Building decarbonization: The importance of circularity, material selection and innovative construction methods

Traditionally, the mantle of decarbonization strategies has been borne by designers, architects and planners, whose innovative approaches to sustainable design have paved the way for reducing the environmental impact of the built environment. However, it's becoming increasingly clear that general contractors also wield a significant and transformative power in this realm.

Responsible for executing the visions of designers, contractors occupy a central position in the construction value chain and h­­­ave a tremendous responsibility and opportunity to drive this transformation. A wealth of strategies exists to help contractors reduce projects’ embodied carbon, the upfront carbon emissions associated with materials and construction processes throughout a building 's lifecycle.

Here are some key strategies:

Maximize opportunities for adaptive reuse of buildings

A staggering 82 billion square feet, or roughly one-quarter of existing buildings today, are expected to be demolished and replaced between 2005 and 2030. While there is a need for new construction, it is crucial to maximize the opportunities for adaptive reuse, which refers to the practice of creatively transforming existing buildings and structures for new uses, rather than demolishing them and constructing new ones.

Building reuse almost always yields fewer lifecycle environmental impacts than new construction when comparing buildings of similar size and functionality. It can take between 10 and 80 years for a new, energy-efficient building to overcome, through more efficient operations, the negative climate change impacts created during the construction process. Therefore, it is important to utilize opportunities for adaptive reuse.

Skanska recently completed the University of Portland’s Shiley-Marcos Center for Design & Innovation in Portland, Oregon, which is a great example of adaptive reuse. This project reuses the main structural system of a previously existing physical plant located on campus, turning it into a hub for academic creativity and learning for students, faculty, and community.

An adaptive reuse strategy and reuse of the main structural system greatly reduced the amount of new concrete and rebar and achieved a 42% reduction in embodied carbon emissions compared to a new construction alternative.

Reduce embodied carbon emissions through circularity and material reuse

Circularity offers a powerful solution to tackle embodied carbon emissions in the construction industry. Closing the loop on material lifecycles, eliminates the need to extract, process and transport virgin materials, while reducing waste generation.

The Portland International Airport's Terminal Core Redevelopment project, built by the Hoffman-Skanska Joint Venture, exemplifies this approach. Pursuing LEED® Gold certification, the project features an iconic nine-acre long-span mass timber roof constructed from wood sourced from local and regional forests, promoting sustainability in aviation infrastructure.

The project team also implemented circularity strategies and engaged with local recyclers to transform the project’s wood waste into finished products and wall panels, minimizing landfill use, and utilizing salvaged lumber for miscellaneous needs, reducing overall reliance on virgin materials.

Moreover, instead of building a new temporary bypass during the 5-year long construction, the team creatively relocated and repurposed the 18,000-ton Concourse Connector as a temporary bypass passageway to enhance airport passenger experience and help people move safely around the construction area at the airport’s core.

These reuse strategies positively contribute to the project’s sustainability goals to prevent waste and reduce the embodied carbon footprint of the project while achieving significant cost and time savings.

Procure low-carbon materials and transition to low-carbon construction

General contractors play a vital role in informing design choices and procuring low carbon alternatives, identifying opportunities to minimize transportation and construction carbon emissions, and tracking the realized embodied carbon impacts at project completion.

Skanska co-conceived and developed the Embodied Carbon in Construction Calculator (EC3) tool in partnership with the Carbon Leadership Forum and nearly 50 industry partners, including Microsoft, to tackle embodied carbon in our value chain. This free, open-access tool is helpful for AEC professionals, particularly general contractors, enabling them to make low-carbon procurement and smart transportation and construction decisions.

Skanska’s recently completed  development project in Texas, 1550 on the Green, is a great example of the power of the EC3 tool. This Class-A office building achieved LEED® Platinum, WELL Platinum, and WiredScore® Platinum certifications and utilized the EC3 tool which allowed Skanska to identify low carbon materials and reduce the project’s embodied carbon emissions by approximately 45%.

Contractors can easily identify low-cost and no-cost solutions for low-carbon materials and achieve such embodied carbon savings at cost premiums of less than one percent.

Tackling the emissions on construction sites is crucial for general contractors to reduce their environmental impact. Skanska started to switch from using petroleum diesel to renewable diesel in construction equipment and vehicles in select projects on the West Coast and has been expanding the use of the alternative fuel to other regions and projects.

Renewable diesel is nearly chemically identical to petroleum diesel. According to the California Air Resources Board, using renewable diesel provides a 40-50 percent reduction of GHG from well-to-wheel emissions and produces specific measurable reductions in tail-pipe emissions versus fossil-based diesel.

As part of its climate plan, Skanska is also in the process of piloting pre-production models of various pieces of all-electric equipment and all-electric vehicles in select sites to further reduce its emissions on construction sites.

The path to decarbonization is paved with collaboration and innovation, and contractors hold a significant responsibility. Through circular practices, smart material choices, and innovative construction methods, contractors can significantly contribute to the sustainability of the built environment. Ignoring this responsibility isn't just an ethical misstep, it's a business risk.