PhD Oral Exam - Mohammad Seyedabadi, Building Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

The construction sector is one of the largest contributors to global greenhouse gas (GHG) emissions, accounting for nearly 40% of energy-related CO₂ emissions. While Life Cycle Assessment (LCA) has emerged as the principal methodology for quantifying the environmental impacts of buildings, most existing research is limited to single-building analyses and focuses primarily on operational emissions. Embodied and end-of-life phases remain underexplored, particularly at the district and city scale where data scarcity, methodological gaps, and high uncertainty present major challenges. This thesis addresses these shortcomings by developing and applying an integrated framework that combines Urban Building Energy Modeling (UBEM) with whole life cycle carbon assessment (WLCA), enabling comprehensive evaluation of embodied, operational, and end-of-life emissions across diverse building stocks.

The research begins with a systematic review of 150 studies on urban-scale LCA, identifying that the majority concentrate on operational emissions at the building scale, with only a fraction extending to whole-life system boundaries. Building on these insights, a cradle-to-grave LCA was conducted for a mixed-use district in downtown Montreal comprising 35 buildings. Localized embodied carbon factors for 55 materials were developed, and a novel methodology for end-of-life emissions was introduced, disaggregating demolition, on-site treatment, recycling, and landfilling. Results revealed that walls dominate both embodied and end-of-life emissions, and that end-of-life contributes consistently 5–7% of whole-life totals, validating yet refining assumptions in prior literature. Sensitivity analysis further demonstrated the significant influence of insulation material choices on overall performance.

The thesis then advances a structured framework for integrating LCA within the UBEM platform Tools4Cities, incorporating detailed models for embodied and end-of-life emissions alongside operational energy simulations. This integration enables district-scale workflows that account for building components, transportation, on-site construction activities, and retrofit impacts. Applied to the Montreal case, findings show that under a hydro-powered grid, embodied emissions can surpass operational emissions, challenging the prevailing assumption that operational carbon dominates.

Finally, the framework was extended to cover six common building typologies in Montreal under both hydro- and fossil-based grid scenarios. Results showed that under a hydro-dominated grid, A1–A3 embodied emissions account for 61–72% of totals, with operational emissions playing a secondary role. By contrast, under a fossil-fuel grid, operational energy overwhelmingly dominates, driving total emissions up to 22 times higher, particularly for energy-intensive typologies such as restaurants. These outcomes highlight the decisive influence of electricity grid carbon intensity in determining whether material decarbonization or operational efficiency should be prioritized.

Overall, this thesis delivers a novel, standard-aligned, and empirically validated framework for urban-scale whole life carbon assessment. It bridges UBEM and LCA, contributes new localized datasets and methodologies, and demonstrates through real-world application that carbon mitigation strategies must be context- and typology-specific. The findings provide actionable insights for policymakers, certification bodies, and urban planners: in low-carbon grids, material efficiency and durability are paramount, while in fossil-based contexts, operational energy and grid decarbonization remain decisive.