Designing to reduce a building’s embodied carbon

by nithya_caleb | January 17, 2020 5:00 am

by Stephanie Fargas

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The carbon footprint of the design and construction industry reaches far beyond the boundaries of a single building or site. Due to various processes, ranging from the extraction of raw materials to manufacturing and installation of the construction materials, the impact of a single project includes both embodied carbon within the built environment and operational carbon generated throughout the life cycle of the structure. Embodied carbon is defined as the carbon dioxide (CO₂) emitted during the full life cycle of a product from extraction (cradle) to the use and disposal phases (grave).

Construction products contribute to 11 per cent of global greenhouse gas (GHG) emissions (For more information, read the 2017 and 2018 United Nations (UN) Environmental Global Status reports.). Canada’s GHG emissions from the built environment is 17 per cent (residential, commercial, and institutional buildings) (Consult the 2016 Pan-Canadian Framework on Clean Growth and Climate Change.). There has been significant strides in reducing operational carbon by improving the energy efficiency of mechanical and electrical systems, and integrating renewable energy resources. However, designing to reduce embodied carbon has not been an area of emphasis in the design community, or a mandatory policy in Canada.

With recent efforts from Architecture 2030 (the American Institute of Architects [AIA] 2030 and 2050) and sustainability certification programs, such as the Leadership in Energy and Environmental Design (LEED), Envision, and the Living Building Challenge (LBC), awareness has been raised on the importance of designing for low embodied carbon to address climate change.

This lack of emphasis has not prevented the design and construction industries from taking heed of the urgency of the current climate crisis or from utilizing available tools to plan and execute buildings that are both beautiful and low-carbon or carbon-neutral. In fact, the opportunities for these industries to become leaders in carbon solutions are just beginning to be tapped. This article focuses on how the industry can design for low embodied carbon solutions in new and existing buildings.

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Architecture 2030 was established by AIA in 2006 to address climate change through sustainability-driven solutions and carbon-neutral design in the built environment. It established targets toward zero emissions including a 70 per cent reduction in GHG related to energy consumption below a comparable building type for new and existing structures in specific geographical locations. Since its establishment, more than 1200 design, architecture, and engineering firms have signed on to monitor their progress toward the agreed-upon goal. Additional metrics were established for subsequent years—for example, by 2020 an 80 per cent reduction, 90 per cent in 2025, and carbon-neutral in 2030 (i.e. complete elimination of fossil fuel sources from building operations). Further, AIA, the Royal Architectural Institute of Canada (RAIC), Ontario Association of Architects (OAA), U.S. Green Building Council (USGBC), Canada Green Building Council (CaGBC), and several countries, states/provinces, and cities have also advocated and adopted these policies. The CaGBC has developed the Zero Carbon Building Standard to address and achieve the climate change commitments Canada has signed onto and provide guidelines for zero-carbon design for new and existing buildings of various project typologies (e.g. institutional, commercial/office, residential, and commercial warehouses). Through this standard, projects are to demonstrate a net emissions balance of zero or less for building operations. Emissions generating GHG are offset by renewable energy sources on or offsite. Two projects have been certified as zero-carbon buildings—evolv1 in Waterloo, Ont., and Mohawk College’s Joyce Centre for Partnership and Innovation in Hamilton, and 16 projects are enrolled in the program. Currently, the Zero Carbon Building Standard is not mandatory, but rather a guideline for consultants and owners to follow.

Sustainability metrics

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Through its LEED v4 reference standard USGBC has introduced the Building Life-cycle Impact Reduction credit under the Materials and Resources category. The credit’s fourth option allows project teams to conduct a whole building life-cycle assessment (LCA) on the structure to demonstrate a minimum 10 per cent reduction compared to a baseline facility in at least three of the following six impact categories:

• global warming potential (GWP);
• depletion of the stratospheric ozone layer;
• acidification of land and water resources;
• eutrophication (addition of nitrogen or phosphate entering into a water source as run-off causing accelerated aquatic plant growth and depleted oxygen levels);
• formation of tropospheric ozone; and
• depletion of non-renewable energy sources.

It is important to note the GWP category is mandatory. Additionally, no impact category assessed as part of the LCA may increase by more than five per cent compared to the base building.

With LBC, the International Living Future Institute (ILFI) requires projects to account for the total embodied carbon (tCO₂e) impact from its construction with a one-time carbon offset from an approved provider, through Imperative 11 – Embodied Carbon Footprint. To comply, the project team is to incorporate carbon-reduction strategies during the design phase, and then purchase certified emissions reductions (CERs), carbon offsets through the institute’s new Living Future Carbon Exchange, or another acceptable third-party verified program to nullify 100 per cent of the CO₂e.

The Institute for Sustainable Infrastructure’s (ISI’s) Envision program has a credit under Emissions—Credit CR1.1 Reduce Greenhouse Gas Emissions requires at a minimum a life-cycle carbon analysis and assessment to reduce the project’s anticipated net GHG. This credit offers teams various levels of achievement from ‘improved’ to ‘restorative’, with the latter being the highest, resulting in the project being classified as carbon negative (i.e. sequestering more carbon than produced).

From LCA to environmental product declarations (EPDs), there are various sources and methods of documentation for a project team to determine embodied carbon. An LCA serves as a tool for understanding the energy use intensity (EUI) and environmental impacts by considering all aspects of a building from extraction of raw materials used for construction, manufacturing and installing products, and decommissioning of the building, similar to the cradle-to-grave approach. The European standard EN 15978:2011, Sustainability of Construction Works – Assessment of Environmental Performance of Buildings, is used for whole building LCA. It identifies the calculation method and reporting requirements. In EN 15978, LCAs are conducted to determine the environmental impact of a product or building based on the six impact categories (Figure 1).

Environmental product declarations

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EPDs with the supporting product category rule (PCR) and LCA contain information that can be utilized to determine whether a product can be incorporated into the project to reduce embodied carbon and its contribution toward the environmental impact categories. Before an EPD can be created a PCR is developed to define scope, impact categories, and measurement methods. PCR can be created through assistance and guidance from industry leaders such as associations, governments, and reference standard committees. PCRs are meant to be objective, defining documents serving as the framework for conducting LCAs. PCRs help promote fairness by ensuring all the similar products are measured with the same metrics. PCRs are often initiated as a request from a manufacturer wanting to develop a product-specific EPD. This request is sent to a program operator such as:

• ASTM International;
• ICC Evaluation Service (ICC-ES);
• Institute for Environmental Research and Education (IERE);
• NSF International;
• SCS Global Services; and
• Underwriters Laboratories (UL) Environment (Figure 2).

An EPD conforms to the International Organization for Standardization (ISO) 14025: 2006, Environmental labels and declarations – Type III environmental declarations – Principles and procedures, ISO 14040: 2006, Environmental management – Life cycle assessment – Principles and framework, ISO 14044: 2006, Environmental management – Life cycle assessment – Requirements and guidelines, and EN 15804:2012, Sustainability of Construction Works – Environmental Product Declarations – Core Rules For The Product Category Of Construction Products, or ISO 21930: 2017, Sustainability in buildings and civil engineering works – Core rules for environmental product declarations of construction products and services. EPDs are classified into two main categories:

• industry-wide (generic) – type III; or
• product-specific – type III.

Type III means the product has been verified and certified by a third-party program operator. An industry-wide EPD is verified and is generic to a product type (e.g. gypsum board) but is not specific to a manufacturer. For eligibility, manufacturers are to provide representation in the EPD development either directly or through the program operator. A product-specific EPD is verified and is distinct to a manufacturer as it reflects particular aspects of the production process. These EPDs can be used to conduct a whole building LCA. If a project team wants a specific basis-of-design product, a product-specific EPD can be utilized to research a particular manufacturer’s environmental performance.

When a design team chooses to establish low embodied carbon as criteria for a project, it is important to set targets, develop a strategy for achieving the goals, prioritize products and materials that will be assessed to determine their embodied carbon contribution and potential reduction, and conduct a building LCA. Some strategies include but are not limited to:

• identify the project goal for embodied carbon and the scope of LCA (e.g. what components will be included in the LCA);
• determine the LCA tool and life-cycle inventories (LCI) data source to use;
• identify products’ and building components’ ‘hot spots’ (i.e. highest impact potential) that can contribute to reduction in embodied carbon;
• evaluate the different material types, estimated quantity for each, and anticipated service life;
• explore the possibility of reusing the building structure and/or salvaging building materials to reduce embodied carbon;
• assess options for the material of the building structure to optimize design, utilizing renewable resources (carbon sequestering opportunities) for structures such as heavy timber, or incorporate recycled content such as fly ash or CO₂ as an additive alternate to Portland cement to optimize the concrete mix design; and
• design buildings for long service life expectancies (e.g. 50 to 100 years).

When conducting an LCA it is important to maintain consistency in the tool being utilized, as LCI sources vary within the tools and the data may not be comparable or classified differently. Similarly, if an EPD will be used, the referenced PCR needs to be the same amongst the EPDs being compared.

Tools in the market

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Numerous tools and resources are available to the design community to guide design choices, including:

• Architecture 2030 offers the ‘Carbon Smart Materials Palette,’ which is a guideline offering options for reducing emissions (it can be utilized when conducting an LCA and evaluating EPDs);
• Architecture 2030 also has the ‘EPD Quicksheet’ to simplify the review and evaluation of EPDs; and
• the Carbon Leadership Forum offers the ‘Life Cycle Assessment of Buildings: A Practice Guide,’ a guideline meant to assist the design community with understanding the purpose of an LCA and how to conduct one.

The design and construction industry can take the lead and facilitate market transformation. Additionally, clients can utilize LCAs to benchmark the sustainability performance and carbon footprint across their building portfolio, and identify areas of improvement.

The design and construction industry has an opportunity to holistically design buildings to reduce the impact of climate change by advocating for greater transparency in the embodied carbon data of building materials/products, incorporating sustainable design solutions with reduced embodied carbon, and establish embodied carbon as a primary design consideration as opposed to a secondary thought.

Case study

Designing for embodied carbon was a consideration in the University of Calgary – MacKimmie Complex and Professional Faculties Redevelopment project. It is also registered as a pilot project with the CaGBC Zero Carbon Building Program. During the schematic design phase, the consultant with participation and guidance from the owner’s representative conducted a facility assessment of the existing structure to determine opportunities for sustainable building repurposing. The evaluation included determining the inherent monetary value of the existing structure as well as the embodied energy of extraction of raw materials, transportation, construction of a new building, and demolition and disposal of the existing structure. A key consideration for calculating the embodied energy was to identify the regional and international differences in the measurement of embodied energy for material types—for example, reinforced concrete differs based on region, source/extraction methods of raw materials, energy sources, electrical production, and transportation. Once the assessment was completed it was determined retaining a significant portion of the structure allowed for a reduction in the embodied energy that would have been generated from a traditional design approach of demolishing the existing structure and constructing a new one.

Through an integrated design process the main project participants had contributed to identifying sustainable strategies to address embodied carbon. Products were evaluated on its anticipated service life and opportunities for optimizing the design.

[6]Stephanie Fargas is a specification writer for the Calgary office of Dialog with eight years of experience in a variety of project typologies. She works with Dialog’s specifications team developing project specs, conducting sustainable product research, and liaisoning between consultants. She leads the research and development of specifications for Dialog’s first Living Building Challenge (LBC) certification and the Leadership in Energy and Environmental Design (LEED) Platinum project, Bill Fisch Forest Stewardship and Education Centre in Ontario. Fargas can be reached at sfargas@dialogdesign.ca[7].

Source URL: https://www.constructioncanada.net/tools-of-the-trade-designing-to-reduce-a-buildings-embodied-carbon/

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