In 2009, the Canadian city of Toronto, Ontario, passed the first law in North America requiring green roofs on newly constructed buildings over a certain size. Now, more than 15 years after Toronto’s Green Roof Bylaw was passed, the city has installed 640 new green roofs under the law.

And the rest of North America is catching on. The number of green roofs on the continent is estimated to have grown significantly, with cities across the continent implementing increasingly stringent requirements.

It’s common to call anything that’s more sustainable than standard practices “green.” But a green roof, also called a living roof, is not just any sustainable roofing material; it is a roofing system that supports living plants. Green roofs have been around in the form of sod roofs since at least the Middle Ages.

A modern green roof involves more than just plants. It needs high-quality waterproofing and protection against root damage, a drainage system, filter cloth, and a lightweight growing medium. The plants may be small, drought-tolerant ones like sedums, or larger grasses. The system can be modular or site-built, and depending on the planting medium depth, may even resemble a natural meadow or a garden with shrubs and trees.

Project Drawdown ranks green roofs and cool roofs as #73 in their list of solutions to global warming, with an anticipated 0.77 gigaton reduction in carbon dioxide by 2050. If green roofs cover 30% of roof space by 2050 and cool roofs cover 60%, approximately 407 billion square feet of efficient roofing would be in place globally.

Despite growing support, several challenges continue to limit widespread implementation.

• High Costs: Initial installation costs remain a financial barrier. A University of Michigan study found that a 21,000-square-foot green roof costs about $100,000 more to install than a conventional roof. Maintenance costs and the need for specialized expertise add to these expenses.
• Structural Concerns: Existing buildings, especially older ones, may not have been designed to bear the additional weight of saturated soil and vegetation. Assessing and potentially reinforcing structural capacity adds complexity and cost.
• Technical Challenges: The design and construction process requires coordination across multiple disciplines. Green roof components appear on architectural, structural, landscape, and plumbing drawings, while civil engineers handle exterior drainage—creating potential for coordination challenges.
• Policy and Regulatory Gaps: In municipalities without green roof policies, the permitting process for a living roof can pose barriers. Complex approval timelines often mean stormwater management plans are submitted before green roof designs are finalized.

Lack of awareness of green roofs across the public and private sectors, insufficient promotion by government entities, and limited experience with green roof systems in some regions continue to slow adoption. More research is needed to confidently price the public and environmental benefits of green roofs, including their distributed energy savings and cooling effects on surrounding buildings.

A 2024 study published in Nature Cities reports that Seoul’s city-wide green roof implementation could reduce building energy use intensity by up to 7.7%. Another comprehensive 2024 study in Nature Urban Sustainability projected that by 2100, green and cool roofs could reduce HVAC use by up to 71.72% in six cities studied. A 2023 meta-analysis found that green roofs reduce rooftop surface temperatures by an average of 30°C during summer months.

A U.S. General Services Administration study that was removed from its website following the Trump Administration’s anti-green guidance estimated that the heating and cooling savings from green roofs on commercial and public buildings paid back the cost of installation in about 6.2 years.

Residential and Commercial Applications

Green roofs on private residences are very efficient. Despite the high cost of design and installation, which has slowed their adoption as a standard roofing option, they can provide lifetime savings.

Single-family homes accounted for less than 2 percent of green roofs in the U.S. in 2015. Multifamily homes, on the other hand, provide economies of scale that can justify the expense (and sometimes have the square footage to trigger green roof requirements), accounting for 22 percent of green roof projects. That still leaves the vast majority of green roofs to industrial and commercial buildings.

But private homeowners need not despair. Many of the incentives for green roof construction are also available for single-family residences.

Several impressive green roof installations have been completed in recent years:

Will’s Garden at Carle Foundation Hospital is a 2023 Award of Excellence winner that features a therapeutic garden in Urbana, Illinois. The immersive, wheelchair-accessible rooftop included significant technical achievements that allow the plants to grow in only six inches of media.

Construction began on the LXK Office and Residential Campus in Berlin. A designed development, it includes green rooftops and terraces.

Kö-Bogen II, in Düsseldorf, Germany, is a commercial complex features one of Europe’s largest green façades with over 30,000 hornbeam plants that provide a “green heart” and “urban mountain” in the city.

The Vancouver Convention Centre’s six-acre living roof remains the largest in Canada.

The California Academy of Sciences in San Francisco features 1.7 million plants in its living roof.

Chicago City Hall’s green roof remains one of the most studied examples, with more than 20,000 plants from 150 species.

Carrots and Sticks: Policy Approaches

Toronto became the first city to require green roofs in 2009; in 2019, New York City became one of the latest major cities to pass mandatory legislation. At least 25 cities in North America now have programs to encourage green roofs, with a trend toward making them mandatory rather than voluntary. The organization also developed the Living Architecture Performance Tool, a free rating system and best practice guide for policymakers.

These cities are taking the next step toward making green roofs a fixture in their skylines:

Portland, Oregon (2020): The city’s “ecoroof” requirement went into effect, mandating that vegetation must cover 100% of roofs on buildings in the central city over 20,000 square feet (with some exceptions).

Denver, Colorado: Denver’s green roof ordinance requires new construction and existing buildings over 25,000 square feet to dedicate portions of their rooftops to vegetation or solar panels. The percentage of vegetation required increases with building size: 20% for 25,000 sq ft buildings, up to 60% for buildings 200,000 sq ft or larger.

San Francisco: The city implemented the first green roof mandate in the United States in January 2017 with its “Better Roofs Ordinance,” requiring living roofs on most new construction as part of the Sustainable City initiative.

New York City: Through the Climate Mobilization Act, Local Laws 92 and 94, passed in 2019, require solar panels or green roofs on all new construction and buildings undertaking major roof renovations. Additionally, the city’s Resolution 66 tripled the tax break for property owners who install green roofs in high-priority areas.

Cities have also added financial incentive programs to the inherent benefits of green roofs. Check your community’s official website to discover whether financial assistance is available for green roof installation.

For example, New York City’s Green Roof Property Tax Abatement Program offers building owners $4.50 per square foot of green roof, or a maximum abatement of $100,000 per facility. The city’s Department of Environmental Protection Green Infrastructure Grant Program reimburses private building owners up to 100% of the cost of installing a green roof.

Chicago’s Sustainable Development Policy provides a Floor Area Ratio (FAR) bonus for developers who include green roofs, allowing them to construct more units on the same lot.

Many municipalities are adding new stormwater fees in response to climate change. These regulations often include tax credits for green roof installation, which are calculated based on the area covered or the effectiveness in reducing runoff.

Green Roofs for Healthy Cities updated its policy guide in 2023 to provide essential information for professionals, policymakers, and advocates. The guide covers regulations, incentives, and approaches across North America.

The movement toward green roof policies continues to gain momentum. Organizations like Green Roofs for Healthy Cities offer training and accreditation programs, including the Green Roof Professional (GRP) and the Green Roof Installation and Maintenance Professional Certification (GRIMP), helping build expertise in the field.

New green roof policies are appearing all the time. The benefits—from reducing air conditioning needs by up to 75% to managing stormwater, improving air quality, and providing urban wildlife habitat—make them an increasingly attractive option for sustainable development. For the most current information on policies and programs in your area, consult:

Editor’s Note: This article was updated in November 2025 to include recent research, policy developments, and examples of green roof installations across North America.