Category: Case Studies
The Business Case for Green Roof Amenity Space
The following blog post summarizes key insights from “Sky‑High Returns: The Economic and Social Case for Green Roof Amenity Space,” featured in the Spring 2026 issue of Living Architecture Monitor.
By Dr. Karen Liu, Green Roof Specialist, Next Level Stormwater Management
As North American cities densify to address climate change, population growth, and housing affordability, green space at ground level is becoming increasingly scarce. In this context, green roof amenity spaces are no longer optional. Instead, they are essential urban infrastructure that supports human well‑being while delivering measurable economic value.
Research increasingly demonstrates that the benefits of green roofs extend well beyond environmental performance. In the United States, apartment buildings with green roofs in New York City’s Battery Park City neighbourhood achieved average rents 16% higher than comparable buildings without green roofs. In Oak Park, Illinois, second‑floor condominium units with private green roof terraces sold for 12.4% more per unit, while green roof construction costs were significantly lower than the added value.
Canadian research shows similar results. A CMHC study estimated that recreational rooftop gardens can increase property values by approximately 11%. More recently, a University of Northern British Columbia study analyzing over 2,000 property listings found that green roofs increased average property values by approximately $700,000 in Vancouver, and added approximately $325 per square metre ($30 per square foot) in Toronto. Given that typical extensive green roof costs in Toronto range from $25–35 per square foot, many projects can recover all or most of their investment through increased listing prices alone, before accounting for energy savings, stormwater compliance, and extended roof membrane lifespan.
Multi-functional Rooftop Hardscapes
Municipal requirements for outdoor amenity space and stormwater management often compete for limited rooftop area on new developments. This challenge can be exacerbated by restrictions on “double dipping.” For example, the City of Toronto limits green roofs to no more than 25% of required outdoor amenity space for apartment buildings. Fortunately, emerging design strategies allow amenity spaces to also manage stormwater effectively.
Our SpongeBase™ system adds retention and detention capacity and effectively transforms otherwise impervious amenity surfaces into pervious ones to help meet the site’s stormwater management targets. SpongeBase Retention inserts water-absorbent materials in the void space under patio pavers or decking to retain water and help meet municipal water balance target. SpongeBase Detention involves detention elements that convert the space below the rooftop patio into temporary detention reservoirs to meet quantity control requirement. These tools can be seamlessly integrated with green roofs or blue‑green roof systems to create dual‑function green roof amenity spaces that serve people and infrastructure needs simultaneously.
Growing Demand for Green Roof Amenity Space
Beyond financial and regulatory benefits, green roof amenity spaces deliver significant social and health value. They provide restorative outdoor environments for residents, workers, students, patients, and visitors, supporting mental health, reducing stress, and fostering social connection. Research consistently shows that even visible green roofs, including those on schools and hospitals, contribute to improved well‑being and learning outcomes.
While returns vary by building and location, the evidence is clear: green roof amenity spaces increase property value, support urban resilience, and improve quality of life. With more than 80% of people in Canada and the United States living in cities, designing multifunctional rooftop green spaces is becoming essential to meeting the needs of urban communities.
Technical Expertise and Project Support
Next Level Stormwater Management works with design teams to supply and integrate green roofs and amenity spaces that can increase ROI, extend roof membrane service life and improving the building’s return on investment.
Beyond supplying systems and products, Dr. Karen Liu and the rest of the Next Level Stormwater Management team provide technical guidance, system selection and design coordination services to help project teams confidently deliver green roof amenity spaces that satisfy performance targets and user expectations. This collaborative approach supports better outcomes and long‑term performance.
About the Author
Dr. Karen Liu is a leading expert in green roof research with more than 25 years of experience spanning research, standards development, and hands-on project delivery. She has led pioneering green roof research programs in Canada, helped develop national wind testing standards for vegetated roofing, and contributed to dozens of influential technical and academic publications. Karen has worked on hundreds of green roof projects across North America, Europe, and Asia, and is actively involved in advancing industry training and professional standards. She currently serves on multiple boards and committees supporting green infrastructure and landscape architecture.
Canada’s Supplier of more than 2.5 Million SQFT
Next Level Stormwater Management (NLSM) is Canada’s leading supplier of high performance rooftop retention and detention solutions such as LiteN’Less™, StormCap™, Alpine Meadow and SpongeBase™. Ready to start your green roof project? The NLSM team has more than 90 years combined industry experience and here to support you at every stage from design and construction to maintenance. Please email us or call 416-637-5772 today.
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 to Soilless and Extensive Green Roofs
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.
9500 m² retains 340,000 litres ≈ 2,500 bathtubs of rainwater
Download the Case Study PDF CF Sherway Gardens North Expansion
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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. Watch 2025 video short of Sherway and 2020 green roof video that includes CF Sherway Gardens and see how well it continues to perform.
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.
Green Roof that Retains and Detains
Download the PDF Case Study Monza
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Delivers the Ideal Solution
The StormCap™ Detain 3° green roof delivered the perfect solution for Monza Condo Residences by Benvenuto Group to meet detention storage requirements on a challenging site in Toronto. Studio TLA and LEA Consulting upgraded the orinally planned vegetated roof to the highly specialized StormCap™ Detain 3° green roof when permeable pavement and subsurface detention was not feasible and could not meet stormwater management requirements. This green roof is an ideal solution for urban infill development, and areas with a high water table. Detention reduces and dealys peak flow, helps mitigate flash floods and continues to be reliable in back-to-back, second day storms. Unlike blue roofs, StormCap™ Detain 3° friction detention works efficiently on low-sloped roofs. Customizable detention layers can store up to 100 mm (4″) of additional water on your roof. This helps downsize or eliminate the need for underground storage tanks, freeing up valuable space and delivering a strong return on investment.
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.
Underutilized Roof Manages Stormwater
Download the PDF Case Study Precise ParkLink
Delivers the Ideal Solution
This lightweight and soilless green roof provided the ideal solution for Precise ParkLink’s new office building to meet Toronto’s Zoning By-law 569-2013 that requires commercial and industrial buildings to include soft landscaping to support stormwater management, biodiversity, and urban cooling.
Precise ParkLink received a variance to save valuable parking space at lot level by installing a green roof on an otherwise underutilized rooftop.
Green roofs are a useful tool in the stormwater management toolbox, especially when building in dense urban centres. They achieve water balance and quantity control to deliver strong return on investment. One such quantity control green roof is the StormCap™ Detain 3° that can help downsize or eliminate underground storage tanks and free up valuable space.
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.
Amenity Space with Stormwater Management & Energy Savings
Download the PDF Case Study of Robert C. Austin Town of Halton Hills Public Works Operations Centre, Halton Hills
Learn more about the designer and vegetated system at Project Details
Supplier of More Than 2.5 M SQFT Coast to Coast
Award-winning BTC manages up to 340,000 litres of rain
Download the PDF Case Study Broadway Tech Centre, Vancouver, BC
Learn more about designer and vegetated system here Project Details
Stormwater Management, Aesthetics & More
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Certificate of Completion will be issued for CE Credits
Supplier of more than 2.5 M SQFT Coast to Coast
Award of Excellence Recipient
Download the PDF Two Old Mill Case Study
Learn more about designer and vegetated system here Project Details
Biodiverse Amenity Space
Green roofs provide an enjoyable green space for building residents as well as an urban habitat for insects and pollinators. A biodiverse green roof offers greater conservation and environmental benefits, such as stormwater management, compared to conventional roofs.
The extensive lightweight and “soilless” system used on Two Old Mill is 30 mm thick and is comprised of loose-laid base layers and a pre-vegetated mat. The mat includes 8-10 species of sedum and arrives mature with 80 per cent foliar coverage. This extensive system is beautifully blended with a vibrant palette of perennials planted in an intensive green roof system.
Enjoy More Beautiful Photos of Two Old Mill
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. Click here for a green roof to meet your design goals.
Download the PDF Case Study Coquitlam Water Treatment Facility, Coquitlam, BC
Learn more about designer and vegetated system here Project Details
Stormwater Management, Aesthetics & More
The Coquitlam Watershed and its water treatment facilities provide approximately 370 million litres of potable water per day on average to Metro Vancouver residents. Protecting the region’s water quality and managing stormwater runoff were key concerns in building the Coquitlam UV Disinfection Facility. Designed to achieve LEED Silver classification, a low maintenance, “soilless” vegetated roof system was installed in 2014. This soilless green roof has a very high-water retention to weight ratio. At a total profile of 63 mm, the system weighs 57 kg/m2 at saturation with a maximum water storage of 34 l/m2.
Pre-grown locally, the sedum blankets are harvested like sod and simply installed by rolling directly on top of loose base layers that consist of retention fleece, drainage and root barrier. This green roof system was vetted and approved by local authorities for minimal nutrient leaching and preserving the pristine watershed. Controlled release fertilizer is applied once a year minimizing nutrient runoff. With no loose growing medium, this system also reduces soil erosion on the sloped roof.
Join us for Free, Live Webinars
Certificate of Completion will be issued for CE Credits
NLSM has supplied more than 2.5 M SQFT coast to coast