Material quantities in building structures and their environmental impact

Abstract

Improved operational energy efficiency has increased the percentage of embodied energy in the total life cycle of building structures. Despite a growing interest in this field, practitioners lack a comprehensive survey of material quantities and embodied carbon in building structures. This thesis answers the key question: "What is the embodied carbon of different structures?" Three primary techniques are used: (1) a review of existing tools and literature; (2) a collaboration with a worldwide network of design firms through conversations with experts and (3) the creation of a growing interactive database containing the material efficiency and embodied carbon of thousands of buildings. The first contribution of this thesis is to define challenges and opportunities in estimating greenhouse gas emissions of structures, expressed in carbon dioxide equivalent (CO₂e). Two key variables are analyzed: material quantities (kgmaterial/m² or kgm/m²) and Embodied Carbon Coefficients (ECC, expressed in kgCO2e/kgm). The main challenges consist of creating incentives for sharing data, identifying accurate ECCs and resolving transparency while protecting intellectual ownership. The main opportunities include using Building Information Models to generate data, proposing regional ECCs and outlining a unified carbon assessment method. The second contribution is the development of an interactive online tool, called deQo (database of embodied Quantity outputs), to provide reliable data about the Global Warming Potential of buildings (GWP, measured in kgCO2e/m² and obtained by multiplying the two key variables). Given the need for a long-term initiative, a framework is offered to create an interactive, growing online database allowing architects, engineers and researchers to input and compare their projects. The third contribution is the survey of 200 existing buildings obtained through deQo. Two general conclusions result from this survey of building structures: material quantities typically range from 500 to 1500 kg/m² and the GWP typically ranges between 200 and 700 kgCO2e/m2. Conclusions from this survey include that healthcare buildings use more materials whereas office buildings have a lower impact. Additionally, specific case studies on stadia, bridges and skyscrapers demonstrate that the design approach can have a significant impact on the embodied carbon of building structures. Ultimately, this thesis enables benchmarking of the environmental impact of building structure