Whole-Life Carbon

A significant portion of carbon emissions can be attributed to the construction of a building. For a typical building, embodied carbon makes up 40-60% of a building’s total carbon footprint over the first 30-years. This is further magnified with high performance or ZNE buildings that have low to zero operational carbon emissions and embodied carbon can make up to 100% of the building’s carbon footprint. Our current methods of design and construction do not adequately account for the embodied carbon impacts which are released prior to a building’s operation. There is an urgent need to address our embodied carbon impacts where the savings can be significant and realized immediately. The near-term reduction of carbon is most valuable to meet our long-term climate targets and avoid further climate disaster.

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Defining
Embodied Carbon

 

Embodied carbon or “upfront carbon” refers to the greenhouse gas emissions from the extraction, manufacturing, transportation, installation, maintenance, and disposal of building materials. In contrast, operational carbon refers to the greenhouse gas emissions due to building energy consumption.  

Source: Carbon Leadership Forum 

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Our Approach

The Case Study accounts for its carbon emissions over a typical building life cycle, not just starting on the first day of building operation. For our buildings to attempt to approach true net-zero carbon, operational carbon must be optimized in tandem with embodied carbon, the use of refrigerants, and the landscape and site design.

We assess all design options over a typical 60-year life span, factoring in maintenance and equipment replacement schedules, refrigerant leakage rates, landscape sequestration and site maintenance. The Case Study achieves a 68% reduction, saving 4,458 Metric Tons of Carbon Dioxide equivalent emissions (CO2e) over its lifespan compared to a baseline building situated in San Francisco. When moving to Atlanta, it achieves a 69% reduction, saving 8,967 Metric Tons of CO2e.


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The Mass Timber Graduate Housing Case Study utilized life-cycle assessment and supply chain optimization tools to benchmark, optimize and vet design decisions and material choices throughout each design stage. The design process started with a largely mass timber structure. A timber structural system introduces a multitude of synergistic benefits as the result of its lightweight, precision shop fabrication, and reduced erection schedule. All while producing significantly less waste and providing long-term carbon sequestration in a beautiful and renewable material. The carbon storage potential of the timber structure provides the basis for a building seeking to achieve carbon neutrality over its lifespan.  

Once the design was optimized to maximize efficiency of the structure, minimizing the size and volume of structural elements, sourcing and procuring the materials presents the next challenge for the team. Procurement and product selections that optimize for low-embodied carbon will utilize the Embodied Carbon in Construction (EC3) tool. 

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Sustainable Tools

Embodied Carbon in Construction Calculator (EC3 Tool)

In 2019, Perkins&Will joined as pilot partners to the Embodied Carbon in Construction Calculator (EC3) tool. Developed by Building Transparency in conjunction with the Carbon Leadership Forum and C-Change Labs, EC3 took on an ambitious and long-elusive goal to compare and reduce embodied carbon emissions from construction materials through supply chain transparency and optimization. This free, open-access tool for architects, engineers, owners, construction companies, building material suppliers and policy makers continues to transform how the AEC industry procures low-carbon construction materials.

Material Health

The Perkins&Will Precautionary List identifies the most ubiquitous and problematic substances to be avoided in the built environment. It has been compiled to demand transparency from manufacturers and help design professionals make informed decisions about the materials and products we use in our buildings. The Perkins&Will Precautionary List will inform finish selections to eliminate substances known to have negative health impacts, thus reinforcing the project commitment to the support and protection of human health.

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In addition to mass timber, the low-carbon materials palette includes concrete with carbon that is reduced through supplementary cementitious materials (SCMs) and steel from renewably powered, electric arc furnace mills. While the building’s structure and enclosure make up a significant portion of the embodied carbon of the building, attention to product selection across the entire design process ensured that an optimized carbon approach was applied throughout. 

Life Cycle Assessment (LCA) quantifies the relative embodied carbon of the major materials proposed for the building broken down into the carbon from extraction through manufacturing, transportation, use, replacement, and end-of-life. This can help designers to choose between variables around sourcing of materials to maximize carbon reduction. For example, due to its high energy intensity, sourcing electric-arc-furnace steel from an out-of-state supplier may still provide a significant reduction compared with sourcing conventionally made steel from a local supplier.  

The manufacturing, construction, and eventual decommissioning of the materials of the Case Study Design will produce approximately 1,060 Metric Tons of CO2 as compared with 3,283 Metric Tons of CO2 for a baseline building; this results in a 68% reduction of CO2e before supply chain procurement optimization.