Embodied Carbon in Residential Structures A Toronto based case study

Case Study | Sept 12, 2023
RJC Engineers | BDP Quadrangle 

SUMMARY
Embodied carbon, released during building manufacturing and construction, is a critical environmental measure. Often overshadowed by operational carbon, its significance grows with building efficiency improvements. Emissions, mainly during construction, coincide with a crucial period for climate risk mitigation.

The purpose of this study is to inform policy makers, industry professionals, citizens, and any other relevant or interested stakeholders, of the issues which need to be addressed and the background information to make educated decisions to impact meaningful change.

1. INTRODUCTION
Embodied carbon is the amount of carbon dioxide and other greenhouse gases that are emitted during the manufacturing, transportation, and construction of a building or infrastructure project. It is a critical measurement of a structure’s environmental impact. Embodied carbon is often overlooked in favor of operational carbon, which is the carbon footprint of a building during its use. However, as building operation becomes more efficient, embodied carbon will become increasingly important. Additionally, most embodied carbon emissions occur during the building construction stage - in the present and near future. Scientists have identified this time period as critical in terms of the required actions needed to avoid crossing a line which will potentially put millions more people at risk of life-threatening heat waves and poverty [1].

Architects, engineers, and other building professionals are increasingly looking to reduce embodied carbon in their design and construction decisions via more conscientious material choices, efficient building techniques, and other strategies. As this is an emerging field, recommended best practices and guidelines for determining the embodied carbon within a structure need to have increased exposure in the design community.

BDP Quadrangle initiated a study with their structural engineering counterparts to examine the embodied carbon of four current projects in the Greater Toronto Area. BDPQ’s main driver was that architects and engineers can have a stronger impact when working together. It is pragmatic for architects to work with their consultants on solutions that can be executed from both ends. This way, joint workflows can be fine-tuned, EPDs can be agreed upon, and standards can be followed. The environmental goals of each firm can then be aligned moving forward. Both the structural and architectural teams for each project calculated the embodied carbon of the structure and substructure. The focus of the study was the structure and substructure as together they account for 40-70% of the overall embodied carbon of a building [2].

The built environment has a tremendous impact on our climate. According to Architecture 2030, the built environment is a major contributor to global CO2 emissions, accounting for 40% of the annual total. This includes both building operations, which contributes 27% annually, and embodied carbon, which contributes another 13% annually [3]. Additionally, production of three materials—concrete, steel, and aluminum—contribute to a significant portion of global emissions (23%), with most of their usage occurring in the built environment. Looking ahead to future construction projects until 2040, it becomes evident that embodied carbon plays a crucial role in carbon emissions. Unlike operational carbon emissions that can be reduced over time through energy upgrades and renewable energy adoption, embodied carbon emissions become fixed as soon as a building is constructed. By focusing on reduction of operational carbon of new buildings, embodied carbon will account for a higher proportion of whole life carbon of a building [2]. According to LETI, structural elements constitute as the largest percentage of embodied carbon in a building. Thus, greatest embodied carbon reductions can be achieved by focusing on structures [2].

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