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Life Cycle Assessment (LCA) is a methodology used to quantify the impact of building construction supply chains on the environment in terms of measurable indicators such as Global Warming Potential. With climate pressures increasing, LCA offers a way to evaluate and reduce the embodied carbon of material selections through design and procurement.
With the accuracy of LCA dependent on a detailed system of material data, design take-offs, specifications, and documentation, it is most often applied in late design phases as opposed to in early design. Conducting LCA late in design, however, means that there are fewer opportunities for design teams to make substantial engineering changes in the façade approach or logic that may offer a more dramatic reduction of embodied carbon.
The paper and presentation will demonstrate an approach for conducting LCA during concept design and schematic design phases and highlight the opportunities that it presents for optimizing façade assemblies in the context of embodied carbon. This paper will present three project-based case studies of simple engineering and design moves that have a large impact in reducing embodied carbon of façade assemblies without compromising design intent or performance. The presented approach quantifies the Global Warming Potential of façade systems by considering module sizing and framing options from a structural performance perspective, mindful material selection, and repositioning of façade elements and units with respect to the building’s main structure.
These case studies will cover preliminary engineering judgments and estimations as well as the integration of parametric design tools such as the LCA Toolkit within the open-source Buildings and Habitats object Model (BHoM) to support early analyses.
The findings will illustrate the vast range of reductions available which can influence the carbon footprint of façade systems from as early as concept design phase, with some available reductions of up to 40% in embodied carbon.
According to The Global Status Report for Buildings and Construction, emissions from the buildings and construction sector amount to 39% of global CO2 emissions when accounting for both embodied and operational carbon with at least 11% attributed to embodied carbon impacts alone (Global Alliance for Buildings and Construction, United Nations Environment Programme 2020). The AEC sector’s impact on the current Climate Emergency, as well as its recent decline in decarbonization efforts (United Nations Environment Programme 2020) denote the urgency to implement greater efforts in delivering designs with lower embodied and operational carbon.
Within its Global Roadmap, the report lists low awareness of potential impact and options as the main issue within the materials category and therefore refers to raising awareness and promoting material efficiency as pathways toward improved decarbonization efforts within the building sector.
In recent years, contemporary Façade System have become continually more complex. Driven by performance criteria, facades carry an ever-increasing number of components, material layers, and bespoke interfaces. This challenges the possibility of implementation of embodied carbon quantification during early project design phases, such as Schematic and Concept design, as many of the required façade systems components and elements are not fully rectified and realised until later stages of project design and engineering.
Current approaches to embodied carbon quantification for façade assemblies and other building elements as discussed in the next section rely heavily on a great level of detail already produced for the system including finalized material and product selection. This directly and inevitably pushes the procurement of Life Cycle Assessment towards the later phases of building design, such as Design Development or Construction Documentation phases. This workflow is rather reactive in nature and does not allow for the ability to vastly change assemblies in order to impactfully reduce embodied carbon through system option vetting or modification.
The ability to implement LCA in the early design phases requires recognizing and applying simple yet impactful engineering changes which focus on material type, weight, and volume. These engineering changes are tracked for their impact on façade’s design intent as well as structural and thermal performances, to ensure that the system retains its integrity across all performative criteria.
The following case studies have been examined to present early design stage system engineering and option selection and the impact of these options on decarbonization as one of the main drivers. The case studies are based on popular and frequently utilized exterior wall systems, such as curtain wall, storefront, and punched window assemblies and are presented as applicable options for many projects, even if a clear carbon quantification or Life Cycle Assessment implementation has not been established.
Case Study 1 – 20 commercial story office building. Primary Façade type: Aluminum frame Unitized Curtain Wall. Frame engineering studies were carried out for material volume efficiency.
Case Study 2 – 2 story public services building. Primary Façade types: Metal panels and storefront. Structural loading calculations and LCA were carried out for mullion design efficiency.
Case Study 3 – 5 story educational building. Primary Façade types: Masonry. LCA was carried out to compare alternate glazing articulation designs for the punched openings.
To examine standard practice and motivation for LCA in contrast to those proposed in this paper, requirements published by green building certification systems including Leadership in Energy and Environmental Design
These case studies will cover preliminary engineering judgments and estimations as well as the integration of parametric design tools such as the LCA Toolkit within the open-source Buildings and Habitats
Building Type: 20 story tall commercial office tower
Project Location: Pittsburgh, PA
Main Façade Type: Unitized Curtain Wall
System under analysis: Unitized Curtain Wall
Description of engineering approach
Building Type: 2-story public services building
Project Location: New York
Façade Type: Masonry and Storefront
System under analysis: Storefront
Description of engineering approach towards material efficiency
Building Type: 5 story tall academic building
Project Location: New Jersey
Main Façade Type: Masonry
System under analysis: Glazing
Description of engineering approach towards material efficiency
Through the presented case studies we found that embodied carbon quantification during early design stages is not only possible but is a powerful, proactive approach to reduce embodied carbon within
The authors wish to thank the BuroHappold’s Computational Design, Façade Engineering, and Sustainability teams for their support as well as for an inspiring and ever fruitful collaboration.
Carbon Leadership Forum. “LCA Practice Guide”. Carbon Leadership Forum. April 28, 2020.
Hughes, Emma. “How LEED v4.1 addresses embodied carbon.” U.S. Green Building Council. Accessed October 16, 2021. https://www.usgbc.org/articles/how-leed-v41-addresses-embodied-carbon
International Living Future Institute. “Zero Carbon Certification”. https://living-future.org/zero-carbon-certification/
Lew, Vikki. “Establishing a Life Cycle Assessment Methodology for Innovative Façade.” Façade Tectonics Institute
United Nations Environment Programme (2020). 2020 Global Status Report for Buildings and Construction: Towards a Zero-emission, Efficient and Resilient Buildings and Construction Sector. Nairobi
U.S. Green Building Council. “LEED Reference Guide for Building Design and Construction.” Version 4. 2013.
Anderson, Jane “Estimated Global Embodied Carbon of Construction Materials”, January 13, 2016 https://constructionlca.co.uk/2016/01/13/estimated-global-eco2-construction-materials/