Policy Brief: Sustainability and Social Entrepreneurship Fellowship 2025

February 18, 2026

Bloom Above Green Roof Retrofits Policy Brief

Who is this aimed at

Municipal engineers and infrastructure planners
Halton Region policymakers and sustainability oﬃcers
Facility managers of public and private buildings
Urban development consultants
Environmental advocacy groups

Key messages

Green roofs reduce urban heat island eﬀects and mitigate climate change.
Retro-fitting roofs improves stormwater management and ﬂood resilience.
Municipal buildings, such as long-term care homes, are ideal pilot sites.
Green roof retroﬁts contribute to Halton Region’s Net Zero by 2045 target.

Policy options

Pilot Retroﬁt Program: Retroﬁt one municipal building (Allendale Long-Term Care Home) to assess feasibility and cost-eﬀectiveness.
Incentive-Based Retroﬁt Strategy: Oﬀer rebates or tax credits for commercial and residential green roof installations.
Mandatory Green Roof By-law: Implement mandatory green roof coverage for new developments and major renovations.

Executive Summary

Halton Region is increasingly vulnerable to climate-related challenges, including ﬂooding caused by intense storms and rising urban temperatures due to the urban heat island effect. Existing infrastructure is not equipped to manage these environmental pressures. Green roof retroﬁts over a sustainable and cost-effective solution that addresses both stormwater management and excess urban heat.

This policy brief proposes piloting a green roof retroﬁt on a regional facility, such as the Allendale Long-Term Care Home, to assess performance, cost, and scalability. Research from cities like Toronto and studies by the National Research Council of Canada show that green roofs can reduce stormwater runoff by up to 65%, lower rooftop temperatures by 2–3°C and extend roof lifespan signiﬁcantly.

We recommend launching a municipal pilot project, integrating green roof retroﬁts into Halton’s sustainability policies, and exploring funding support through national green infrastructure programs. This project will serve as a replicable model for broader implementation across municipal, commercial, and residential sectors, supporting Halton’s Net Zero by 2045 target.

Lark Scientific’s Role

Lark Scientific supported this research as part of its collaboration with the University of Waterloo’s EWEAL program, providing technical expertise and resources to help bridge academic insights with practical municipal applications. By contributing to evidence-based environmental solutions like green roof retrofits, Lark Scientific is helping accelerate climate adaptation strategies in communities across Canada.

Problem Statement

Halton Region is facing increased risks from climate change, particularly from more frequent and intense storms and rising urban temperatures. The existing infrastructure is not adequately equipped to handle stormwater runoﬀ, leading to increased ﬂooding and infrastructure strain.

Additionally, widespread concrete surfaces exacerbate the urban heat island eﬀect, making city centers several degrees hotter than surrounding rural areas.

Without proactive retroﬁtting, these issues will place mounting stress on public services and residents’ well-being. Engineering solutions like green roofs offer dual-function benefits by both reducing heat and capturing stormwater runoff.

Background

Halton Region’s sustainability strategy includes emissions reductions, natural heritage protection, and integrated growth management. However, there are currently limited plans or regulatory frameworks in place to support green roof infrastructure. While policies address stormwater management and tree canopy expansion, building-scale green infrastructure remains underutilized.

Inspiration can be drawn from cities like Toronto, which adopted a Green Roof Bylaw in 2010, leading to over 500,000 square meters of vegetative rooﬁng and proven environmental and economic beneﬁts.

Research Overview

Numerous studies support the ecological, economic, and social beneﬁts of green roofs:

Toronto Green Roof Bylaw: Reduced building energy use by 25% in summer, extended roof life by 40+ years.
Ryerson University Study (2016): Green roofs reduced stormwater runoﬀ by up to 65%.
National Research Council of Canada: Green roofs reduce peak summer temperatures by 2–3°C. An average annual runoﬀ reduction rate of 67% was recorded for a green roof in Toronto.

Key ﬁndings:

Stormwater capture lowers ﬂood risk.
Cooler rooftops reduce energy consumption.
Green roofs increase urban biodiversity.
Positive mental health eﬀects for building occupants with green views.

Policy Options

Recommendations

Launch a green roof pilot project at Allendale Long-Term Care Home.
Develop an implementation roadmap aligned with Halton’s climate action plan.
Explore funding sources such as FCM’s Green Municipal Fund and CMHC retroﬁt grants.
Amend regional planning policies to support green infrastructure retroﬁts.

Implications

If adopted, these measures would:

Improve stormwater management and reduce infrastructure repair costs.
Enhance resident comfort, particularly in long-term care homes.
Strengthen Halton’s reputation as a climate-forward region.
Provide actionable data for wider-scale rollouts across Ontario.

Conclusion

Green roofs present a practical, multi-beneﬁt solution to some of Halton Region’s most urgent climate infrastructure challenges. With leadership and collaboration, Halton can transform unused rooftop space into climate assets. We recommend starting small, with a high-impact pilot, and scaling quickly with policy support.

References

Berardi, U. (2016). The outdoor microclimate beneﬁts and energy saving resulting from green roofs retroﬁts. Energy and Buildings, 217-229.

Cascone, S., Catania, F., Gagliano, A., & Sciuto, G. (2018). A comprehensive study on green roof performance for retroﬁtting existing buildings. Building and Environment, 227-239.

Herath, M. (2024, January 11). Retroﬁtting Green Roofs: An Eco-Friendly Solution for Urban Buildings.

Retrieved from Eco Living Journey: https://ecolivingjourney.com/retroﬁtting-green-roofs/

In Our Nature. (n.d.). Top Drought-Tolerant Native Plants. Retrieved from In Our Nature: https://www.inournature.ca/top-drought-tolerant-native-plants-ontario

Intermountain Roofscape Supply. (2024, March 1). Sedum Roof: Weighing the Pros and Cons for Safe and Sustainable Design. Retrieved from Intermountain Roofscapes Supply: https://intermountainroofscapes.com/sedum-roof-pros-and-cons.html

Kenley, M. (n.d.). Recommendations for Municipalities: Focus on the Construction of Green Roofs. Toronto: Canadian Environmental Law Association.

Liu, K., & Minor, J. (2005). Performance evaluation of an extensive green roof. Toronto: National Research Council of Canada.

Luckett, K. (2009). Green Roof Construction and Maintenance, 1st Edition. The McGraw-Hill Companies, Inc.

MacIvor, J., Margolis, L., Perotto, M., & Drake, J. A. (2016). Air temperature cooling by extensive green roofs in Toronto, Canada. Ecological Engineering, 36-42.

Sustainable Technologies Evaluation Program. (2016). Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide. Toronto: Toronto and Region Conservation Authority.

Talebi, A., Bagg, S., Sleep, B. E., & O'Carroll, D. (2019). Water retention performance of green roof technology: A comparison of Canadian climates. Ecological Engineering, 1-15.

United States Environmental Protection Agency. (2025, June 26). Using Green Roofs to Reduce Heat Islands. Retrieved from EPA.gov: https://www.epa.gov/heatislands/using-green-roofs-reduce- heat-islands