Toronto Green Roof Bylaw and Eco-Roof Incentive Program — Mandatory Green Roofs on Large New Buildings, Funded by Cash-in-Lieu

Toronto's Green Roof Strategy was adopted in 2006, and the Green Roof Bylaw (By-law 583-2009) and the Eco-Roof Incentive Program followed in 2009. The bylaw applies to new developments above 2,000 m² gross floor area and requires 20–60% of available roof space to be green roof, scaled to building size. Developers may seek approval to pay $200/m² cash-in-lieu instead; those funds finance the Eco-Roof Incentive Program, which pays $100/m² for green roofs and $2–5/m² for cool roofs, plus structural assessment grants of up to $1,000 for existing buildings.
According to C40, about 420 green roof permits covering roughly 450,000 m² were issued between 2010 and 2017, and the incentive programme supported 336 projects. For incentive-funded projects only, C40 reports roughly 11 million litres of stormwater diverted from sewers a year (a saving of at least $100,000), about 1,000 MWh/year of energy savings and about 220 t of greenhouse gases avoided annually. A 1.5–2 °C local air-temperature reduction is an estimate that assumes widespread green roofs, not a measured result.
The Living Architecture Monitor gives a larger cumulative scale (about 1,200 projects, around 12.5 million sq ft) but states that its stormwater benefit is modelled from City data, not measured. Maintenance plans and membrane leak-detection tests are required at permit stage, and a recent City study is reported to find over 90% of green roofs flourishing.
Caution: the same publication reports that on 3 November 2025 the Ontario government revoked the section of the City of Toronto Act that enabled the bylaw, which puts the model's continuity at risk. This is a single-source report and should be verified before relying on it. Biodiversity and fire-risk effects are not quantified in the sources.

Read the full analysis: https://livingarchitecturemonitor.com/articles/legacy-of-toronto-green-roof-bylaw-wi25