relatively small footprint. The sustainable design elements include a 1700 square metre soilless green roof to restore the site’s natural landscape and provides habitat for wildlife. The pre-vegetated system consists of a sedum mix and no loose growing medium, making it very lightweight. Sedum are heat and drought tolerant, a necessity to survive the dry summers on the Island. The plants require no mowing, pruning or trimming, and very little water and nutrients to survive. These succulents store water in their leaves, stems and roots, which allows them to thrive on the rooftop.
BioBerm™ Brings Biodiversity
The treatment plant also includes BioBerm™s – rounded mounds of growing medium seamlessly integrated into the minimalist “soilless” green roof. BioBerm™s combine extensive and intensive systems to add visual interest, support a greater variety of plants and allow for greater choice of habitat for a wide range of wildlife. Furthermore, biodiverse roofs can contribute up to 2 points under LEED v4.1 “Sustainable Sites – Protect or Restore Habitat”.
NLSM has supplied 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.
Read Rooftop Stormwater Management Technologies for Climate Change Adaptation and Resilience by Dr. Karen Liu and Sasha Aguilera in Construction Canada January 2022 Vol. 64 No. 1.
The article looks at the increased intensity and frequency of recent extreme weather events such as heatwaves, rainstorms and hurricanes and how green infrastructure helps urban centres become more resilient. It includes info about new flood maps, efforts on climate action and how green infrastructure, including green roofs, blue roofs and blue-green roofs are being used to manage stormwater and mitigate flooding of urban centres.
Supplier of Green Roof Solutions Nationwide
With over 2.5 million square feet installed, NLSM is Canada’s leading supplier of pre-vegetated systems and accessories to suit any design. Our systems are independently tested to CSA A123.24 standards. We provide P.Eng stamped letters as well as expert support in design, budgeting, documentation, warranties, and maintenance. Email or call (416) 637-5772 Ext 1.
A Tale of Two Assemblies…CRA versus PMRA
Conventional (CRA) and protected membrane roof assemblies (PMRA) are the most common low-slope commercial roofing systems in Canada. The key difference is the placement of the roof membrane relative to the thermal insulation.
While installing a vegetated or green roof system on a conventional roof is relatively straightforward, component configuration can be trickier with PMRA.
Here, we untangle the two so you can design and construct a vegetated system on either roof assembly with confidence.
What is a Green Roof’s Conventional Roof Assembly?
In a Conventional Roof Assembly, the roof membrane is installed on top of the thermal insulation. Although many insulation products are suitable, choose ones with sufficient compressive strength to support the weight of the vegetated system. A cover board is recommended to spread the load across the insulation.
The vegetated system is installed above the roof membrane, starting with the root barrier and followed by the rest of the buildup. Some roofing manufacturers recommend laying a protection fleece or a protection board to protect the roof membrane from foot traffic during the vegetated system installation.
What is a Protected Membrane Roof Assembly (PMRA)?
In a Protected Membrane Roof Assembly or PMRA, the thermal insulation is placed on top of the roof membrane. It is also called Protected Membrane Roof (PMR), Inverted Roof Membrane Assembly (IRMA), or upside-down roof, referring to reversed positions of the membrane and insulation compared to the conventional assembly.
The insulation is now exposed to the elements and must resist water absorption, thermal expansion and contraction, freeze-thaw cycling…etc. The only insulation that is suitable for PMRA is extruded polystyrene (XPS), which is ballasted by aggregates, pavers or concrete topping to prevent flotation and wind uplift.
The amount of ballast required depends on the thickness of the XPS used, starting from 60 kg/m2 (12 psf) for 50 mm (2”) of XPS, and increases by 24 kg/m2 (5 psf) for every additional 25 mm (1”) of XPS. A filter fabric is usually placed between the XPS and the ballast, which not only prevents dirt from settling in the joints but allows the XPS to “raft” or float together, thus reducing the amount of ballast required.
Can a Vegetated System Act as Ballast in a Green Roof?
A vegetated system can replace some or all of the ballast required depending on its dry weight. This is the lowest weight when there is no moisture present in the system. This can be measured using ASTM E2397. Let’s look at an example where 60 kg/m2 (12 psf) of ballast is needed to hold down the XPS on a PMRA.
Let’s say “Vegetated System A” weighs 70 kg/m2 (14 psf) when dry and 100 kg/m2 (20 psf) fully saturated. It can replace all the ballast required as its dry weight is greater than 60 kg/m2 (12 psf). Now, we have a lighter “Vegetated System B” that weighs 40 kg/m2 (8 psf) when dry and 70 kg/m2 (14 psf) fully saturated. We will need at least 20 kg/m2 (4 psf) of ballast to make up the 60 kg/m2 (12 psf) required.
The ballast aggregates are installed on top of the insulation/filter fabric and double the duty as a drainage layer for the vegetated system. Note that if the vegetated system is used to ballast the XPS either partly or entirely, it cannot be removed without substituting alternative ballast in the future.
Where Does the Drainage Go in a Green Roof?
DuPont, a major XPS manufacturer, recommends that the drainage should always be above the XPS. This allows the water to drain off the top surface of the insulation and creates a “diffusion open” assembly. The drainage provides a ventilating air space for topside venting to create open diffusion.
Although installing a drainage layer under the XPS can divert water to drains quicker, unfortunately, it can create a “convective loop” below the XPS. Air can move through the drainage layer and potentially reduce the overall insulation value.
As a result, DuPont recommends installing the drainage above the XPS to ensure the insulation value is maximized. A good positive slope to drain is an effective and better way to divert water to drains in PMRA.
Root Barrier Installation for a Green Roof
DuPont recommends the root barrier be installed above the roof membrane and under the XPS. Root barriers are flexible sheets made of polyethylene or polypropylene that physically block root ingress to the roof membrane.
These plastic sheets are vapour impermeable. If placed on top of the XPS, water vapour in the system cannot escape and can potentially be driven back into the XPS, which can reduce its insulation value. Thus, a root barrier should be placed below the XPS to achieve “open diffusion”.
Green Roof Best Practices for Specifications
As the root barrier often falls under “Vegetated System” instead of “Roofing System” in construction specifications, this can create a workflow/coordination issue. Therefore, we recommend the root barrier be specified under “Roofing System” so it can be installed by the roofing contractor. It should also be referenced under the “Vegetated System” so the green roof contractor is aware it exists but focuses on the rest of the vegetated system buildup above the PMRA.
Further Reading and Reference Material
DuPont’s “Vegetative Roof PMR – A Design Primer” is a good reference that offers practical building science advice for designers who are interested in vegetating PMRA. All NLSM’s systems can be installed on conventional and PMRA.
Supplier of more than 2.5 M SQFT Coast-to-Coast
NLSM is Canada’s leading supplier of pre-vegetated roofs that are customized to local requirements. NLSM offers warranty & maintenance support, provides stormwater calculations specific to location and building/roof type, stormwater test data & related innovative hydrologic modelling. Contact NLSM for the best green roof option to meet your design goals.
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.
9500 m² retains 340,000 litres ≈ 2,500 bathtubs
Download the PDF Case Study CF Sherway Gardens North Expansion
Learn more about Project designer and vegetated system
Canada’s Largest Soilless Green Roof
The 9500 m² soilless vegetated green roof was designed to meet CF Sherway Gardens’ Stormwater Management Program goals for their north expansion. Installed in 2014, the green roof is one of the sustainability features that helped Sherway earn the BOMA Best Gold and LEED Certification. See video of green roofs including CF Sherway Gardens, here
Enjoy More Beautiful Photos of Sherway Gardens
More Than 2.5 Million Square Feet 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.
Stormwater Management, Energy Savings and Enjoyable Amenity Space Download PDF Case Study Robert C. Austin Town of Halton Hills Public Works Operations Centre
Learn more about designer and vegetated system here Project Details
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