Counterfactual massings explore how the simplification of built form
through 1) a reduction of steps, and 2) an elimination of step-backs impact embodied carbon intensity. The
counterfactuals provide an estimated range of embodied carbon intensity.
The Atmospheric Fund
Mantle Developments
Life Cycle Assessment, Analysis & Reporting, Stakeholder Engagement, Policy Development
The City of Toronto’s Urban Design Guidelines (UDGs) have played a crucial role in shaping the form of our city’s built environment over the past decade. The Guidelines, and the built forms they have informed, have also played a critical role in determining both the operational and embodied carbon footprints of buildings. It is therefore critical that the UDGs are reviewed and revised in lock-step with the City’s ambitious Green Standards to support and enable future design and construction to meet the City’s world leading Net Zero 2040 commitments.
The Urban Design Guidelines study was initiated and undertaken to understand more clearly the impacts of the current Guidelines on embodied carbon emissions. The study uses ten projects across the City for a detailed case study analysis to understand how the application of the Townhouse & Low-Rise Apartment Guidelines (TLG), Mid-Rise Performance Standard (MG), and Tall Building Guidelines (TG) may unintentionally contribute to higher embodied carbon emissions in building construction and streetscape development, and how revisions and modifications to these could support the significant embodied carbon reductions.
To ground the study, Ha/f conducted extensive engagement with City representatives through a project Steering Committee and Working Group that included members from Urban Design, Environmental Planning, Transportation Planning, and Solid Waste Management departments. Throughout the project’s duration, the Steering Committee met bi-monthly to review progress and provide feedback. Ha/f conducted detailed life cycle assessments (LCA), comparative studies, and counterfactual studies of the case study buildings across the three primary building categories of Low-Rise, Mid-Rise, and Tall buildings (Table 1). The study correlates these findings with corresponding UDGs, demonstrating where impacts on embodied carbon emissions occur, and identifies opportunities for high impact revisions.
Recommendations reflect these assessments, and serve to inform future revisions to support the decarbonization of the GTHA’s built environment. Where applicable, recommendations also take into account other quantifiable impacts such as operational emissions, construction costs, and microclimate.
Key Reccomendations
- Performance-based, not Form-based Guidelines. Establish performance-based guidelines with quantifiable metrics where possible in place of form-based guidelines. Allow project teams to demonstrate compliance with key Urban Design concerns through quantifiable metrics instead of prescribing a form-based solution to achieve a desired outcome.
- Disincentivize Underground Construction. Municipalities incentivize the creation of basements through bylaw exemptions, height restrictions, and parking requirements. Underground construction has a disproportionately high embodied carbon footprint due to the additional shoring and retention structure required and are at increasingly higher risks of flooding and pose a long-term liability to building owners.
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Optimize Window-to-Wall-Ratios. Across all study projects the highest contributor to embodied carbon in building facades were windows and glazing systems. When viewed across the whole life of projects, this factor can double or triple depending on the expected service life of the system. Additionally, windows and glazing are the locations of greatest thermal heat loss and solar heat gain and are the greatest contributors to operational emissions
Key Outcomes
- The Study’s recommendations informed revisions of Mid-Rise Building Design Guidelines, passed by Council in December 2024.
- The Embodied Carbon Management Toolkit provides summary recommendations for Municipal staff to understand and implement changes to design guidelines.
- Recommendations related to massing, parking, and public realm have led to further City-led initiatives to investigate alternatives.
Resources